Removal of Physical Materials from Systems

8.07 Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats VH Rivera-Monroy, RD Delaune, and AB Owens, Louisiana State University, Baton Rouge, LA, USA J Visser, University of Louisiana at Lafayette, Lafayette, LA, USA JR White and RR Twilley, Louisiana State University, Baton Rouge, LA, USA H Hernandez-Trejo, Universidad Juárez Autónoma de Tabasco, Villahermosa, Mexico JA Benitez, Universidad Autónoma de Campeche, Campeche, Mexico © 2011 Elsevier Inc. All rights reserved. 8.07.1 8.07.1.1 8.07.1.2 8.07.2 8.07.3 8.07.3.1 8.07.3.1.1 8.07.3.1.2 8.07.3.1.3 8.07.3.2 8.07.3.2.1 8.07.3.2.2 8.07.3.2.3 8.07.3.2.4 8.07.3.3 8.07.3.3.1 8.07.3.3.2 8.07.3.3.3 8.07.3.3.4 8.07.3.4 8.07.3.5 8.07.3.5.1 8.07.3.5.2 8.07.3.5.3 8.07.3.5.4 8.07.3.5.5 8.07.3.5.6 8.07.3.5.7 8.07.3.5.8 8.07.3.5.9 8.07.4 References Introduction Current Wetland Global Extent and Loss Human Impacts on Wetland Area Restoration and Rehabilitation: Why Semantics Matter When Addressing Loss of Area and Habitat in Wetland Ecosystems Case Studies Mississippi River Delta, Louisiana, USA Hurricane effects on coastal wetland loss Influence of coastal restoration efforts on reducing wetland loss Human impact GMU Delta Region, Tabasco–Campeche, Mexico Hydrology and loss of space Human Impacts Mangrove wetlands GMU ecological and economic importance The Netherlands History of wetlands in the Netherlands Wetland hydrology Wetland types and current threats Climate change Puerto Rico Island Everglades, South Florida, USA Kissimmee River Lake Okeechobee Everglades Agricultural Area Stormwater treatment areas Water Conservation Areas The Everglades National Park Restoration issues Successful restoration The fight for water Summary and Final Comments 186 187 188 190 192 192 193 193 195 197 198 199 200 200 200 200 201 202 202 203 206 207 207 208 208 208 208 208 209 209 209 212 Abstract The wide spatial distribution of wetlands (e.g., swamps, bogs, marshes, and mires) across different latitudes and geomor­ phological settings reflects their complex biotic and abiotic interactions that define their ecological function and high economic value. As space becomes more limited, and landscape fragmentation increases, competition over land area for development and related human activities will certainly limit management options/decisions related to the conservation and rehabilitation/restoration of wetland ecosystems, especially at large spatial scales. In this chapter, we draw information from multiple sources and experiences to compile a series of case studies to focus our attention on characterizing the direct and indirect causes of wetland degradation and loss, particularly in coastal regions. The examples used in this chapter include deltaic regions (Mississippi River Delta, Louisiana, USA; Grijalva–Mezcalapa–Usumacinta, Mexico; and Central Coast, Netherlands), islands (Puerto Rico), and karstic platforms (Everglades, FL, USA). Current estimates of global wetland area range from 6.8 to 10.1 million km2, which represents 5–8% of the Earth (56% in tropical and subtropical regions). Loss of approximately 50% of wetlands around the world indicates the significant effect of human activities. Practices such as 185 186 Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats excessive harvesting, hydrological modifications and seawall constructions, coastal development, and pollution are some of the most pressing causes of wetland loss. Similarly, inland wetlands have been impacted by constant hydrologic modification and agriculture and urban development. The examples presented in this chapter underline the dynamic interaction between human actions and wetland habitat reduction at local and global scales. These issues define well the scope of ‘human use and abuses’ of productive ecosystems vital for the sustainability of both poor and rich nations. However, present political, social, and economic structures in most of the coastal regions around the world are disconnected from the actual functioning of the natural environment in which they reside, hindering conservation of productive wetland ecosystems. 8.07.1 Introduction Wetlands are a major feature of the landscape in all parts of the world. Their wide geographic distribution in coastal and inland regions makes them one of the most diverse and productive ecosystems. Human societies have historically thrived in asso­ ciation with these habitats due to the abundance of ecological goods and services. Yet, despite these benefits to humans, such areas are currently some of the most degraded ecosystems on a global scale. The spatial distribution of wetlands (e.g., swamps, bogs, marshes, and mires) across different latitudes and geo­ morphological settings reflects their complex biotic and abiotic interactions that define their ecological function and economic value. Despite the wide distribution of wetlands, worldwide losses are regionally dependent and strongly associated with the intensity of human impacts. As a result of the increasing awareness over the last 20 years regarding the negative impacts of human activities on the quality and quantity of wetlands and their ecological goods and services, it is apparent that direct wetland loss represents one of the major threats to their sustainability. Some of the most recognized goods and services provided by wetlands include habitat for commercial and recreational fish and shell­ fish, flood mitigation and storm surge abatement, improvement of water quality, and aesthetic and recreational value (Soderqvist et al., 2000; Turner et al., 2000). Extensive work is currently performed to document not only the actual economic benefits associated with maintaining wetlands in their original state, but also the approaches/methods needed to restore/rehabilitate their ecological structure and function (Englehardt, 1998; Gutrich and Hitzhusen, 2004; Ramachandra et al., 2005; Milon and Scrogin, 2006; Costanza et al., 2008; Dodds et al., 2008; Chen et al., 2009). Despite the apparent reduction in wetland loss rates in the last 10 years in developed countries (e.g., the USA, Mitsch and Gosselink, 2007) and increased awareness regarding their economic sig­ nificance in developing countries (Crisman, 1999; Chen et al., 2009), there is still a net loss, which is now exacerbated by the negative impacts of global climate change and a rise in sea level. Indeed, we are facing new challenges not only due to the increasing demand of natural resources from imperiled wetland ecosystems, but also due to the crude and irreversible wetland loss currently taking place in subtropical and tropical regions (e.g., Dewan and Yamaguchi, 2009). As space becomes more limited, and landscape fragmenta­ tion increases, competition over land area for development and related activities will certainly limit management options/deci­ sions related to the conservation and rehabilitation/restoration of wetland ecosystems, especially at large spatial scales. We believe that many solutions are dependent not on the lack of scientific information, but on the tremendous challenge of finding a balance between quality of life in sustainable ecosystems and the necessary economic drivers to support them. There are excellent reviews about the origins, distribu­ tion, and current extension of wetland areas around the world. For example, the books by Fraser and Keddy (2005), Mitsch and Gosselink (2007), and Mitsch et al. (2009) offer a recent analysis of the state of knowledge in several ecological processes and management issues, ranging from the complex interaction of environmental variables regulating wetland productivity to wetland creation and restoration strategies, including the need to devise wetland protection laws that cross international boundaries. Several publications have offered a comprehensive review of the chemical and biological cycling of nutrients, trace elements, and toxic organic com­ pounds in wetland soils and water column as related to water quality, carbon sequestration, and greenhouse gasses (e.g., Reddy and Delaune, 2008). Other authors have offered general methods and techniques for restoring freshwater and tidal wetlands (e.g., Davis and Ogden, 1994; Zedler, 2001), notably the construction of treatment wetlands to both ame­ liorate eutrophic conditions and optimize habitat and ecological services (e.g., Kadlec and Knight, 1996). In this chapter, we draw information from multiple sources and experiences to compile a series of case studies to focus our attention on characterizing the direct and indirect causes of wet­ land degradation and loss, particularly in coastal regions. We first discuss wetland global loss trends and major human impacts underlying causes and observed effects. We then use this scheme to identify differences and communalities in the processes regulating wetland loss in various types of wetlands. Here, we characterize wetland types based on specific geomor­ phologic settings and in the context of space availability and regional economic priorities. We decided to focus our case stu­ dies on ecosystems in which we have worked over the last 15 years, knowing that these specific examples represent only a fraction of the type of wetlands distributed around the world. We feel that by using specific examples to identify general causes hampering the protection and restoration of wetlands (and where relatively large data sets are available), identification of causes and effect is facilitated to draw general conclusions on larger scales. We hope that this perspective will provide useful information to help underline the future of wetland conserva­ tion in the context of local social and cultural perceptions while also acknowledging economic realities. The examples used in this chapter include deltaic regions (Mississippi River Delta, Louisiana, the USA; Grijalva– Mezcalapa–Usumacinta (GMU), Mexico; and Central Coast, the Netherlands), islands (Puerto Rico), and karstic platforms (Everglades, FL, USA). These case studies not only represent a range of environmental settings but also show a variety of human interventions that have played a major role in wetland gain and losses during the last 100 years, particularly at large scales (>100 km2); natural disturbances are also major 187 Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats features of each of these landscapes. By including the ecologi­ cal role of these large­scale disturbances, we plan to frame the problem of wetland loss in the context of global climate change and sea­level rise. Thus, our main objective in this chapter is to underline general patterns to help discuss alter­ natives and approaches for the development of wetland conservation programs in a century where financial and nat­ ural resources (space and water) will be increasingly limited (e.g., Day et al., 2009). 8.07.1.1 Current Wetland Global Extent and Loss Current estimates of global wetland area range from 6.8 to 10.1 million km2. Mitsch and Gosselink (2007) analyzed published estimates and concluded that the world’s wetland area is between 7 and 10 million km2 (Lehner and Döll, 2004) (Table 1). This area represents 5–8% of the Earth’s land surface where 56% of this total wetland is found in tropical (2.6 million km2) and subtropical (2.1 million km2) regions (Figure 1). Additionally, sub­boreal (i.e., temperate), boreal, and polar areas occupy 1 million, 2.6 million, and 0.2 million km2, respectively (Maltby and Turner, 1983) (Figure 1). These numbers are based on a diverse range of wetland definitions and are thus considered an approximation because, depending on the criteria, they tend to include a large variety of ecosystems (e.g., rice paddies, shallow coastal areas, and large lakes). As a result of this variability in wetland inventory (from 5.3 to 12.8 million km2; Matthews and Fung, 1987; Darras et al., 1998; Finlayson and Davidson, 1999), net wetland loss at a global scale is also an overall estimate. However, despite the uncertainties in the total inventory of wetland area, there is no question that wetland area is being lost at rapid rates particularly in developing countries; for example, it is estimated that 50 000 km2 (25%) of mangrove wetlands, one of the most productive wetlands in coastal sub­ tropical and tropical regions (Twilley, 1998; Alongi, 2008), Global wetland area (�106 km2) comparison by climatic zone Table 1 Zone Maltby and Turner (1983) Matthews and Fung (1987) Gorham (1991) Finlayson and Davidson (1999) Ramsar Convention Secretariat (2004) Lehner and Doll (2004) Polar/boreal Temperate Subtropical/tropical Rice paddies 2.8 1.0 4.8 (-) 2.7 0.7 1.9 1.5 3.5 (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) 1.3 (-) (-) (-) (-) Total wetland area 8.6 6.8 (-) 12.8 7.2 8.2–10.1 (-) no estimation. Modified from Mitsch, W.J., Gosselink, J.G., 2007. Wetlands, Fourth ed. Wiley, New York, NY. 0 300 600 900 90 3 2 Area (10 km ) 60 2 Area (103 km ) Latitude [deg] Lake Reservoir River Freshwater marsh, floodplain Swamp forest, flooded forest Coastal wetland pan, brackish/saline wetland Bog, fen, mire Intermittent wetland/lake 50–100% wetland 25–50% wetland Wetland complex (0–25% wetland) 30 0 –30 –60 400 Gross wetlands map GLWD 300 Stillwell-Soler et al. Mathews and Fung Cogley Wetland of GLCC Wetland of MODIS 200 100 –180 –150 –120 –90 –60 –30 0 30 60 90 120 150 180 Longitude [deg] Figure 1 Global wetland world spatial distribution and area. General extent is a composite from a number of sources. For details in calculation and wetland databases (GLWD) see Matthews and Fung (1987) and Lehner and Döll (2004). From Lehner, B., Döll, P., (2004). Development and validation of a global database of lakes, reservoirs and wetlands. Journal of Hydrology 296, 1–22. 188 Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats have been lost since 1980 (FAO, 2003). The most extensive area of mangroves is located in Asia, followed by Africa and South America (Table 2). Four countries (Indonesia, Brazil, Nigeria, and Australia) account for about 41% of all man­ groves, and 60% of the total mangrove area is found in just 10 countries (Figure 2). Negative annual changes in percentage are 1.9% and 1.1% for the period 1980–90 and 1990–2000, respectively (FAO, 2003). These values are similar to other estimates for the entire period 1980–2001 (2.1%) (Valiela et al., 2001). Loss of approximately 50% of wetlands around the world indicates the significant effect of human activities; for example, one of the best­documented wetland losses (53%) is registered in the continental US after European settlement (Mitsch and Gosselink, 2007). The major causes of wetland loss include drainage and hydrologic modifications with dikes, dams, and levees. These impacts are having major effects in Europe, Asia, and Africa where up to 65%, 27%, and 2%, respectively, of wetland area have been lost to agriculture and silviculture practices (Dahl, 2000; Ramsar Convention Secretariat, 2004, Dahl, 2006). Examples of countries where wetland loss is more Table 2 than 65% include Spain, Lithuania, Sweden, and China (Lu, 1995; Revenga et al., 2000). 