Papers by Dexter Salinas Ontoy
Biodiversity Journal, Sep 2014
A new Importance-Diversity Index is proposed as an enhancement to the traditional Shannon’s diver... more A new Importance-Diversity Index is proposed as an enhancement to the traditional Shannon’s diversity index. The proposed index incorporates an importance weight to each species of organisms found in an ecosystem. The importance weights are derived from four (4) main domains deemed important in conservation biology, namely: (1) Species endemicity, (2) Economic utility, (3) Functional role in the ecosystem, and (4) Risk status of the species (threatened or endangered). Scenario simulations show that the new index aids in conservation decisions particularly in cases where the Shannon’s indices of the ecosystems are equal or near equal or even in situations where the Shannon’s index clearly identifies a site but the relative importance of the species found in other sites are heavier.
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University of the Philippines in the Visayas (UPV Journal of Natural Sciences, Jun 2005
The mangrove forest in four sampling sites in Ormoc Bay, namely; Benabaye, Calunagan, Puerto Bell... more The mangrove forest in four sampling sites in Ormoc Bay, namely; Benabaye, Calunagan, Puerto Bello and Tahusan Islet, was reassessed ten years after the implementation of the Fisheries Sector Program. The density ha-1 and the species diversity decreased by 50% or more; in addition, the basal areas were greatly reduced indicating that there was excessive harvesting of large mangrove trees since 1992. More than 50% of the different mangrove genera exhibited high regenerative capacities. Avicennia and Rhizophora have high regenerative capacities in all sampling sites; in contrast the regenerative capacities of Nypa and Sonneratia in four, of Ceprios in three and of Aegiceras and Bruguiera in two sampling sites were way below 50%. The mangroves in all sampling sites do not exhibit a distinct species zonation pattern; almost all the species overlap with each other.
The mangrove forest is highly utilized by the local communities. People gather different mangrove species and a variety of edible invertebrates both for household consumption and for economic gains by selling them to the market. The resource, however, is seriously threatened by human-induced stresses, such as, over-exploitation, conversion of mangrove areas to fishponds, and soil erosion due to the denuded forest cover in the uplands. Recommendations to prevent further degradation of the mangrove resource are given.
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submitted and under evaluation
The value of services, commodities or goods which are not traded in the market are currently appr... more The value of services, commodities or goods which are not traded in the market are currently approximated using either “Willingness to Pay” (WTP) or “Willingness to Accept Compensation" (WTA). These concepts figure prominently in contingent valuation or stated preference models in economics. Simply put, the buyer’s WTP needs to reach the seller’s WTA in order for a successful transaction to occur. This situation still persists in rural Philippines where haggling for a price of a commodity has become an art for small traders. This paper provides mathematical models for valuing non-traded resources such as functional marine reserves. The deterministic model defines a negotiation domain in terms of the underlying utility (u) of the resource. The WTA and the WTP are expressed as bounded, monotonically increasing continuous functions of u. The stochastic model defines the negotiation domain in terms of the assumed random WTA and WTP values from a Gumbel distribution. The paper also introduces a technique for approximating the value of the resource in question through the intersection of the confidence intervals constructed for both average WTA and WTP. A Monte Carlo simulation is provided to concretise the concepts developed in the case of marine reserves.
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This study challenges the concept of ‘spill-over effect’ which is being used as theoretical found... more This study challenges the concept of ‘spill-over effect’ which is being used as theoretical foundation in MPA establishment that would guarantee improved fish catch and henceforth the welfare of the households. Given their socio-economic characteristics, small-scale fishing communities are still the most vulnerable sector in the country.The use of multiple indicators was done to capture the different dimensions of the living standard and poverty. The main data gathering method employed in this study was the household survey.
The communities’ level of acceptance influenced MPA's extent of management and enforcement to reach level 4. The variance in the household income were neutralized by the households’ total expenditures and family size. Body mass index of households fall within the normal range, regardless of total household income, household expenditures or family size. Low income did not necessarily result into low BMI of fishing households. The community expressed concerns on the establishment of MPA in their area. Generally, they expressed that their fish catch has dwindled over the years even with the presence of the MPA.
The results of this study show that effective MPA enforcement and management do not guarantee improved human welfare. In this regard, other interventions are still necessary to supplement MPA establishment, management and enforcement as a strategy in addressing poverty in the countryside, specifically the small-scale fishing communities.
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The Hardy-Weinberg Equilibrium model was used as a platform for analyzing a field survey data on ... more The Hardy-Weinberg Equilibrium model was used as a platform for analyzing a field survey data on the distribution of mangrove species in two is lets of Eastern Visayas, Tabuk and Cabgan. The study is part of a larger Island Biodiversity program of the Cebu Normal University. A new estimator, developed by the first author, for measuring deviations from equilibrium was used in the study, while the relationship between the classical Shannon’s diversity index and the Hardy-Weinberg equilibrium was likewise explored. Results revealed that the probability of extinction of the mangrove species in both islands are relatively high and the most probable future configuration of these species, apart from a total extinction scenario, is either a single-species ora two-species configuration. The protection of the Tabukislet yielded positive benefits for the diversity of the mangrove species, while a reforestation project for the two islands served to reduce heterogeneity viz. reduce diversity, because only one or two species of mangroves were planted in the early part of 2000.
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"Very recent research (Felipe and Porio, 2010) revealed no direct relationship between the length... more "Very recent research (Felipe and Porio, 2010) revealed no direct relationship between the lengths of basic education cycles and student performance in TIMSS (2007) science and mathematics tests. The TIMSS scores were impliedly used as proxy measures of quality for basic education. The present study is an in-depth analysis of the various socio-economic factors that directly bear on the quality of basic education outcomes using the sub-indices of the Global Economic Index (GCI) 2009 in view of the assertion that a mechanical addition of more years in basic education does not improve quality at that level. Results revealed that specific basic economic parameters (connectivity and access) related to poverty reduction, efficient and effective higher education and training of teachers, technological readiness and strengthening of economic fundamentals all significantly bear on the quality of basic education globally.