8.07.1.2 Human Impacts on Wetland Area The causes leading to wetland loss and degradation are well recognized. Given the increasing global impact of human actions on natural ecosystems, there are several reviews identi­ fying the relative contribution of human actions to wetland loss. For example, Mitsch and Gosselink (2007), using infor­ mation compiled by Dugan (1993), partitioned direct and indirect human actions contributing to wetland loss and com­ pared them to natural events triggering wetland degradation and loss (Table 3). Flooding, hydrology, hydrach soils, and water­tolerant plants ecologically characterize wetlands (Reddy and Delaune, 2008); thus, human impacts negatively altering one or several interactions among these variables can contribute to wetland loss. Indeed, because over 70% of the world population lives in or near coastal regions, coastal wet­ lands have been one of the most affected types of wetlands (Hopkinson et al., 2008). Global status and trends in mangrove area extent by geographic region Most recent reliable estimate 1980 Region Reference Area (103 ha) year Area Area Area (103 ha) (103 ha) (103 ha) % change Area Area % (103 ha) (103 ha) Change Africa Asia Oceania North and Central America South America 3390 6662 1578 2103 2030 1993 1991 1995 1994 1992 3659 7857 1850 2641 3802 3470 6689 1704 2296 2202 −19 −117 −15 −34 −160 −0.5 −1.6 −0.8 −1.4 −5.3 3351 5833 1527 1968 1974 −12 −86 −18 −33 −23 −0.3 −1.4 −1.1 −1.5 −1.1 World total 15763 1992 19809 16361 −345 −1.9 14653 −171 −1.1 1990 Annual change 1980–90 2000 Annual change 1990–2000 From Wilkie and Fortuna (2003). Mangrove extent (ha) 1–100 100–1000 1000 –10 000 10 000–100 000 100 000–500 000 500 000–1000 000 1000 000–2 000 000 2000 000–6 000 000 no mangroves Figure 2 World mangrove occurrence and overall extent per country. From Wilkie, M. L., Fortuna, S., 2003. Status and trends in mangrove area extent worldwide. Forest Resources Assessment Working Paper No. 63. Forest Resources Division. FAO, Rome. 189 Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats Table 3 Different levels of human activitity causing wetland loss and degradation Freshwater marshes Lakes/ littoral zone Peatlands Swamp forest XX X XX X XX XX X XX X X X XX X XX XX XX XX XX XX XX XX XX XX X X X X X X XX X Cause Estuaries Floodplains Direct • Agriculture, forestry, mosquito control drainage • Stream channeliziation and dredging; flood control • Filling–Solid–waste disposal; roads; development • Conversion to aquaculture/mariculture • Dikes, dams, seawall, levee construction • Water pollution–urban and agricultural • Mining of wetlands of peat and other materials • Groundwater withdrawl XX X XX XX XX XX X XX Indirect • Sediment retention by dams and other structures • Hydrologic alteration by roads, canals, etc. • Land subsidence due to groundwater, resource extraction, and river alternations XX XX XX Natural events • Subsidence • Sea-level rise • Drought • Hurricanes, tsunamis, and other storms • Erosion • Biotic effects X XX XX XX XX XX X XX XX XX XX X X X XX XX XX XX indicates the common and important cause of wetland loss and degradation; X indicates present but not a major cause of wetland loss and degradation; and blank indicates that the effect is generally not present except in certain situations. Modified from Mitsch and Grosslink based on Dugan (1993) data. Practices such as excessive harvesting, hydrological mod­ ifications and seawall constructions, costal development, and pollution are some of the most pressing causes of costal wetland loss. Similarly, inland wetlands have been impacted by stream channelization, agriculture, forestry, stream canalization, aquaculture, mining, water pollution, groundwater withdrawal, and urban development. Indirect modifications of river sediment patterns, hydrologic altera­ tions, highway construction, and land subsidence (e.g., as a result of groundwater extraction and river alterations) are indirect causes of wetland loss. Among the most critical natural events causing wetland reduction are subsidence, sea­level rise, droughts, storms, erosion, and biotic effects (e.g., exotic species invasion). In general, it is the interac­ tion between human and natural drivers that exacerbates wetland loss, particularly in coastal areas where hurricanes and major hydrological modifications interact with tremendous negative economical and social impacts (Costanza et al., 2006). Figure 3 shows how an increase or decrease in water level, nutrient status, and natural Natural wetland Increased Flooding impeding natural drainage Water level Decreased Drainage Eutrophication; siltation Nutrients Flood control leading to reduced spring siltation Burning; reservoir construction; off-road vehicles Disturbance Fire suppression; flood control; water-level stabilization Figure 3 Human-induced impact on wetlands, including effects on water level, nutrient status, and natural disturbance; by either increasing or decreasing any one of these factors, wetlands can be altered. Modified from Mitsch, W.J., Gosselink, J.G., 2007. Wetlands, Fourth ed. Wiley, New York, NY. and Keddy, P.A., 1983. Freshwater wetland human-induced changes: indirect effects must also be considered. Environmental Management 7, 299–302. 190 Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats disturbance can have different outcomes in wetland ecosys­ tems health. Any alteration of these factors, as a result of human activity, can directly or indirectly lead to wetland alteration (Keddy, 1983). 8.07.2 Restoration and Rehabilitation: Why Semantics Matter When Addressing Loss of Area and Habitat in Wetland Ecosystems In terms of wetland management and restoration, physical space is becoming an increasingly critical limiting resource. To understand the processes leading to the loss of space, area, and habitats where wetlands develop, we need to identify the intended and unintended consequences of human impacts, particularly in the context of natural disturbances, which can exacerbate negative effects on the sustainability of natural eco­ systems. Paradoxically, entire ecosystems have evolved and developed by assimilating the effects of major climatic distur­ bances (e.g., hurricanes), which can regulate ecological functions at large temporal and spatial scales (Hopkinson et al., 2008; Lugo, 2008). Yet, ecosystems, including wetlands, are subjected to major stresses as a result of human impacts at smaller spatial and temporal scales than those of many natural disturbances (decades, <30 km2). A primary difference in these two types of disturbances is the persistent nature and accumu­ lative effect of human disturbances not typically seen with natural disturbances. It is the long­lived, chronic stresses that strongly impede an ecosystem’s capability to ‘rebound’ (resi­ lience) to an average ‘steady­state’ condition. It is clear that human activities can easily trespass on ecological thresholds, leading to the degradation, and, in extreme cases, collapse, of entire ecosystems and societies (Diamond, 2005). Wetland loss is a prime example of this downward trend around the world, elapsing over a relatively short period (<150 years, since the Industrial Revolution). As a result of increasing wetland loss around the world, wetland protection and restoration programs have been created in an effort to maintain and recuperate lost wetland acreage and ameliorate additional habitat reduction resulting from human actions (Day et al., 2005, 2007; Mitsch and Day, 2006). The Ramsar Convention on Wetlands is one of the most comprehensive international organizations strongly pro­ moting the conservation of wetland habitats. The main goal of this organization is to implement the Convention on Wetlands of International Importance treaty, which was signed by 18 nations in 1971 (Fraser and Keddy, 2005). The Ramsar Convention had grown to encompass 114 nations, and includes more than 1000 sites covering approximately 0.7 million km2 (Frazier, 1999). The countries with the most Ramsar area include Canada, the Russian Federation, Australia, and Denmark (Table 4). In an attempt to protect wetland areas before they are degraded or lost, restoration of already degraded wetlands has become a critical management strategy. Indeed, restora­ tion ecology is now considered a framework to recover altered structural and functional ecosystem properties. Yet, restoration ecology is a relatively unfledged science with an evolving conceptual framework where specific principles are being developed from empirical experiences. One of the major issues when assessing how successful a project Table 4 Countries (top 10) with the most Ramsar sites and largest cumulative areas or Ramsar sites Countries Numbert of sites Total area (hectares) With most Ramsar sites United Kingdom Australia Italy Ireland Denmark Spain Canada Russian Federation Germany Sweden 119 49 46 45 38 38 36 35 31 30 513 585 5 099 180 56 950 66 994 2 283 013 158 216 13 050 975 10 323 767 672 852 382 750 With most Ramsar area Canada Russian Federation Botswana Australia Brazil Peru Denmark Islamic Republic of Iran Mauritania United States 36 35 1 49 5 7 38 18 2 17 13 050 975 10 323 767 6 864 000 5 099 180 4 536 623 2 932 059 2 283 013 1 357 150 1 188 600 1 172 633 Modified from Fraser, L.H., Keddy, P.A., 2005. The World’s Largest Wetlands. Cambridge University Press, Cambridge. can be in reversing ecological damage is the definition of restoration objectives and respective performance measures (Twilley and Rivera­Monroy, 2005). The challenge is assess­ ing when the structural or functional property has been reinstated and forecasting the timescale of occurrence. However, this is not an easy task because we frequently do not have long­term measures of ecosystem properties, making it difficult to determine when the system has reverted to predisturbance conditions. In addition, both local and global effects of human actions, which are becoming increasingly critical in controlling ecosystem function, are influencing ecosystems. For example, wetland ecosystems, particularly in coastal environments, are now susceptible to accelerating sea­level rise in combination with changes in temperature. This, in combination with changes in land use in the upland areas, results in a ‘coastal squeeze’ (Nicholls and Mimura, 1998), especially where not enough physical space remains for natural sys­ tems to migrate inland (particularly under rising sea level), significantly compounding area losses. There is a consensus that ecological theory should be incor­ porated in wetland creation and restoration to improve management efforts (i.e., ‘the acid test of ecological under­ standing’) (Bradshaw, 1997; Parker and Pickett, 1997; Zedler, 1999a, 1999b). Ecological theories and concepts (e.g., niche, disturbance, plant succession, scales and hierarchy, and com­ petition) are now being tested using restoration projects not only to advance such theories but also to test hypotheses about specific processes related to changes in biogeochemistry cycling or carbon storage (e.g., Zedler and West, 2008; Twilley and Rivera­Monroy, 2009). However, one of the problems still Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats apparent in the literature is the actual definition of ‘restoration’ and ‘rehabilitation.’ In some cases, these concepts are used interchangeably, making it difficult to evaluate whether a par­ ticular ‘restoration’ project has been successful, and if the observed trends are sustainable in the long term. This is partic­ ularly important in the context of large spatial­scale, regional management projects. Restoration has been defined as “to bring back to the original state…or to a healthy or vigorous state,” whereas rehabilitation has been defined as “the action of restoring a thing to a previous condition or status.” Although similar to the restoration concept, Bradshaw (1997) stressed, “something that has been rehabilitated is not expected to be in a original or healthy a state as if it had been restored (Francis et al. 1979)” Thus, the concept can be used to indicate “any act of improvement from a degraded state” (Wali, 1992). Similarly, Field (1999) proposed that rehabilitation of an eco­ system is the act of “partially, or more rarely, fully replacing structural or functional characteristics of an ecosystem that have been diminished or lost, or the substitution of alternative qualities or characteristics than those originally present with provision that they have more social, economic or ecological value than existed in the disturbed or degraded state.” On the other hand, restoration of an ecosystem is “the act of bringing an ecosystem back to, as nearly as possible, its original condi­ tion.” In this conceptual framework, restoration is seen as a special case of rehabilitation. Field (1999) pointed out that “land use managers are concerned primarily with rehabilitation and are not much concerned with ecological restoration. This is because they require the flexibility to respond to immediate pressures and are wary of being obsessed with recapturing the past.” Moreover, Streever (1999), based on a review of a variety of ‘rehabilitation’ projects in developing nations defined reha­ bilitation as “an umbrella term that includes both ‘restoration’ 191 and ‘creation,’ where restoration is the return of a system to some previous condition, and creation is the establishment of a wetland where no wetland had existed in the past.” In light of these definitions, one can readily identify the problem of developing criteria to evaluate the success of ‘restoration’ projects. As restoration is the return of a system to a previous condition, according to the definitions listed above, how realistic is this goal in the context of increasing human impacts including global change? This is particularly difficult when we consider large­scale restoration projects in which cost and social expectations are often disconnected from the natural trajectory of ecosystem change as a result of human intervention. In most restoration projects, societal expectations are in disconnect with the degree of knowledge about the target ecosystem. It is not rare to find cases in which expectations from restoration and rehabilitation projects are contradictory when trying to balance two ecosystem functions, for example, wetland restoration in the context of storm surge protection (Costanza et al., 2006, 2008). In most situations, despite the extension of the wetland restoration/rehabilitation effort, it is clear that the degree in which ecosystem theory is applied to these projects is highly variable, thus variably affecting out­ comes. In the next section, we focus on a number of these issues in the form of five case studies from around the world. Van Cleve et al. (2006) reviewed several large regional­scale restoration projects to evaluate the influence of natural science in coastal restoration (Figure 4). They analyzed how restora­ tion efforts integrate science into the organizational structure and assess if adequate organization would dictate the effective use of science. The restoration efforts included in this study are among the largest in the world and consist of Chesapeake Bay Program (166 000 km2), Kissimmee River Restoration Project (104 km2), Comprehensive Everglades Restoration Program 50 40 Bay-Delta Effective use of science Glen Canyon 30 Everglades Skjern Louisiana Chesapeake Kissimmee Salisbury 20 Rhine 10 European programs US programs 0 0 10 20 30 40 50 Effective science Figure 4 Relative importance of effective science (ES) vs. effective use of science (EU) of large-scale restoration programs in Europe and USA. The straight line is drawn to show equally balanced ES and EU. If programs score better in ES relative to EU, they fall below and to the right of the diagonal line. If programs score better in EU relative to ES, they fall above and to the left of the diagonal line. From Van Cleve, F.B., Leschine, T., Klinger, T., Simenstad, C., 2006. An evaluation of the influence of natural science in regional-scale restoration projects. Environmental Management 37, 367–379. 192 Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats (47 000 km2), California Bay­Delta Program (3000 km2), Glen Canyon Dam Adaptive Management Program (length: 473 km), Louisiana Coastal Area Study (38 000 km2), International Commission for the Protection of the Rhine (185 000 km2), Skjern River Restoration Project (22 km2), and the Salisbury Plain LIFE project (197 km2). Using techniques of program evaluation to analyze the use of natural science, Van Cleve et al. (2006) found that the use of science can be con­ strained by the absence of formal, integrated mechanisms for including science into program execution. One of their major findings is the different perception of the word ‘restoration’ in Europe where returning a system to a ‘pristine’ condition is considered neither possible nor desirable. Another finding, after ranking categorical information about project perfor­ mance, is that most projects accumulate science as they develop and age; however, this critical information is not necessarily used to increase effectiveness in later implementa­ tion stages. After ranking different criteria related to achieving program objectives and using categorical criteria for scoring a list of project attributes to define scores of ‘effective science’ (e.g., peer review, monitoring, and conceptual models) and ‘effective use of science’ (e.g., defined science team, use of science in goal setting, and identifiable science leadership) (Figure 4), this study indicates that the utilization and influ­ ence of science within those restoration programs are “variable, context dependent, and (in most cases) still suboptimal.” This finding is not surprising, given the large complications in inte­ grating natural science in the social and economic decisions (Sklar et al., 2005) (see Section 8.07.4). For example, conflicts and inconsistencies among statutory responsibilities, court orders, agency missions, and stakeholder preferences can con­ found the application of many adaptive management actions (Walker, 2005). Of particular significance is the case of coastal Louisiana, which ranks last in the analysis described above. Although several federal and state partnerships exist, there is no ‘formal science team’ as in the case of the Comprehensive Everglades Restoration Plan (CERP) in the Florida Everglades restoration effort (Chimney and Goforth, 2001; Sklar et al., 2005; Chimney and Goforth, 2006). Although a National Technical Review Committee advises a ‘delivery team’ and provides independent peer review, there still exists a major disconnect for the transfer of scientific findings to restoration programs (Costanza et al., 2006; Day et al., 2007) (see below). Moreover, given the major alterations in geomorphic and hydrological regimes (Hudson et al., 2008), it is increa­ singly difficult to determine if an intensely regulated and dynamic coastal region such as the Mississippi River Delta could actually be ‘restored’ to a previous state. The use of the term ‘restoration’ in the program titles listed above does reflect societal expectations. Are they realistic, particularly when we consider project cost of scaling up large temporal and spatial restoration and rehabilitation programs? Our recommendation is to use the term ‘rehabilitation’ more often to indicate the political and economic difficulties we face in conserving and managing wetland ecosystems. Although we use the term restoration throughout the rest of the text, we wanted to stress the need to use the correct operational terms when discussing the reaction to habitat losses as a result of human actions in coastal regions. 8.07.3 Case Studies 8.07.3.1 Mississippi River Delta, Louisiana, USA The Mississippi River deltaic plain (i.e., coastal Louisiana) was created over the past several thousand years by a series of delta lobes associated with rapid switching of the lower Mississippi River and its distributaries. The river switched courses across coastal Louisiana resulting in sediment deposits approximately 300 km wide and nearly 100 km inland. This marked the for­ mation of a vast deltaic plain and represented a time of progradation across the Louisiana coastline (Figures 5 and 6). The Louisiana deltaic plain is comprised of complex and highly dynamic ecosystems. The diversity of coastal habitats and land­ forms includes natural levees and ridges; forested wetlands; fresh, brackish, and saline marshes; and barrier islands. These unique habitats are hydrologically connected to one another and to the Gulf of Mexico. These coastal ecosystems support migratory routes for waterfowl, neo­tropical songbirds, various fish species, and commercially important shellfish including white shrimp, brown shrimp, blue crabs, and oysters. Alongshore transport of sediments generally occurs from east to west, and inshore sediment is distributed during high water events. Rapid wetland loss is a chronic problem across coastal Louisiana, and primarily within the Mississippi River deltaic plain (Figure 7). This is attributed to a combination of natural processes and human activities. Deterioration of Louisiana coastal wetlands began in the early nineteenth century at approximately the same period that the Mississippi River was leveed. Submergence resulting from subsidence is the major factor contributing to wetland loss in coastal Louisiana, and subsidence combined with sea­ level rise exceeds sediment accretion in many coastal areas with the greatest net subsidence occurring in the deltaic plain. Adequate sediment input is necessary for maintaining marsh surface elevation in response to increasing water level. During the last several decades, sediment load has decreased dramatically as a result of upstream land manage­ ment and by forcing the river down its present channel. This has deprived wetlands and coastal areas of mineral sediment critical to plant productivity and deltaic expan­ sion. Maintaining the Mississippi River in its present channel halted the delta switching process, causing sedi­ ment to be deposited into deep water off the continental shelf, and essentially cut off freshwater, sediment, and nutrient supply to Louisiana’s coastal landscape. The com­ paction of existing sediment, the absence of new sediment inputs, and the resultant submergence and saltwater intru­ sion contribute to the wetland loss. The relative rates of vertical marsh accretion and submer­ gence determine the long­term stability of Louisiana coastal marshes. Coastal marshes are highly susceptible to submer­ gence associated with a rise in relative sea level (Penland and Ramsey, 1990). Since the 1930s, it is estimated that 4921 km2 of land has been lost in coastal Louisiana with the majority of the loss in the Mississippi River deltaic plain region (Dunbar et al., 1992; Barras et al., 1994; Barras et al., 2003). Even though loss rates exceeded 104 km2 yr−1, primarily from the 1950s through the 1970s, current wetland loss estimates are lower. Between 1990 and 2000, wetland loss rates were estimated to be 61.2 km2 yr−1 (Figure 7). Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats 193 Figure 5 The deltaic plain landmass was built by a sequence of overlapping deltaic lobes that developed during the last 5000 years. From Day, J.W., Boesch, D.F., Clairain, E.J., Kemp, G.P., Laska, S.B., Mitsch, W.J., Orth, K., Mashriqui, H., Reed, D.J., Shabman, L., Simenstad, C.A., Streever, B.J., Twilley, R.R., Watson, C., Wells, J.T., Whigham, D.F., 2007. Restoration of the Mississippi Delta: lessons from Hurricanes Katrina and Rita. Science 315, 1679–1684. Although riverine sediment deposits are lacking, studies of Louisiana deltaic marshes have shown that most marsh areas, for a period of time, can vertically accrete and keep pace with subsidence, although there is an overall marsh deterioration. In sediment­deficient environments, such as in coastal Louisiana, accretion is strongly dependent on sequestration of significant amounts of organic matter (DeLaune and Pezeshki, 2002; DeLaune et al., 2003; Nyman et al., 2006). Soil organic matter accumulates from in situ marsh plant production (autochthonous), rather than from transport into the marsh from other areas (allochthonous). Therefore, factors which regulate plant growth, such as salinity and sub­ mergence, will directly affect soil organic matter accumulation and marsh stability. 8.07.3.1.1 Hurricane effects on coastal wetland loss Coastal wetland loss in Louisiana has also been impacted episodically by severe storm events. Storm surge resulting from hurricanes can scour and redeposit sediment and rooted marsh vegetation. Saltwater, pushed inland by storm surge and extreme tides, can also negatively affect certain marsh vegeta­ tion communities. Evidence suggests that global warming may increase storm frequency and intensity; for example, over the last century, sea­surface temperature in the tropics has increased by 1 °C and an associated increase in hurricane intensity has been noted (Emanuel, 2005). Hoyos et al. (2006) reported that the increase in the number of category 4 and 5 hurricanes during the 1970–2004 period was linked to the increase in surface­water temperature. If this scenario continues, Louisiana coastal marshes are likely to be impacted by major hurricanes on a more frequent basis in the future. Such an increase would likely have an impact on soil carbon storage in northern Gulf of Mexico marshes. In coastal Louisiana, it has been estimated that the combined effect of the 2005 hurricanes, Katrina and Rita, resulted in a loss of over 518 km2 of coastal marsh (Barras, 2006). A significant portion of this loss occurred in the Mississippi River deltaic plain. 8.07.3.1.2 Influence of coastal restoration efforts on reducing wetland loss The Coast 2050 Plan (Wetlands and Authority, 1998) was one of the first coordinated strategies for restoring Louisiana’s rapidly deteriorating coastal wetlands. The Coast 2050 Plan was developed in partnership with the public, parish govern­ ments, and state and federal agencies, and it was based on technically sound strategies designed to sustain coastal resources. The plan served as an overall template to provide program­neutral guidance for the development and implemen­ tation of coastal restoration projects. The restoration plan includes diverting Mississippi River water into Louisiana coastal wetlands. The introduction of nutrient­laden river water can significantly increase plant productivity and soil organic carbon accumulation. River diversions also decrease inland salinity and thus reduce stress on the coastal vegetation, slowing the rate of wetland loss (Figure 8). The actual amount of marsh preserved by coastal restoration is difficult to estimate. One estimate (Barras et al., 2003) projected a loss of 1295 km2 or 26 km2 yr−1 over the next 50 years based on current restora­ tion effort; however, this represents pre­Katrina and Rita estimates (Wetlands and Authority, 1998; Barras et al., 2003). Following Hurricanes Katrina and Rita, Visser et al. (2008) used the Coastal Louisiana Ecosystem Assessment and Restoration (CLEAR) Landscape Change model to assess the potential land gain resulting from restoration projects pro­ posed by the Louisiana Coastal Protection and Restoration Authority – Comprehensive Master Plan for a Sustainable 194 Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats Figure 6 On a global scale, river deltas and other coastal wetlands have faced a myriad of natural and human pressures. Many of these fragile ecosystems have been substantially altered, such that their current structure and function differ significantly from their historical, unaltered state. Examples of coastal areas experiencing major disturbances in different spatial and temporal scales include the Mississippi River Delta (USA), the Florida Everglades Ecosystem (USA), The Netherlands central coast, the Southern coastal region of Puerto Rico, and the Grijalva–Usumacinta Delta System (Mexico). Causes of loss of space and fragmentation are explained in the text. Color corresponds to geographical location on global map. Coast. Many of the restoration projects proposed by this group were more ambitious than those proposed under Coast 2050, and therefore model estimates showed higher levels of wetland area gained through these restoration projects. Over the course of a 50­year simulation (assuming historical land loss rates remained unchanged), the Master Plan restoration scenario resulted in an overall wetland loss of 619 km2 (5% of current wetland area), while 2368 km2 (18% of current wetland area) of wetlands were simulated as being converted to open water under the no action (no increased restoration) scenario. According to the 2007 CLEAR Landscape Change module out­ put, the Master Plan restoration scenario prevents the loss of 1749 km2 of wetland over a 50­year span (35 km2 yr−1) across coastal Louisiana when compared to the same time frame given the scenario of no increased restorative action. This translates into a 13% reduction in total wetland area loss over the course of 50 years. The spatial and temporal dynamics of wetland area created by Mississippi River diversions versus wetland area created by direct wetland and barrier island creation projects was also included in this estimate. Fifty years fol­ lowing restoration, 598 km2 of wetlands would be created by diversion processes, and 540 km2 by marsh and barrier island creation projects. Wetland creation from diversions is a gradual and steady increase over time, whereas marsh and barrier island creation projects result in a nearly ‘instant’ addition of wetland area. Both of these restoration scenarios (Visser et al., 2008) are best­case scenario estimates. The success of coastal restoration is also contingent on funding for completing and maintaining the restoration projects. Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats 195 (a) Land Loss 1932 to 2000 Land Gain 1932 to 2000 Projected Land Loss 2000 to 2050 Projected Land Gain 2000 to 2050 Backdrop Fall 1999 Landsat Thematic Mapper Satellite Images Primary Road LCA Subprovince Boundary –10 (b) N 0 10 20 30 40 Miles 20 000 18 000 Wetland areas (km3) 16 000 3 km2 yr –1 Net wetland gain 14 000 65 km2 yr –1 Net wetland loss 12 000 10 000 8000 6000 4000 2000 0 –7000 –6000 –5000 –4000 –3000 –2000 Years before present –1000 0 1000 Figure 7 (a) Historical and projected coastal Louisiana land changes: 1932–2050 (from Barras et al. 2003. USGS Open File Report 03-334, 39p.). (b) Wetland gain and loss over the last 6000 years; there has been a net loss of 65 km2 yr−1 since the last 100 years. (a) From Barras, J.A., Beville, S., Britsch, D., Hartley, S., Hawes, S., Johnston, J., Kemp, P., Kinler, Q., Martucci, A., Porthouse, J., Reed, D., Roy, K., Sapkota, S., Suhayda, J., 2003. Historical and projected coastal Louisiana land changes: 1978–2050. USGS Open File Report No. 03-334. USGS, Baton Rouge, LA. (b) From Costanza, R., Mitsch, W.J., Day, J.W., 2006. A new vision for New Orleans and the Mississippi delta: applying ecological economics and ecological engineering. Frontiers in Ecology and the Environment 4, 465–472. This examination, however, does show that restoration is critically important for slowing the rate of loss of Louisiana’s subsiding coastal environment (Figure 9). 8.07.3.1.3 Human impact Louisiana’s coastal wetlands, including the Mississippi River deltaic plain, are also the center of a culturally diverse society that relies heavily on the utilization of these resources. Oil and gas activities, navigation, levees, agriculture, and urban and other land uses have disrupted the natural hydrologic and sediment transport processes. For example, following the Great Flood of 1927, the world’s longest system of levees was constructed by the US Army Corps of Engineers (COE) under the Flood Control Act of 1928. By 1931, the Mississippi River had 29 locks and dams, hundreds of runoff channels, and thousands of kilometers of levees. Over the years, con­ siderable resources have been expended in maintaining and upgrading the levee’s systems. 196 Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats Figure 8 Tradeoffs associated with delta plain restorative hydrology and river diversion scenarios; see text for further explanation. From Enhancing Landscape Integrity in Coastal Louisiana: Water, Sediment and Ecosystems CLEAR 2006 (http://www.clear.lsu.edu/). Figure 9 Future of coastal Louisiana with aggressive restoration: a sustainable coast. From Restore vs. Retreat: Securing Ecosystem Services Provided by Coastal Louisiana (CLEAR 2007; http://www.clear.lsu.edu/). Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats Due to restrictions from storm and flood protection levees and human development, there is little area for upland migra­ tion of coastal marsh in response to increases in water levels in coastal Louisiana. As a result, most coastal marshes are being replaced by shallow open water area as sea levels continue to rise. Humans have also converted sustainable wetlands into pastures, agricultural lands, and cities, which now require higher levees and larger pumps for flood protection. Traditionally designed levees disrupt the delivery of sediments, and pumping of water from the soil to maintain dry land within levees reduces soil accretion and requires increasing both the levee height and the pump capacity as the land con­ tinues to sink and the sea level continues to rise. Before the levees were built, regular flooding from rivers and bays added sediments, and healthy wetland plants added organic matter. This caused the elevation of the land to remain stable relative to sea­level rise and soil subsidence. The wetlands have also his­ torically processed and removed nutrients from the river water. Elevated nutrient concentrations in the Mississippi River have resulted in the development of a hypoxic zone in the northern Gulf of Mexico. Although designing and implementing large­scale, long­ term coastal restoration projects are a highly complex endea­ vor, there are many examples in which the cause of wetland loss and the restoration strategy needed to restore the wetlands are clearly understood and documented. However, the 95 °0’0”W 94 °0’0”W 197 political, economic, and social arenas often limit full restora­ tion initiatives. For example, several fundamental principles needed to restore coastal ecosystems in Louisiana are at odds with the fundamental principles needed to design traditional flood protection levees (i.e., hydrologic connectivity is vital for sustaining coastal wetlands, whereas traditional flood protec­ tion levees serve to sever hydrologic connectivity). In an attempt to sustain both the human and natural systems, we propose expanding assessments of innovative flood protection technologies, such as ‘leaky levees, ‘smart levees’, and the multiple lines of defense strategies to help balance the dynamic principles needed to both restore and protect the dynamic systems in the Mississippi River Deltaic Plain. 