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Two optimizations models are explored: one that maximizes a social welfare – function subject to ... more Two optimizations models are explored: one that maximizes a social welfare – function subject to biological diversity and management constraints, which maximizes biodiversity subject to management resource constraints and social welfare considerations are proposed to determine sizes of Marine Protected Areas (MPA). The models are applied to the marine protected areas in the Visayas, Philippines using available records in the Directory of Marine Protected Areas in the Visayas by fitting the species-area relation (SAR) curve, the management resource–area curve (MRA), and the welfare–area (WA) curve from each of the marine protected areas listed. A comparison of the optimal MPA sizes computed from the model and the prevailing MPA sizes in the Visayas area revealed that non–functional MPA shave sizes which do not support either the management resource, biodiversity requirement or social–welfare considerations.
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The interaction of multiple species of animals inan ecological system is modeled by first reducin... more The interaction of multiple species of animals inan ecological system is modeled by first reducing the ecologicalsystem to a kernel ecological system consisting of keystonespecies and top predators in the environment through GraphTheory. From the reduced kernel ecological system of keystonespecies, a system of Lotka-Volterra differential equations isused to describe the predator-prey relationships that exist. Theequations for the number of organism per species were derivedand additive environmental stochasticity or noise is added toeach equation. The noise is assumed to come from an extremevalue distribution or Gumbel distribution to reflect the impactof extreme weather conditions on the population dynamics ofthe entire ecological system. Results reveal a rich dynamicalbehavior for the system which otherwise would not have beenrevealed by straight application of deterministic predator-preymodels
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The estimation of the reproduction number of dengue viral transmission is an active area of resea... more The estimation of the reproduction number of dengue viral transmission is an active area of research owing to the importance of the reproduction number as an epidemiological quantity. It determines, among others, the intensity of intervention and control measures necessary to contain an outbreak. This study uses the reproduction number proposed by Favier, Degallier, Rosa-Freitas, Boulanger, Costa Lima, Luitgards-Moura, Menkes, Mondet, Oliveira, Weimann, & Tsouris (2006) but employs a Bayesian estimation procedure to estimate the parameters found in the reproduction number. Earlier studies by Chowell, Rivas, Smith, & Hyman (2006) showed that reproduction numbers computed from this basic formula overestimates the viral transmissibility and hence, also overestimates the control mechanisms employed to control the outbreak. The present study essentially deflates the reproduction number by the prior distribution of the parameters in a Bayesian viewpoint. The new estimation procedure is tried out for selected cases in Central Visayas and Bukidnon where outbreaks of dengue cases were noted for 2010.
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國際文化研究: 真理大學通識教育學報, Jan 1, 2011
On Indonesia's East Timor and Aceh cases, ASEAN diplomacy has been consistent with its norm of no... more On Indonesia's East Timor and Aceh cases, ASEAN diplomacy has been consistent with its norm of non-interference. Collectively, ASEAN consistently rallied behind Indonesia in both cases. Within the ASEAN membership, however, member states were divided in the case of East Timor and unanimous in the case of Aceh. The divisiveness within the ASEAN in the case of the former and its unanimity in the case of the latter were influenced by the compounded effects of three factors: international support caused by the media coverage of human rights violations in East Timor, the normative shift that occurred at the global level, and the occurrence of the 1997 Asian financial crisis.
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Papers by Dexter Salinas Ontoy
The mangrove forest is highly utilized by the local communities. People gather different mangrove species and a variety of edible invertebrates both for household consumption and for economic gains by selling them to the market. The resource, however, is seriously threatened by human-induced stresses, such as, over-exploitation, conversion of mangrove areas to fishponds, and soil erosion due to the denuded forest cover in the uplands. Recommendations to prevent further degradation of the mangrove resource are given.
The communities’ level of acceptance influenced MPA's extent of management and enforcement to reach level 4. The variance in the household income were neutralized by the households’ total expenditures and family size. Body mass index of households fall within the normal range, regardless of total household income, household expenditures or family size. Low income did not necessarily result into low BMI of fishing households. The community expressed concerns on the establishment of MPA in their area. Generally, they expressed that their fish catch has dwindled over the years even with the presence of the MPA.
The results of this study show that effective MPA enforcement and management do not guarantee improved human welfare. In this regard, other interventions are still necessary to supplement MPA establishment, management and enforcement as a strategy in addressing poverty in the countryside, specifically the small-scale fishing communities.
"
The mangrove forest is highly utilized by the local communities. People gather different mangrove species and a variety of edible invertebrates both for household consumption and for economic gains by selling them to the market. The resource, however, is seriously threatened by human-induced stresses, such as, over-exploitation, conversion of mangrove areas to fishponds, and soil erosion due to the denuded forest cover in the uplands. Recommendations to prevent further degradation of the mangrove resource are given.
The communities’ level of acceptance influenced MPA's extent of management and enforcement to reach level 4. The variance in the household income were neutralized by the households’ total expenditures and family size. Body mass index of households fall within the normal range, regardless of total household income, household expenditures or family size. Low income did not necessarily result into low BMI of fishing households. The community expressed concerns on the establishment of MPA in their area. Generally, they expressed that their fish catch has dwindled over the years even with the presence of the MPA.
The results of this study show that effective MPA enforcement and management do not guarantee improved human welfare. In this regard, other interventions are still necessary to supplement MPA establishment, management and enforcement as a strategy in addressing poverty in the countryside, specifically the small-scale fishing communities.
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