8.07.3.2 GMU Delta Region, Tabasco–Campeche, Mexico The GMU Delta (20 000 km2) is the second largest deltaic system in the Gulf of Mexico after the Mississippi River Delta. Like most deltaic regions, the GMU region is influenced by eustatic sea­level rise, which controls geomorphic and ecologi­ cal processes. Freshwater discharge in this deltaic complex is 87 million m3 yr−1, influencing extensive wetlands and coastal floodplains; this volume of water represents �30% of Mexico’s total freshwater discharge into adjacent coastal waters (Ortiz­ Perez and Benitez, 1996). The lower GMU delta is located in the Mexican states of Tabasco and Campeche and includes 93 °0’0”W 92 °0’0”W 91 °0’0”W 20 °0’0”N Gulf of Mexico 19 °0’0”N Bay of Campeche Lagoons 1. Carmen 2. Machona 3. Mecoacan 4. Pom 5. Atasta 6. Terminos 4 5 San Pedro y San Pablo R. 3 2 R. Palizada R. Chillapa R. Usumacinta R. Tonala R. La Sierra R. Coatzacoalcos River Mezcalapa R. Republic of Guatemala 18 °0’0”N Gr ija lva 1 6 Figure 10 Grijalva–Mezcalapa–Usumacinta (GMU) Delta region, Tabasco–Campeche. This delta is the second largest deltaic system in the Gulf of Mexico and includes the largest Mexican rivers discharging into the Gulf of Mexico. The combined discharge of the Grijalva (length: 640 km) and Usumacinta (length: 1100 km) is 4402 m3 s−1. Terminos Lagoon is the largest coastal lagoon in Mexico (�1800 km2). Modified from Ortiz-Perez and Benitez, 1996. 198 Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats mangroves, freshwater marshes, submerged aquatic vegetation, and coastal water bodies, including Terminos Lagoon, the largest coastal lagoon in Mexico (�1800 km2) (Figure 10). Mangroves fringe lagoon shores, crowd into abandoned river channels, spread out across broad interdistributary basins, or are concentrated in narrow swales of low­lying ridges which are seasonally flooded by Gulf water. The climate is humid and tropical with mean annual temperatures greater than 25 ˚C and annual rainfall ranging from 1500 to 5000 mm. This climatic regime, along with large river discharge and low elevations, strongly influences hydrographic conditions where the tidal range is 30–50 cm, which controls mangrove forest extension and distribution (Thom, 1967). Rainfall during the Norte (cold fronts) season (October–March) reduces the temperature to 15–20 °C for several days (1–5 days). Thus, the periodic ‘norte’ storms of winter are reported to be more significant than infrequent hurricanes in influencing not only vegetation structure but also local climate conditions. 8.07.3.2.1 Hydrology and loss of space In the most recent hydrographic configuration of the GMU, river streams split and blend along the inundation floodplain, but it is only the Tonala River that remains well defined, dis­ charging directly into the Gulf of Mexico. Although other tributaries are active, the main discharge is through the Grijalva River (Figure 11). The combined discharge of the Grijalva (640 km) and Usumacinta (1100 km) is 4402 m3 s−1 (Hernandez­Santana, et al. 2008). In the past, the Mezcalapa River discharged in the Mecoacan Lagoon, as was the case of the Usumacinta River into the San Pedro–San Pablo River, which currently dries out during the dry season and becomes only active when excess water is captured in the lower Usumancinta River watershed. Similar to the other coastal regions discussed in this section, the environmental setting determines the success and vulnerability of human infrastructure and sustai­ nability of natural ecosystems. This region (in addition to other areas in the states of Veracruz, Campeche, and Quintana Roo) is currently the focus of national priorities to understand the causes leading to acute coastal regression and erosion in more than 15 000 km2 of coastline as a result of its vulnerability to sea­level rise (Hernandez­Santana et al., 2008). Although cur­ rent regression estimates range from 3.1 to 8.2 m yr−1, these values are much lower than those registered for the Louisiana coastal region (–36.8 m yr−1) (Morton et al., 2005). Mangroves along southern shores of lagoons indicate significant signs of wave erosion, particularly in the San Pedro–San Pablo river mouth. Areas in populated sites established in abandoned delta lobes have regressed more than 500 m affecting not only road and urban infrastructure (causing human migration) Hypothetical extent of the delta Gulf of Mexico r Beach Ridges System of Grijalva River ve of Ri m lo ste Pab y S n es Sa dg d Ri an ch edro a Be n P Sa Sa n Pe dr o an d Sa n Pa bl o Ri ve Usum acinta rs Rivers Beach Ridges System of Central Basin Terminos Lagoon 0 50 Km Usumacinta River Delta Mezcalapa River Delta Figure 11 Beach-Ridges spatial distribution along the old central delta and Usumacinta River and the current Grijalva River Delta, which has been increasingly impacted by human activities, although the degree of hydrological control by human actions is relatively lower than in the Mississippi coastal region. Modified from Ortiz-Perez and Benitez, 1996. Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats but also oil exploration and delivery infrastructure in the last 60 years (Hernandez­Santana et al., 2008). 8.07.3.2.2 Human Impacts As in the case of the Mississippi River delta region, the GMU delta has been gradually and increasingly impacted by human activities, although the degree of hydrological control by human actions is relatively lower than in the Mississippi River coastal region (Yanez­Arancibia and Day, 2004). For example, the river control structures in the Mississippi–Atchafalaya watershed directly manage freshwater discharge (Red River control structure: 30% Atchafalaya River, �70% Mississippi River) into the Gulf of Mexico to maintain navigational routes and avoid a natural shift of the delta, which is not the case in the GMU delta. There are actually five watersheds (Usumacinta, Mezcalapa, Chilapa, La Sierra, and Tonala) controlling the geomorphology of the delta downstream (Figure 12). Of the total Grijalva and Usumancinta River watershed area (186 000 km2), approximately 60% remains in a nearly natural state, although dams built in the Grijalva, and Mezcalapa rivers (e.g. Grijalva dams: Angostura, Chicoasén, Malpaso, Peñitas) to store water for power generation are increasingly modifying water availability along the main watershed (Figure 12). Thus, human pressure over water availability and quality is one of the major impacts on the natural processes regulating 199 sediment input and wetland productivity. The watersheds are located mainly in three Mexican states (Chiapas, Tabasco, and Campeche), and, as a result of the dams sediment input, is significantly reduced affecting delta formation and sustainabil­ ity. As previously noted for the Mississippi River Deltaic Plain, increasing erosion in the coastal region is compounded by natural subsidence and sea­level rise, which are exacerbating coastal regression, particularly in the mouth of the San Pedro– San Pablo River and the Atasta coastal area next to Terminos Lagoon. Yet, changes in sediment delivery have also increased sediment deposition in other areas (e.g., Palizada fluvial– lagoon–deltaic system), negatively impacting navigation and promoting major changes in wetland and terrestrial habitat structure and productivity. Road construction and urban development have been one of the major drivers in modifying hydrological patterns in the GMU and promoting the loss of physical space and habitats, and because several human settlements are located in low elevation zones, they are prone to frequent flooding events as a result of high precipitation in the upper watershed and increasing impacts by tropical storms and hurricanes, particu­ larly during the last decade. The flooding of Villahermosa city (population: 658 524) in 2007 showed the susceptibility of urban centers in the lower delta region, similar to the case of New Orleans following Hurricanes Katrina in 2005. Just as New Gulf of Mexico Hydrology Superficial flow Divide Rivers Terminos Lagoon 7 5 8 1 2 4 3 1. Tonala 2. Mezcalapa 3. La Sierra 4. Chilapa 5. Grijalva 6 6. Usumacinta 7. San Pedro and San Pablo 8. Palizada Dams A = Nezahualcoyotl B = Chicoasen C = La Angostura A Watersheds B C Vol.* (%) Usumacinta 59 52 Mezcalapa 27 23 Chilapa 13 11 La Sierra 7 6 Tonala 6 5 * Thousands of millions of m3 Gulf of Tehuantepec Figure 12 Watershed boundaries and main rivers discharging into the Tabasco and Campeche delta plains. The Usumacinta watershed contributes 52% of the total water volume registered for this coastal region (59 � 109 m3). Modified from Ortiz-Perez and Benitez, 1996. 200 Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats Orleans lies on the banks of the Mississippi River, and many parts of the city are more than 1m below sea level, Villahermosa was built on the banks of the Grijalva River. The average eleva­ tion of the city is 10 m above sea level, and it is surrounded by a interconnected system of lagoons (e.g., Illusions Lagoon), which exacerbates the vulnerability to major flooding; however, con­ trary to New Orleans, Villahermosa lacks the complex and technologically advanced system of gates and levees that largely protected (until 2005) the city of New Orleans. This discrepancy in the control of flooding in cities located in productive deltas underlines the economic and sociopolitical priorities and reali­ ties between developing and developed nations (see Sections 8.07.3.1 and 8.07.3.3). 8.07.3.2.3 Mangrove wetlands Major changes in the GMU natural landscape can be gauged by evaluating spatial changes in mangrove vegetation, which is one of the dominant coastal vegetations in the region. The dynamic ecology of mangroves and associated flora in the GMU delta is considered to reflect habitat change induced by continually changing, geomorphic processes (Thom, 1967). Thus, mangrove forests are very susceptible to changes in the hydroperiod and are good indicators of short­ and long­term modifications in hydrology. Recent estimates in mangrove area loss from 1995 (589 km2) to 2001 (483 km2) showed a net loss of �18%; regions with major losses are the San Pedro– Grijalva–Mecoacán and Carmen, Pajonal, Machona (CPM)– Rio Tonalá. This rate of loss exceeds the national average in Mexico (2.1%) and is close to losses of tropical forest of which only 2–4% of the original area remains upstream at higher elevations. It is estimated that at this rate of change, 39% of mangrove wetlands will be lost in 15 years (Hernandez­Trejo et al., unpublished data). In addition to hydrological modifica­ tions, other human activities have contributed to the reduction of mangrove area including agriculture, livestock farming, oil and gas exploitation and exploration infrastructure, fire, wood extraction, and carbon production. 8.07.3.2.4 GMU ecological and economic importance Because of the large wetland extension of this deltaic region, the GMU is considered one of the most critical coastal eco­ systems for the economic development not only for the States of Tabasco and Campeche but also for Mexico overall. This area is in the epicenter of extensive oil and gas production, which overall represents 40% the total revenue for Mexico (it is ranked ninth in world oil exports). For example, the Biosphere Reserve Pantanos del Centla (extension 3027 km2) is currently one of the most threatened wetlands in the central delta region; it comprises several natural habi­ tats that range from mangrove to brush, whereas pasture and oil extraction fields account for 18% of the total area (Reyes et al., 2004; Guerra­Martinez and Ochoa­Gaona, 2005, 2008). Unfortunately, there are major gaps in the under­ standing of the long­term effect of dam construction on hydrology and sediment transport along main rivers and the effect of high deforestation rates in the upper watersheds. Contrary to the relatively well­understood mechanisms of hypoxia development in coastal Louisiana (Justic et al., 2003; Scavia et al., 2003), as a result of the high loading rates of nitrogen, there are major unknowns regarding the effect of human activities on the water quality of the rivers, lagoons, and coastal waters across the GMU delta region and related watersheds (Ortiz­Perez and Benitez, 1996). Despite the well­recognized economic, ecological, and social impor­ tance of the GMU and associated wetlands, there is a lack of long­term environmental monitoring, which hinders the implementation of science­based management plans and restoration and rehabilitation programs. Recent efforts to identify the major environmental thresholds and linkages to human activities in the GMU and the resulting development of coastal management plans are encouraging. However, the implementation of actions to ameliorate environmental impacts is still limited by the availability of technical, scien­ tific, and economic resources. 8.07.3.3 8.07.3.3.1 The Netherlands History of wetlands in the Netherlands Approximately 10 000 km2 of the surface of the Netherlands is below sea level, including the area occupied by wetlands before human alteration (Figures 6 and 14). Uplands and wetlands in this area were formed with sediments from several rivers, the Rhine River being the largest contributor. Most of the region consisted of estuarine wetlands, whereas smaller areas along the central part of the coast were separated from marine influences by large continuous dune ridges and devel­ oped ombrotrophic raised bogs (Zagwijn (1986) cited in Wolff (1993)). Bogs also developed in the fresher areas influ­ enced by smaller rivers. The floodplain of the Rhine and Meuse Rivers was primarily occupied by swamp forest (Figure 13). Major human alterations to this coastal ecosystem started with the farming of freshwater bogs in the Middle Ages (Edelman (1974) cited in Wolff (1993)) (Figure 10). Drainage increased oxidation of the peat surface and the land subsided, which made these new agricultural areas more vul­ nerable to flooding by both riverine and marine waters (Wolff, 1993). In response, the population built dams and dikes to protect and maintain the ‘new land’. All rivers in the western Netherlands were flanked with dikes as early as AD 1150, while over the next two centuries, embankment moved eastward, toward the German border (Van Veen, 1962). As more land was converted in this way, water was confined to smaller flood plains, which raised water levels during storm surges and river floods. Inevitably, dikes failed, and the land flooded. Between the tenth and fourteenth centuries, several permanent lakes formed, or land was lost to the sea in �50% of the coastal reclamations (Wolff, 1993). Coastal marshes started growing on the edge of these lakes and naturally accreted, reclaiming part of the lost land. During the first half of the seventeenth century, the use of windmills as water pumps resulted in the reclamation of nearly 300 km2 of these lakes (Wolff, 1993) and 400 km2 of saline marsh (Van Veen, 1962). Peat extraction for fuel started expanding in the twelfth century, peaked in the nineteenth century, and continued well into the twentieth cen­ tury. This extraction resulted in the loss of over 1800 km2 of ombrotrophic perched bogs in the upland areas in the nor­ theastern Netherlands, with only 36 km2 of this wetland habitat remaining (Best et al., 1993). In the mid­twentieth century, fossil­fuel­based technolo­ gies enabled the impoundment and artificial drainage of 1680 km2 of a previously tidal brackish bay in the center of Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats 201 Dunes Salt marshes Saline lakes Freshwater lakes Fen mires Bogs Tidal flats and estuaries Rivers N 50 km Figure 13 Major wetlands types in the Netherlands. Modified from Best, E.P.H., Verhoeven, J.T.A., Wolff, W.J., 1993. The ecology of the Netherlands wetlands: characteristics, threats, prospects and perspectives for ecological research. Hydrobiologia 265, 305–319. the country, while concurrently changing the remaining estuarine bay to a 2120­km2 freshwater lake (Wolff, 1993). Some areas within these impoundments could not be drained, and thus resulted in a 65­km2 freshwater wetland 4 m below sea level (Wolff, 1993). At the start of the twenty­first century, the total surface area of reclaimed land exceeded 3500 km2 (Lintsen, 2002). In the southwest, several estuaries were dammed and converted to freshwater lakes (600 km2). The conversion of estuaries to freshwater lakes had the objective of reducing flood risks (by reducing the length of shoreline), reducing salinity intrusion through navigation channels, and improving freshwater supply for agriculture and drinking water (Smit et al., 1997). However, various unexpected nega­ tive effects of the conversion occurred, including accumulation of contaminated sediments, degradation of wildlife habitat in former intertidal areas, as well as algal blooms and fish kills in some areas (Smit et al., 1997). The landscape changes during the twentieth century reduced the coastline of the Netherlands from 3400 to 650 km (Lintsen, 2002). However, the total length of flood defenses (dike rings, dunes, etc.) to protect the Netherlands is nearly 3600 km. Without flood defenses, 65% of the most densely populated areas of the Netherlands would be flooded (Van Stokkom et al., 2002). 8.07.3.3.2 Wetland hydrology The hydrology of the Netherlands is dominated by the fresh­ water input from the Rhine River. With the headwaters in the Swiss Alps, the Rhine has a drainage area of 185 000 km2, receives runoff from six nations, and has an average annual discharge of 2300 m3s−1 (Middelkoop and Van Haselen, 1999). The Rhine contributes over half of the freshwater in the Netherlands water budget, while other rivers together add a quarter, and the remainder derives from local precipitation (Colenbrander, 1986). River water mainly influenced the flood plains and estuaries. The inland wetlands are located within a largely cultural landscape where water table and water quality are continuously managed (Best et al., 1993; Lamers et al., 2002). Groundwater tables are generally less than 1 m below the soil surface, and surface water is present in a dense network of ditches and small lakes (van Ek et al., 2000). Since the twentieth century, 10–20% of river water is extracted to supply a large part of the country with freshwater for human consumption, irrigation, countering saltwater 202 Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats 100 km N 100 AD 1200 AD River floodplains Tidal waters Dunes Fen mires Salt marshes Bogs Coastal marsh Tidal flats and estuaries Figure 14 Changes in wetland area in the Netherlands and Rhine River Delta. (a) Before human alterations, (b) small scale reclamation, From Wolff, W.J., 1993. Netherlands-wetlands. Hydrobiologia 265, 1–14. intrusion, and dilution of pollution (Wolff, 1993). Freshwater demand is driven by the intensive drainage for agriculture (Best et al., 1993). 8.07.3.3.3 Wetland types and current threats The Netherlands has a surface area of 41 864 km2 of which about 6600 km2 (16%) have been classified as internationally important wetlands (Wolff, 1993). The Dutch coastal ecosys­ tem consists of the extensive tidal flats of the Wadden Sea (2400 km2), estuaries (�760 km2), and dunes (400 km2) with small wet dune slacks (Best et al., 1993) (Figures 13 and 14). Inland wetland systems include shallow freshwater lakes (2260 km2), river flood plains (270 km2), fen mires in polders (�200 km2), and oligotrophic bogs and moorland pools (43 km2) (Best et al., 1993). Most threats to the Dutch wetlands are of man­made origin and include (1) changes in hydrology leading to changed discharges, currents, and desiccation; (2) acidification; (3) eutrophication; and (4) toxification (Best et al., 1993). Riverine nutrient discharges have increased, espe­ cially since the 1950s (Van Bennekom and Wetsteijn, 1990; De Jonge et al., 1996), while atmospheric nitrogen deposition is extremely high, mainly through ammonia emissions from agri­ cultural activities and nitrogen oxide emissions from combustion processes. In addition, fertilizer use in agriculture is one of the highest in the world (Bobbink et al., 1998; Gulati and van Donk, 2002). In the last half century, the Wadden Sea has experienced increases in phytoplankton biomass, with contemporaneous decreases in benthic algae in some areas and a large reduction in seagrass beds (Reise and Siebert, 1994; Cadée and Hegeman, 2002; van Beusekom, 2005). The overall increase in primary productivity of the Wadden Sea is correlated with the increases in riverine nutrient delivery (van Beusekom, 2005). In the inland wetland systems, the airborne N input has formed the principal N source for fens, even for the fens surrounded by heavily fertilized meadows. Another thread for the loss and degradation of fens is the altered drainage pattern and the use of river water to combat low water levels in agricultural areas (Beltman et al., 2000; Lamers et al., 2002). Freshwater lakes received inputs of nutrient­rich (N and P) and polluted waters from the rivers and canals, which were the heaviest in the mid­twentieth century (Gulati and van Donk, 2002). Although nutrient inputs have been reduced, ecosystem response has been slow, due to P storage in sediments, food­ web changes, and changes in shoreline vegetation (Gulati and van Donk, 2002). 8.07.3.3.4 Climate change Climate in the Netherlands is driven by the Gulf Stream, and changes are difficult to predict. Sea­level rise (mean relative sea­level rise estimated at 0.10–0.16 cm yr−1 – over the last two decades (Dijkema, 1990)) – threatens mainly the coastal wetlands, tidal flats, as well as salt marshes. The mainland salt marshes can withstand a rate of sea­level rise similar to the present because of increased accretion, but that may not be the case for the marshes on the barrier islands. The low­lying wetlands inside polders are currently protected through water management. Precipitation changes may cause the disappear­ ance of the last remaining ombrotrophic bogs (Casparie, 1993). Climate change is also predicted to increase winter Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats precipitation in the Rhine watershed which, combined with decreasing slope due to sea­level rise, increases the probability of river floods (Tol et al., 2003; Hudson et al., 2008). In addi­ tion, human alterations to the river course and watershed (e.g., weirs, dams, groins, diking of flood plains, and expanding impervious surfaces in urbanized areas) have increased the flashiness of floods (van Stokkom et al., 2002). The incremental reduction of space for the natural water system and changes in the water system itself have resulted in reduced safety, financial damage (floods, droughts, and dike breaks), and ecological damage (drought and loss of water quality). In the near future, the damage is expected to increase substantially and could be regarded as unsustainable symp­ toms of the current water system in the Netherlands (van der Brugge et al., 2005). The Netherlands is estimated to spend close to USD 3 billion yr−1 on water management, with 65% for water quality and 15% for flood protection. Even with this level of expenditure, 24% of the flood defenses are considered substandard. Flood risks are highest along the Rhine due to its high discharge and the presence of polders adjacent to the floodplain (Tol et al., 2003). Since the 1970s, civil engineering has given way to ecological engineering and rivers are no longer just transport channels, but important recreation areas and habitats. A near flood in 1995 prompted a large­scale evacua­ tion (250 000 people) and pointed out that the old ways of continuously raising and reinforcing dikes are insufficient in the face of increased human population and climate change (van Stokkom et al., 2002). In a country that struggled for centuries to gain every acre of arable land, the unthinkable is being put into practice – water returns (de Vriend and Iedema, 1995). New flood protection approaches emphasize the increase in discharge capacity by increasing the flood plain area (van Stokkom et al., 2002). This effort would convert these areas from agricultural to recreational and wildlife habitat. At the strategic level, the concept of the new water manage­ ment style is broadly shared, but at the operational level of implementation, there are numerous practical questions (van der Brugge et al., 2005). As long as there are severe incompa­ tibilities between the strategic level and the operational level, the strategy will not be implemented on the large scale that is needed for success. 8.07.3.4 Puerto Rico Island One of the most extreme scenarios when assessing the issue of physical space for wetland establishment and development in the context of human impacts and global changes is the case of islands. Indeed, islands in the tropical and subtropical oceans are some of the most vulnerable geomorphic features to sea­ level rise and the associated impacts of climate change. These impacts include changes in weather patterns (e.g., temperature, winds, and precipitation), sea­level rise, coastal erosion, changes in the frequency of extreme events (including potential increases in the intensity of tropical cyclones/hurricanes), reduced resilience of coastal wetlands, and saltwater intrusion into freshwater resources (Church et al., 2006); small islands could experience significant flood impacts during the twenty­ first century (Nicholls, 2004). It is expected that human dis­ turbances would have major negative effects on natural resources as a function of island dimensions and human 203 population size because resource utilization can drive major demands depending on societal needs and economic decisions. One dramatic example shows how societies characterized by distinct socioeconomic history and cultural legacy (i.e., Haiti and Dominican Republic), inhabiting the same island (Hispaniola) in the Caribbean, and using similar natural resource, can have dissimilar outcomes as a result of major differences in per capita income, population density, and growth rate (Diamond, 2005). Haiti, the poorest nation in the Western Hemisphere, with a population of 8.8 million, currently has only 1% of its original forest cover, and both coastal resources (e.g., fisheries) and water quality have dimi­ nished significantly, triggering major regional health problems and poverty. When analyzing historical trends in net aerial reduction of natural resources, including tropical forests and wetlands, it is paramount to take a close look at the nature of selective pres­ sures by human societies before establishing cause–effect relationships. A good example is the island of Puerto Rico, where recent studies show how the interaction between prior­ ities in resource utilization and human population density and economic policies can directly (sometimes unintended) facil­ itate the rehabilitation and conservation of forests and coastal wetlands at large spatial scales. Puerto Rico (population: 3.9 million) (18° 15′ N, 66° 30′ W) is the smallest island of the Caribbean Greater Antilles, with an area of 8900 km2 (55 � 160 km in size) (Figure 6). It is a mountainous island with elevation ranging from sea level to 1300 m. The island includes ecological life zones ranging from subtropical dry forests to subtropical rain forests, annual rainfall ranging from 900 to 5000 mm, and annual precipitation ranging from 750 mm in the southwest to 1500–2000 mm in the northeast to more than 4000 mm in the higher elevation. Mean annual temperature ranges from 19 to 26 °C. The largest climatic zone includes moist evergreen broadleaf forests (Ewel and Whitmore, 1973). The geology of the island includes sedimen­ tary rocks on the north and south coasts, old volcanic and sedimentary rocks in the central mountainous area, and some serpentine soils (Grau et al., 2003; Boose et al., 2004). Puerto Rico and adjacent islands of the Caribbean (e.g., Hispaniola, Cuba, and Jamaica) are subject to frequent and severe impacts from hurricanes, including wind damage to forests, scouring and flooding of river channels, landslides triggered by heavy rains, and saltwater inundation along shore­ lines (Boose et al., 2004). It is estimated that 95 342 ha are occupied by developed lands equivalent to 11–14% of the island, particularly in coastal areas (Martinuzzi et al., 2007). Landscapes with flat topography, nutrient­rich soils, and moist climates are occupied much faster by humans than landscapes with steep topography, nutrient­poor soils, and unfavorable climates, especially once vehicular accessibility is improved (Chomitz and Gray, 1996; Lugo, 2002). As in many islands with high relief, urban centers in Puerto Rico are concentrated on the coastal plains or restricted to valleys. Urban develop­ ments have grown 7% between 1991 and 2000. These settlements expand at lower elevations, over flat topography, and close to roads and urbanized areas (Thomlinson et al., 1996; Thomlinson and Rivera, 2000; del López et al., 2001; Martinuzzi et al., 2007), and are promoted by an extensive rural­road network developed during the agricultural era (Martinuzzi et al., 2007) (Figure 15). 204 Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats Evaluating human use and development of the landscape is far more complex than simply mapping the urban and agricul­ ture cover, independent of the spatial resolution and detail obtained (Lugo, 2002, 2006). Improvement depends on the ability to analyze both the extent and type of changes in devel­ oped land surfaces, qualify the types of development, analyze how urban developments are distributed across the landscape, and how they associate with population distribution (Martinuzzi, et al., 2007). Thus, one major question in the case of Puerto Rico is how coastal and freshwater wetland habitats are modified under a scenario of limited space and increasing human population, particularly in societies where the economies shifted from agriculture to industry in less than 60 years (Figure 15). Indeed, Puerto Rico is a prime example of this process, which is characteristic of developing countries in the neotropics (Dietz (1986) in Grau et al. (2003); Lugo, 2002). Land­cover change is very intense in tropical developing countries that are typified by agriculture­based economies and rapidly increasing human populations (Grau et al., 2003). Although plant ecolog­ ical research has been conducted in Puerto Rico since the early 1900s, there is not much information on the spatial and tem­ poral changes in wetland (inland and coastal) distribution and extension (Lugo and Waide, 1993). Major emphasis has been on vegetation changes in extension forest at high latitudes. Yet, it is recognized that large areas of forested wetlands have been impacted with a steady decline since the 1920s. Wetland reduc­ tion is linked to agriculture development, which affects water availability and wetland habitat. Martinuzzi et al. (2007) showed that 60% of the total developments occur in the plains, where the most productive lands for agriculture are located; in contrast, in hills and mountains, the presence of developed areas represents <7% of their total expanse. Landscape analyses of urban development in Puerto Rico clearly show the contiguity between the compact urban areas in coastal areas. This urban footprint is easily distinguished as a major coastal ‘urban ring’ that surrounds the island with cor­ responding minor rings that encircle interior mountainous and protected areas and national parks (Lugo, 2002; Martinuzzi, et al., 2007). Currently, within this coastal ring, the areas of developed and nondeveloped land are similar (�70 000 ha) (Martinuzzi et al., 2007). Contrary to the general trend of deforestation in the tropics (Turner et al., 1990; DeFries et al., 2000; Watson et al., 2001), the main result of Puerto Rican socioeconomic changes has been a process of forest recovery (Lugo, 2002). In the late 1930s, about 90% of land cover in Puerto Rico was some form of agriculture (Dietz, 1986; Birdsey and Weaver, 1987), but by 1991, forest covered 42% of the island (Helmer et al., 2002). During the agricultural era, which started in the 1800s, the island was almost completely defo­ rested, with only about 6% of the original forest cover remaining by 1948 (Birdsey and Weaver, 1987). By the late nineteenth century, pasture covered >55% of Puerto Rico as forest clearance and agriculture reached a peak (García Montiel and Scatena, 1994). This land transformation was associated with a human population density increase from 1912 (220 km2) to 2000 (455 km2) (Figure 15). A 100% change in population density coincided with an unexpected change in the economic activity of the island from agrarian to manufacturing services, triggering population migrations to urban centers, and, as a consequence, an increase in forest area (Lugo, 1996; Rivera Batiz and Santiago, 1996; Grau et al., 2003, 2004; Lugo, 1991). As an unplanned consequence, the coastal lowlands today are dominated by humans (i.e., urban develop­ ments, industries, pastures, and agricultural/hay fields) (Lugo, 2008; Martinuzzi et al., 2009) 800 000 Crops and Forest area (ha) Crops 600 000 With forest 400 000 200 000 Human population × 10 0 1700 1750 1800 1850 1900 1950 2000 Years Figure 15 Changes in land use and population in Puerto Rico during the last three centuries with details in the twentieth century. As in many islands with high relief, urban centers in Puerto Rico are concentrated on the coastal plains or restricted to valleys. Urban developments increased 7% between 1991 and 2000. From Lugo, A., 2006. Ecological lessons from an Island that has experiences it all. Ecotropicos 19, 57–71. Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats Among representative examples of the degree of human impacts on wetland habitat in Puerto Rico is the case of palm forest (Prestoea Montana), blood wood (Pterocarpus officinalis), and mangrove forests (Figure 16). Palm tree is a dominant species with wide distribution watersheds, whereas blood wood is a ubiquitous tree species of coastal wetlands in the Caribbean and Guiana regions, and one of the main constitu­ ents of coastal freshwater­forested wetlands (Bacon, 1990). Both species represent vegetation associations that have dimi­ nished in area because of major hydrological modifications for agriculture and water storage (dams and irrigation). For exam­ ple, current blood wood extension represents only 20% of the original forests (Medina et al., 2007). The high rainfall envi­ ronment of Puerto Rico is linked to the development of hydraulically efficient drainage systems (Smith et al., 2005), and when there is interaction with a steep relief, a conspicuous salinity gradient develops influencing the spatial distribution of wetlands at lower elevations and at the boundary with the coastal zone. Freshwater­forested wetlands occur right behind the mangrove belt and P. officinalis can grow in slightly brackish waters (Tomlinson, 1995; Bonheme et al., 1998; Imbert et al., 2000; Rivera­Ocasio et al., 2002). Ecophysiological studies suggest that P. officinalis is probably a species best adapted to flooding in freshwater­forested wetlands and shows a degree of tolerance to soil salinity derived from seawater in coastal sites under tidal influence (Bacon, 1990; Medina et al., 2007). Vegetation distribution is clearly delimited by the salinity gra­ dient where vegetation associations of Typha sp. (cattail)– Acrostichum sp. are found at the freshwater side and L. racemosa, a dominant mangrove species, at the brackish side. Mangrove forests are conspicuous vegetation in Puerto Rico as in most tropical and subtropical coastal regions, and they are one of the most vulnerable coastal wetlands to human impacts (Lugo et al., 2007). The dramatic changes in mangrove cover in the coastal regions of Puerto Rico since the 1800s to the early 2000s show the role humans have played in controlling vegetation patterns through land use (Figure 16). These practices included intensive agriculture and conversion to urban areas that resulted in significant decline of mangrove area recent gains. 205 Recently, Martinuzzi et al. (2009) evaluated how in a few decades the lowlands were transformed from an agricultural into an urban/residential landscape. The lowlands were the most deforested regions due to their flat topography, moist climate, and rich soils. However, they found that, in the case of mangrove wetlands, mangrove extension increased despite an increase in population density. They noticed distinct periods of mangrove area use from 1800 to 2000. The first period, identified as agricultural, was from 1800 to 1938 as it corres­ ponded to most of the agricultural expansion era of the island. During this period, the area of mangrove decreased by 45% from 11 791 ha to 6475 ha when lowlands were transformed into sugar cane fields and pastures. Mangrove wetlands were extensively used for fuel wood and charcoal, and stands were converted to agricultural fields. The hydrology of coastal wet­ lands was altered mostly by drainage to protect agricultural crops or for irrigation (Martinuzzi et al., 2009). A number of mangrove forests were converted to housing developments and garbage dumps and urban drainages were channeled through mangroves; garbage deposition slowly filled these wetlands, accelerating conversion. Between 1977 and 2002, the man­ grove cover of Puerto Rico increased by 12%, from 7443 to 8323 ha. However, from all the sites analyzed by Martinuzzi et al. (2009), mangrove area increased in 50% of them, did not change in 30%, and was reduced in 20% (Figure 16). Although population growth in Puerto Rico targeted coastal regions during the second half of the twentieth century, the pooled effect of legal protection of all mangroves, restoration of wetlands, and the end of the sugar cane industry resulted in a rapid increase in the total area of mangroves (Lugo, 2006). Concurrently, trends of human population and forest cover also increased on the island. This positive trend in both cases is counterintuitive if we consider other studies from coastal areas where wetlands have been decimated as population increases. Lugo (2002) and other investigators argued that special care should be taken when equating human activity with human population pressure at the global scale. Other studies have shown that indeed at local and regional scales human activity can have a devastating effect on mangrove extension and spatial distribution. For example, shrimp Agricultural period Industrial period Mangroves (thousands of ha) 13 12 (1) Decline for agriculture 11 (2) Natural recovery 10 (3) Decline for urbanization 9 8 7 (4) Recovery under protection 6 5 1800 1820 1840 1860 1880 1900 1920 Year 1919 1940 Legal protection of five insular forests with mangroves 1960 1980 2000 1972 Legal protection of all mangroves in the island Figure 16 Mangrove area cover in Puerto Rico, including four historical periods of change (parentheses). From Martinuzzi S., W.A. Gould, A.E. Lugo, and E. Medina. 2009. Conversion and Recovery of Puerto Rican Mangroves: 200 Years of Change. Forest Ecology and Management 257, 75–84. 206 Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats mariculture had a large negative effect on mangrove forests in Southeast Asia and South America during the 1980s and 1990s; however, the mariculture impacts were related to actual land­ management decisions, not to an increase in human popula­ tion density because mangroves are strongly affected, for example, by changes in hydrology (Lugo, 2002, 2006; Martinuzzi et al., 2009). One extreme example of this scenario in the continental neotropics is the Cienaga Grande de Santa Marta, Colombia, where approximately 350 km2 of mangrove area was lost in a region where population density was steady during the 1980s and 1990s; the major reason for this man­ grove die­back was salt accumulation in the soil (hypersalinity) as a result of roads and levee construction that impacted local hydrology (Botero and Salzwedel, 1999; Rivera­Monroy et al., 2004; Rivera­Monroy et al., 2006). There is no question that mangrove gains in Puerto Rican coastal areas were not only the result of natural regeneration in abandoned areas historically used for agriculture or urban development, but also a consequence of implementing laws protecting these wetlands (Figure 16) (Martinuzzi et al., 2009). Other forest types that used to be common in Puerto Rico lowlands, but did not benefit from such protection (e.g., ripa­ rian and alluvial forests and Pterocarpus swamps), are currently almost nonexistent (Lugo, 2005). The recent recovery of man­ groves is therefore the result of a combined effect of natural recovery under legal protection. Indeed, Grau et al. (2003) pointed out that the dramatic shift in the land­use and land­ cover history of Puerto Rico could be considered a ‘large­scale ecological experiment’, allowing an assessment of the resilience of an ecosystem of almost 1 million ha that was submitted to intense human disturbance for approximately a century and later progressively abandoned. Yet, the ‘experiment’ continues because it should be recognized that forest recovery in upland and coastal regions in this tropical island was an unexpected result of political and socioeconomic change and not necessar­ ily from a planned decision to improve or optimize the island complex landscape mosaic (Lugo, 2002). Pressing economic and social decisions are waiting in the near future as Puerto Rico, shifting from an agrarian to an industrial/urban society, faces increasing demands for basic goods (e.g., food) and services to support its increasing popu­ lation and long­term sustainability. As Puerto Rico’s natural and human communities are strongly shaped by hurricanes, a critical question is how an increase in hurricane frequency and strength would alter this interaction; although current land­use patterns indicate that human disturbances might have a major role in the short term, hurricanes can play a role in the long term given their spatial and temporal scale of occurrence. In addition, impacts of sea­level rise on coastal wetlands in Puerto Rico could be significant, but human­induced direct and indi­ rect effects are potentially much larger based on existing trends. Furthermore, studies assessing how hurricane and sea­level rise will interact to influence the availability of coastal region eco­ logical goods and services for the strategic growth of the Puerto Rican economy are lacking. Certainly, changes in the landscape at the temporal and spatial scales observed in Puerto Rico are a good lesson to begin assessing the relative importance of planned and unplanned decision making in terms of coastal management (Figure 6). Directing human activities that facili­ tate the limitation of urban growth boundaries and increase conservation areas will contribute to our understanding of the causes and consequences of natural and human­induced processes in coastal ecosystems. 8.07.3.5 Everglades, South Florida, USA South Florida’s Everglades, in contrast to the heavily developed Louisiana coast, are protected by the US National Park Service (Twilley, 2007), with additional international designation as a biosphere reserve, a world heritage site, and a wetland of inter­ national importance (Rivera­Monroy et al., 2004; Sklar et al., 2005). The Everglades National Park is also located within a watershed of intensive human development, with one of the largest urban and agricultural regions to the north and east of the park boundary (Harwell et al., 1996; Harwell, 1998). The direct economic impact of the Everglades is illustrated by its role as the fundamental basis for a USD 18 billion recreation and tourism industry. The landscape of South Florida before European settlement was a mosaic of habitats connected by the flow of freshwater across a gently sloping landscape from Lake Okeechobee through the Everglades and south to Florida Bay (Light and Dineen, 1994; Harwell et al., 1996) (Figure 17(a)). The wet­ land landscape included saw grass interspersed with tree islands, with mangrove forest extending over an area of 3 million acres in the estuarine transition zone (Gunderson, 1994). The natural evolution of the region was driven in part by the very slow eustatic rise in sea level over the past ∼4 000 years developed on gently sloping limestone bedrock. The ecosystem was shaped by extreme episodic events such as fires, freezes, hurricanes, floods, and droughts; it evolved under a low­nutrient (phosphorus) regime, making much of the native flora susceptible to impacts of nutrient enrichment. Surface water flowed out of Lake Okeechobee and traveled by sheet flow through extensive saw­grass plains, eventually reach­ ing Florida Bay at the southern tip of Florida. Today, the major components of the drainage basin of the Everglades system include (1) the Kissimmee River; (2) Lake Okeechobee, which historically provided the Everglades with the freshwater overland flow; (3) the Everglades Agricultural Area (EAA), a large tract of the northern Everglades imme­ diately to the south of Lake Okeechobee which has been drained for agriculture; (4) the Water Conservation Areas (WCAs), large tracts of the northern Everglades immediately south of the EAA where the marsh has been impounded by a series of berms and has essentially been used as a surface reservoir for water storage; and (5) the Everglades National Park, south of the WCAs, which is protected as a national park, stretching south and west to Florida Bay (Figure 17(a)). Overall, the Everglades ecosystem has lost approximately 8094 km2 of its original 16 188 km2 area. The losses are pri­ marily attributed to the drainage of land for agriculture and development, including a network of canals, which drain the agricultural lands and transport water to the developed coastal region, discharging excess runoff to the estuaries and coastal ocean. With the loss of acreage of wetland, important ecologi­ cal functions, including habitat for a wide range of organisms, surface water storage, and carbon storage, have all been dramat­ ically reduced. The Everglades Restoration is the world’s largest wetland restoration project ever undertaken by humanity (USD �8 billion) (Figure 17(b)). The following distinct components make up the drainage basin, and water flow is essentially Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats 207 (a) Lake Okeechobee West Palm Beach Everglades Agriculltural Area WCA-1 WCA2A 2B Fort Lauderdale WCA–3 Big Cypress Miami Everglades National park (b) Historic flow Current flow The plan (CERP) flow Figure 17 (a) The Everglades landscape as it is thought to have appeared prior to development compared with today’s highly managed, compartmentalized system; (b) historic, current, planned water flow conditions under CERP in Everglades Watershed. (a) From Sklar, F.H., Chimney, M.J., Newman, S., McCormick, P., Gawlik, D., Miao, S.L., McVoy, C., Said, W., Newman, J., Coronado, C., Crozier, G., Korvela, M., Rutchey, K., 2005. The ecological–societal underpinnings of Everglades restoration. Frontiers in Ecology and the Environment 3, 161–169. (b) Source: http://www.evergladesplan.org managed within a single state governmental organization (South Florida Water Management District). which flowed quickly into Lake Okeechobee under the chan­ nelized system. 8.07.3.5.1 8.07.3.5.2 Kissimmee River The Kissimmee River contained over 160 km of meandering river, which seasonally flooded as much as 4.8 km either side of the main river channel during the wet season, providing water and nutrients to a diverse riparian wetland community. After severe flooding from two hurricanes in the 1940s, the state of Florida requested federal assistance from the US Army COE, which shortened the 166­km meandering river channel distance from Lake Kissimmee to Lake Okeechobee to just 90 km. Over 160 km² of floodplain area were drained as a result of the river­channel straightening, and estimates suggest this reduced the waterfowl habitat by 90%. In addition, there was a concomitant loss of water­quality amelioration associated with the loss of riparian wetland acreage as well as storage of water Lake Okeechobee Lake Okeechobee is a large, subtropical freshwater lake and is the largest such lake contained wholly within US borders excluding the Great Lakes. The initial attempts at controlling the water began in the 1910s when a small earthen dike was constructed to prevent flooding from Lake Okeechobee into the surrounding developed areas. This modest containment was breached by flooding and large seiches set into motion from hurricanes in 1926 and 1928, killing thousands of people and cattle from floodwaters. After these disasters, the Florida State Legislature created the Okeechobee Flood Control District, which was authorized to cooperate with the US Army Corp of Engineers to deal with flooding issues. The US Army COE drafted a new plan, which provided for the construction 208 Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats of floodway channels, control gates, and major levees along the shores of Lake Okeechobee to contain the lake during high water. In the 1930s, a larger system of levees was built around the lake. Following heavy precipitation and flooding from two hurricanes in 1947, the dike was again expanded in the 1960s to create the current Herbert Hoover Dike. The cost of construc­ tion was about USD 165 million, and it now towers about 9 m high, providing an immense storage capacity of water within the lake. However, it prevents the lake from expanding as it once did into the surrounding marsh when the rainy season prevailed. Therefore, the lake has lost seasonally flooded habi­ tat, which cannot be recovered as development increased in close proximity to the levee. The Kissimmee River flows into Lake Okeechobee at the north, and the water not discharged to the east or west flows into the EAA. Other than rainfall, this water essentially provides all the freshwater to the Everglades system unless redirected to the coastal urban communities. 8.07.3.5.3 Everglades Agricultural Area The area south of the lake, known as the EAA, was primarily saw­grass marsh and was drained by a series of canals and water control structures conveying the water toward the east coast and setting the basis for large­scale agriculture operations. The EAA was carved from approximately 28% of the presettlement Everglades, and today it occupies an area of 2833 km2. The soils are productive peats and mucks and are now oxidizing because of the drainage of the surface water, leading to subsidence of the soil surface at a rate of 1–3 cm yr−1. The majority of the area is under sugarcane production with some limited winter vege­ tables and sod production. During high rainfall events, the water on the agricultural lands is pumped out and is either sent along canals to the east coast where much of the freshwater is lost to the sea or diverted into the adjacent WCAs. movement into and through the network of interconnected WCAs. The surface water originates from Lake Okeechobee and passes through the EAA, where the water becomes enriched with nitrogen and phosphorus, a consequence of the agricul­ tural activities. This nutrient­rich water has historically flowed into the WCAs, changing the ecology of the marsh from the microbial communities, the plants, and the habitat value. While once a vast saw­grass marsh separated by shallow, open water sloughs, dense stands of cattail have invaded at the sur­ face water inflow points. This invasion is coincident with changes in hydrology and high phosphorus. The US Federal government initiated a lawsuit challenging the use of the WCAs essentially as treatment wetlands by the State of Florida. Although the point of the STA was to store water, the nutrients contained within the surface water were found to be driving changes in the native flora of this phosphorus­limited system (Richardson et al., 2007). The US Federal government and the State of Florida brokered an agree­ ment to each pay half of the restoration costs, which exceed USD8 billion. The restoration plans have been continually reviewed and revised but have essentially focused on the con­ struction of the STAs to intercept and remove nutrients from surface waters as well as management of the agricultural area to reduce nutrient runoff. 8.07.3.5.6 The Everglades National Park The stormwater treatment areas (STAs) consist of six con­ structed wetlands covering more than 166 km2 that have been built at the southern end of the EAA with the goal of intercept­ ing the high nutrient runoff from the agricultural lands and removing phosphorus prior to discharge into the WCAs. STA 3/4, at 69 km2, is the largest constructed wetland in the world. This area is perhaps one of the few places in the world where constructed wetlands are used to remove nutrients prior to discharge into a natural wetland. The STAs were originally designed to use natural processes to lower the phosphorus concentrations from 100 ppb down to 50 ppb. Today, most of them are removing phosphorus to far lower (15–25 ppb) values (White et al., 2004; White et al., 2006). One additional benefit of building these wetlands on the agricultural lands is that it returned the previously drained Everglades marsh back to wetland. The vegetation responsible for nutrient removal includes spike rush, cattail, water hyacinth, and algae, and the STAs host a wide range of fauna including wading birds, alli­ gators, and turtles. The Everglades National Park with an area of 6070.3 km2 is the third largest national park in the contiguous United States, behind Death Valley and Yellowstone National Parks. The park was established in 1934 by law, but land acquisition was halted during World War II and was finally dedicated by President Truman in December 1947. It was the first national park established not for its scenic vistas but for the magnifi­ cence of its biological resources. The habitats are vast and varied and include saw grass marshes, hardwood hammocks, mangrove swamps, lakes, and Florida Bay to the south and west. The coastal margins of the Everglades are dominated by mangrove forest. Soil accretion and elevation in the Everglades are dominated by plant productivity, producing highly organic soils in the absence of significant river sediment deposition (Lynch et al., 1989; Parkinson et al., 1994; Whelan et al., 2005). Although mangrove situated at the mouth of estuaries in the southwest Everglades experiences pulsed input of sediment during storm events (Chen and Twilley, 1998; Chen and Twilley, 1999), the Everglades as a whole rely on in situ or autochthonous organic soil production. Hence, the rate of soil building in the Everglades is governed primarily by plant productivity, nutrient delivery, and flooding status. Because subsidence in the Everglades is insignificant, plant vulnerability is related mainly to the rise in sea level relative to the rate of soil formation. Soil­building processes in the Everglades have been altered by the engineered water management systems (Twilley, 2007). 8.07.3.5.5 8.07.3.5.7 8.07.3.5.4 Stormwater treatment areas Water Conservation Areas The northern Everglades consist of impounded, shallow reser­ voirs called the WCAs. These are tracts (3500 km2) of saw­grass marsh that have been surrounded by low, earthen dikes in the 1960s to provide water­storage capacity during the wet season. Water control structures are used to meter surface­water Restoration issues There are a number of issues related to the Everglades restora­ tion, and their importance varies depending on the part of the system investigated. For example, the EAA has an organic­rich peat soil that has been drained to provide for arable land for agriculture. Consequently, the land has been subsiding due to Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats oxidation of the organic soils, and the surface of the land is now as much as 3+ m lower than it was in the early 1900s. Much of the organic soil, which took thousands of years to accrete, is nearly gone with the limestone bedrock exposed at the surface. Although some people would like to see the agricul­ tural lands flooded and returned to Everglades marsh, this is not likely possible at this point because of the subsidence. Any attempt to flood the area on a large scale would most likely result in the formation of a lake and not the saw­grass­dominated wetland that once covered the area. If farming were abandoned on the land, it would take millions of US dollars each year to control the invasive species that would carpet the landscape. Additionally, there are towns, roads, and other infrastructure elements among the agricultural lands, and the question remains, what would become of them, their people, their economy, and their history? This expensive lesson was learned in the Everglades National Park where limited agriculture was ceased in the 1960s and without a land­management plan, and the former agricul­ tural land was overrun with an exotic, Brazilian Pepper (Schinus terebinthifolius). That land is now being reclaimed back to natural vegetation at a cost through mitigation banking of �USD 1 million per acre. Consequently, it might be impossible to recap­ ture the original habitat of the EAA now that the local topography has been altered. For the WCAs, the high concentration of phosphorus is the biggest issue. Since the Everglades evolved as a P­limited sys­ tem, much of the flora and fauna are adapted to survive in an oligotrophic environment (Noe et al., 2001). Once the P limi­ tation was removed by directing agricultural drainage into the WCAs, other species were able to proliferate which did not thrive in the low P conditions. Cattail (Typha) was the major invading macrophyte, growing in very dense, tall stands, which shaded out the slower­growing saw grass and quickly filled in the open slough areas, which is vital habitat for wading birds. The rate of cattail expansion increased from 1% to 4% per year between 1971 and 1987 due in part to an increase in soil P (Wu et al., 1997). The wetlands of the STA are now in place and intercept much of the phosphorus before the surface waters are directed into the WCAs. However, there are high phosphorus wetland soils (4–5 times higher than the concentration of unimpacted Everglades peat soil), which have developed, prox­ imal to the surface water inflow points from the past nutrient loading. These soils contain 4–5 times more P than natural Everglade’s soils. As low P water is introduced into the WCAs, there is a legitimate concern that the P will be mobilized, diffusing up into the water column and spreading the areas of eutrophication deeper into the WCAs (Fisher and Reddy, 2001). At the current time, there is no plan to deal with this high soil P, which could potentially spread farther into the Everglades and lead to further losses of wading bird habitat as the invasive cattails expand. Another issue that affects not only the WCAs but also the Everglades National Park is the water supply requirements of the 7 million inhabitants of the eastern margin urban corridor stretching from West Palm Beach south to the Miami area. This urban area is the second longest urban area in the contiguous US, stretching 175 km in the N–S direction and ranging from 8 up to 32 km wide (E–W), bounded by the Atlantic Ocean on the east and the Everglades on the west. As �70% of the rainfall in South Florida occurs during the four to five rainy season months, there is a considerable water deficit for much of the 209 year. The population requirements for water, however, are constant and concerns exist over whether any agreements for water delivery to the Everglades National Park will be honored when such a large population requires freshwater during dry periods or droughts (Figure 6). 8.07.3.5.8 Successful restoration The Kissimmee River restoration is an example of a successful restoration project at the northern end of the drainage basin costing close to USD 500 million. The Kissimmee River Restoration Project is focused on restoring the integrity of the river by backfilling the middle one­third of the river to restore flow, the adjacent riparian floodplain wetland along with other benefits of the original pre­channelized system. The project is restoring over 100 km2 of river/floodplain ecosystem, includ­ ing 69 km of meandering river channel and 10 927 ha of wetlands. Before the C­38 Canal was dug in the 1960s, the Kissimmee snaked 165 km through Central Florida, from Lake Kissimmee to Lake Okeechobee. The river’s floodplain, 4.8 km wide in places, held seasonal rains for long periods. Although only one­third of the river is being restored, it is still the largest river restoration project of its kind at project inception. 8.07.3.5.9 The fight for water The subsequent wetland habitat alterations and concomitant reduction in wading birds populations are implied to be related to the drainage of the area, consequently reducing the sustai­ nability of the region’s natural resources. This water control system has also been used to divert critical surface­water resources away from the protected Everglades National Park during the dry season when it is most critically needed. The water flowed toward the densely populated urban areas crammed in a narrow strip of former beach ridge and barrier islands along the southeastern portion of peninsular Florida. The area from West Palm Beach southward to Miami and Homestead, a distance of approximately 120 km, contains over 7 million people with significant freshwater demands. As a result, the Everglades is now an endangered ecosystem, and the vulnerability has increased due to projected climate change and sea­level rise (Harwell et al., 1996; Harwell, 1998). Despite the engineered water­storage capacity of Everglades System, a tremendous amount of water is ‘lost to tide’ through drainage canals to deal with flooding. 8.07.4 Summary and Final Comments During the last 20 years, a solid conceptual framework has been developed to help us understand the environmental drivers that regulate the structural and productivity patterns of wetland ecosystems. The implementation of conservation and manage­ ment efforts that take into consideration strategies based on sound scientific information is urgently needed. This informa­ tion has been obtained at various temporal and spatial scales across various latitudes for ecosystems with various degrees of disturbance, allowing for the identification of many causes and effects associated with wetland degradation. There is no ques­ tion that when designing wetland management and restoration plans, social, economic, and political processes need to be considered to maximize such effort. 210 Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats The examples presented in this chapter underline the dynamic interaction between human actions and wetland habi­ tat reduction at local and global scales. These issues define well the scope of ‘human use and abuses’ of productive ecosystems vital for the sustainability of both poor and rich nations. The causes and effects, associated with the loss of space, area, and habitats, are complex and exacerbated, in many cases, by the lack of understanding of ecosystem trajectories not only in less impacted regions (e.g., ‘pristine’, Grijalva–Usuamacinta Delta) but also in heavily altered ecosystems (e.g., Mississippi River Delta, the Netherlands, and Florida Everglades) (Table 5). As previously mentioned, in most cases, the lack of a clear definition of what action(s) is being implemented (i.e., reha­ bilitation vs. restoration) in coastal management plans complicates the identification of factors (and their interactions) responsible for various ecosystem and, sometimes, surprising ecosystem trajectories (e.g., natural reforestation and natural regeneration of mangroves in Puerto Rico). The human impact described for each site included in this comparative analysis clearly represents major impacts identi­ fied for coastal wetland ecosystems around the world (Tables 1 and 5). The common direct human impact is the alteration of the hydrology and associated hydroperiod, which steadily trig­ gers wetland area loss, thus reducing economically valuable ecosystems goods and services (e.g., pollution control, storm protection, carbon sequestration, habitat support, and food). The long­term interaction and accumulation of natural and Table 5 human impacts certainly affect ecosystem integrity as in the case of coastal Louisiana and the Everglades regions, which are ecosystems drastically different in productivity and structure in comparison to 100 years ago. Although sea­level rise is a com­ mon, direct natural impact at all sites (Table 5), its influence will depend on the regulatory effect of both natural and human process at different temporal and spatial scales. For example, wetlands in the Mississippi and Grijalva deltaic regions are affected by broad­scale patterns of climate (including hurri­ canes), topography, geology, and land use that control sediment erosion and transport to the coastal zone. Nevertheless, at smaller scales, wetlands are influenced by human impacts such as canalization and levee construction along the major tributary rivers and through wetlands, thus impeding the distribution and deposition of sediment. It is the combination of these natural and human­induced changes in the landscape that will determine potential storm damage to inland regions (Hopkinson et al., 2008). In contrast, subsi­ dence represents a local effect closely related to the regional geology; however, in combination with human activities (e.g., oil exploration and groundwater extraction in Louisiana), it has become a major driver in controlling soil elevation and hence vegetation distribution and flooding regimes. Puerto Rico, as an example of an oceanic island significantly impacted by hurricanes, shows how natural systems respond to urban devel­ opment driven by major shifts in resource utilization, resulting from economic decisions. However, in order to assess the role Environmental characteristics and human impacts on selected wetland ecosystems discussed in this chapter Environmental characteristics Mississippi River Basin-Coastal Puerto Rico Southern Coast Southern Everglades Grijalva–Mezcalapa– Usumacinta The Netherlands Central coast Country Geomorphologic setting Wetland type The USA Delta Puerto Rico Oceanic Island The USA Karstic Mexico Delta The Netherlands Delta Bottomland hardwood forest, swamps, marshes 8500 Stream channeliziation and dredging; flood control, canalization; water pollution–urban and agricultural Land subsidence due to groundwater, resource extraction, and river alternations Mangrove forests, palms Sawgrass, swamps, mangrove forests Freshwater wetlands, mangrove forests �1100 Deforestation, urban development 34 000 Stream channelazitation and dredging; flood control; agriculture, urban development Hydrologic alteration by roads, canals, etc. Hydrologic alteration by roads, canals, etc.; land subsidence due to groundwater, resource extraction, and river alternations 20 000 Dam construction, urban development, hydrological modifications; oil extraction; water pollution–urban and agricultural Sediment retention by dams and other structures; Hydrologic alteration by roads, canals, etc. Coastal marshes, salt marshes, fens/mires/ bogs 2644 Agriculture, sedimentation, hydrological modifications Sea-level rise; hurricanes and other storms No; natural regeneration Sea-level rise; hurricanes and other storms Subsidence; Sea-level rise; hurricanes and other storms Yes; Levee removal; freshwater diversion No Area (km2) Major human impact: Direct Major human impact: Indirect Natural event Rehabilitation– restoration Program/ actions Subsidence; sealevel rise; hurricanes and other storms Yes; freshwater diversion; levee removal; sediment redistribution Hydrologic alteration by roads, canals, etc; sediment retention by dams and other structures Subsidence; sealevel rise; storms Yes, levee removal; freshwater diversion Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats of these interactions between human and natural disturbances, long­term information at different spatial scales is needed to estimate the contribution of each driver to the total variation in ecosystem properties before and after major ecological changes. Major scientific efforts are now underway to develop regional and continental­scale coastal networks to adequately under­ stand various scales of current and future wetland loss (Zhang et al., 2004; Hopkinson et al., 2008). We would like to stress that the ever­evolving wetland science conceptual framework has provided critical informa­ tion to ameliorate and correct, to a certain degree, human impacts on wetland ecosystems, particularly during the last two decades (e.g., Kissimmee River). The cumulative know­ ledge about the role of wetlands in maintaining water quality or their ecological function as habitat for birds and economi­ cally important fisheries has become part of the narrative in textbooks making it difficult to argue against wetland conserva­ tion programs (Fraser and Keddy, 2005; Mitsch and Gosselink, 2007; Mitsch et al., 2009). Further advances in technology have provided wetland ecologists with inexpensive and reliable environmental sensors to understand on large temporal and spatial scales, for example, the critical role of hydroperiod in controlling wetland productivity and how human impacts trigger wetland degradation as a result of changes in the hydrology (and salinity) of entire watersheds. However, looking at historical changes in wetland habitat coverage around the world and, in particular, at the aforementioned case studies, it is breathtaking to learn that, despite the well­known consequences of specific management decisions leading to wetland loss and degradation over the past decades (e.g., navigational channels, urban and agricultural develop­ ment, and hydrologic modification), such decisions are recurrent and are more often the rule rather than the exception; thus, the pressing question is, “Why?” Part of the answer is found in the failure to identify that wetland ecosystems, as part of the environment, interact with economic and social processes to form a system. Dynamic interactions take place between the natural and socioeconomic systems and, instead of being considered as two separate entities that exist independently of each other, they should be viewed as developing in a co­evolutionary way (Klein and Nicholls, 1999). It seems that despite a large volume of infor­ mation on well­known causes of wetland degradation and losses in all continents (e.g., Lehner and Döll, 2004), policy decisions are made based on isolated social and economic priorities (Walker, 2005). For example, the recently well­ published civil court case against the US Army COE related to the role of the Mississippi River Gulf Outlet (MRGO), which allegedly contributed to the loss of vast wetland areas and ultimately to the flooding of New Orleans during Hurricanes Katrina and Rita in 2005. MRGO is a ‘short­cut’ navigation channel that was con­ structed in the 1960s for approximately USD 92 million; it is 122 km long, 11 m deep, and 198 m wide at the surface. It was constructed to provide an alternate and shorter route for cargo ships (deep­draft shipping) from New Orleans to the Gulf of Mexico. Thus, the rationale for MRGO construction was pri­ marily economic, because the 64­km shorter route through the St. Bernard region promised a safer and more efficient passage than the Mississippi River below New Orleans. Proponents originally argued for the project as a way of great industrial 211 development for St. Bernard Parish. However, as a result of the direct connection, marine water intrusion increased salinity in cypress swamps and other inland wetlands, killing vegetation, particularly in the eastern region of New Orleans. Wetland habitats that have been lost or severely degraded include 14 km2 of fresh/intermediate marsh; 42 km2 of brackish marsh; 17 km2 of saline marsh; and 6 km2 of cypress swamps and levee forest (Caffey and Leblanc, 2002). As a result of this habitat loss, waterfowl use of wetlands has also declined; pre­ project waterfowl in fresh and intermediate marshes supported more than 250 000 wintering ducks and annual fur harvest of more than 650 000 animals (Kerlin, 1979). In addition, envi­ ronmentalists claim that this vegetation was vital to help the area absorb storm surge associated with hurricanes, and, to further compound the situation, the alignment of the channel created a ‘funnel’ that facilitated inland movement of storm surge. The civil case against the COE was presented in United States District Court in New Orleans in late spring 2009. Six plaintiffs presented their case against the COE to a district judge requesting payment for potential flooding damages of up to USD 100 billion. The plaintiffs claim that MRGO introduced a grave risk to a fragile levee­protection system, while the govern­ ment argued that the magnitude of the storm (category 3), by itself, caused the flooding of New Orleans, the deaths of more than 800 city residents, and USD 90 billion of damage across the region. This case builds on new ground as federal laws prohibit lawsuits against the COE due to failure of flooding control structures, which are one of the waterworks structures constructed and maintained by the COE across the USA. Because MRGO was created to serve as a navigation channel, federal laws do not include this provision, therefore allowing the civil case to advance for a hearing. A ruling favoring the plaintiffs (a final date for a ruling has not been established), would allow them to receive billions of dollars in damages. Furthermore, the lawsuit could set a precedent for more than 400 000 residents who have filed damage claims against the US government. Thus, the outcome of this lawsuit is of major significance not only for coastal Louisiana, but also for future US coastal policy because the legal principles presented by the lawyers for the plaintiffs could be used in making other types of claims against the federal government for Louisiana coastal wetland loss (see Section 8.07.2.1). As a result of field studies reporting on the ecological damages associated with the MRGO channel and the chronic lack of use by the navigation industry (the channel has long been considered an economic failure, only comprising 3% of shipping commerce by 1997), the COE began to develop a plan in the late 1990s to close the channel, but it was not until after Hurricane Katrina that a decision was made to implement the plan before the 2009 hurricane season at a cost of USD 24.7 million. It is estimated that the value of ecological services lost since the construction of MRGO ranged from USD 200 to 350 million. Maintenance expenditures for the MRGO (through 2002) included USD 22.1 million yr−1 for dredging and addi­ tional millions of dollars in periodic disbursement for shoreline stabilization and marsh protection projects. The MRGO case is a sobering example of current and historical complexities and consequences regarding coastal management around the world, particularly in the case of wetland loss and habitat fragmentation associated with 212 Removal of Physical Materials from Systems: Loss of Space, Area, and Habitats regional economic decisions. Indeed, this example underlines the complex interaction among natural, economic, and social issues surrounding wetland protection and conservation for more than four decades in coastal Louisiana, one of the most productive river delta regions in the world. The environmental problems caused by the MRGO were recognized since the earlier 1970s, and by the 1990s the project was widely per­ ceived as both an economic failure and a coastal hazard due to potential vulnerability to hurricanes and tropical storms (i.e., natural system). Unfortunately, the social and economic sys­ tems did not react to these potential problems until a major catastrophe struck the region resulting in major loss of life and property. This type of disconnect between the economy, the environment, and societal decision making leads to an increased level of risks associated with environmental degra­ dation as well as the direct loss of ecological services provided by wetland ecosystems. In the case of Louisiana, navigation and flood control are the historical priorities driving manage­ ment of the Mississippi River, not the sustainability of coastal ecosystems (Reed, 2009). If this is how issues of this nature are handled in the USA, one of the most developed countries in the world, what can we expect in other less wealthy/devel­ oped nations, particularly in subtropical and tropical latitudes? The case of the Grijalva–Usamacinta Delta in Mexico (discussed earlier) provides some of the current and not­so­optimistic future scenarios in managing productive coastal systems in those regions. Even among developed nations, we find different strategies to cope with wetland loss as resulting from human actions, global climate change, and natural geomorphologic con­ straints. Following Hurricane Katrina, Louisiana coastal managers and lawmakers visited the Netherlands to learn how this nation, with up to 70% of its territory below sea level, has developed large­scale hydrological advances in man­ aging flood risks by large rivers (see Section 8.07.2.1). However, the Netherlands is smaller than the Mississippi River Delta region, and densely populated with predominantly prosperous and well­educated people. In addition, the Netherlands is a rich nation with financial resources to design and manage water flows regulated through an elaborate system of canals, sluices, and pumps in a coastal zone. In the Netherlands, these areas are owned and administrated by the government in contrast to USA coastal regions where private ownership is dominant. Yet, as in the case of the Mississippi River Delta, even the Netherlands has been increasingly recog­ nizing the need for an ‘ecologicalization’ strategy to manage the coastal zone where civil engineering is giving way to ‘ecological engineering’ (Tol et al., 2003; Mitsch, 2005). Also similar to the Mississippi River Delta, water­management decisions in the Netherlands have been made on narrow economic and engi­ neering assumptions and largely biased by civil engineering concepts (Tol et al., 2003). Rivers are not just transport chan­ nels and a source of freshwater, but critical habitat and recreation areas and part of the overall ‘ecological structure’. Indeed, the current phase of dike reinforcements in the Netherlands is planned to be the last; after the year 2000, flood management has been using “natural dynamics, rather that concrete and steel” (Tol et al., 2003). A similar vision is being proposed and considered in Louisiana where recent studies suggest that sediments sup­ plied by the Mississippi River may be insufficient to rebuild and maintain the entire coast as it was historically. As a consequence, the future Louisiana coastal landscape will likely be less extensive than the present, and retreat from some areas must be expected and planned (Reed, 2009). This argument is beginning to take hold in state plans where there is an acknowledgment that coastal land loss, hurricanes, and other factors have changed the coastline, and therefore these issues and changes should be reflected in the legal definition of the coast. The Louisiana legislature has passed a joint resolution that directs the State Coastal Protection and Restoration Authority to review the current boundary of the ‘coastal area’ and possibly redraw the coastal boundary lines. This is a major departure from previous wet­ land ‘restoration’ efforts, reflecting the need to clearly define what rehabilitation and restoration mean in the context of landscape­level management of watersheds and coastal regions and their associated wetlands resources. How feasible and how fast can ‘ecologicalization’ take hold not only in developed but also in developing countries? Certainly it will require “strategic thinking, political courage, individual sacri­ fice for the greater good, and integration of land­use planning and water (Ostrom 2009) management” (Tol et al., 2003). Similar to the Netherlands case, present political, social, and economic structures in most of the coastal regions around the world are disconnected from the actual functioning of the natural environment in which they reside. As humans increasingly alter the natural landscape at regional and global scales, it is paramount to develop working strategies to observe and effectively predict how human decisions and resulting actions have and will alter ecosystems and to what degree these actions will affect socio­ecological systems (Ostrom, 2009). Acknowledgments Funding by Louisiana Department of Natural Resources (State of Louisiana) through the Coastal Louisiana Ecosystem Assessment and Restoration (CLEAR) program contributed to the prepara­ tion of this work. We want to acknowledge funding by NOAA (Award No.NA06NOS4780099), NSF (under Grant No.DBI­ 0620409 and Grant No. DEB­9910514; Florida Coastal Everglades/Long­Term Ecological Research), and the South Florida Water Management District (PO No. 4500012650) dur­ ing the last 6 years to continue our research work in the Everglades National Park and Mexico. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the authors and do not necessarily reflect the views of the National Science Foundation. Symbols and text used in Figures 6, 8, and 9 are courtesy of the Integration and Application Network (ian.umces.edu/symbols/). References Alongi, D.M., 2008. 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