Grantee Research Project Results
2004 Progress Report: Economics of Conserving Ecosystem Integrity with Residential Development around Vernal Pools
EPA Grant Number: R829384Title: Economics of Conserving Ecosystem Integrity with Residential Development around Vernal Pools
Investigators: Swallow, Stephen K. , Paton, Peter
Institution: University of Rhode Island
EPA Project Officer: Hahn, Intaek
Project Period: January 1, 2002 through December 31, 2005 (Extended to August 31, 2006)
Project Period Covered by this Report: January 1, 2004 through December 31, 2005
Project Amount: $200,017
RFA: Decision-Making and Valuation for Environmental Policy (2001) RFA Text | Recipients Lists
Research Category: Environmental Justice
Objective:
The purpose of this research project is to develop a framework for identifying and understanding the economic and ecological factors that influence society’s ability to maintain well functioning ecosystems in the face of sprawl or urban development. Particular emphasis is given to modeling the effects of residential development on amphibian metapopulations that are dependent upon vernal pools and upland habitats connecting these pools. Objectives of the research include: (1) assessing the baseline value of foregone opportunities for development and amphibian metapopulations that can be anticipated after rural residential development expands under current regulations; (2) evaluating the economic and ecological factors affecting the cost of maintaining metapopulations for an assemblage of amphibians, as represented by vernal pool ecosystems in southern New England; and (3) examining the economic and ecological implications of alternative regulatory or development incentive mechanisms that influence the probability of land development within or around vernal pool-based ecosystems.
Progress Summary:
Research during this period focused on three major work efforts: (1) refinement of the conceptual model that incorporates long-term metapopulation persistence as a safe minimum standard type constraint on residential development; (2) empirical application of the model to a case study involving pond-breeding amphibians in a Rhode Island watershed located at the rural-urban fringe; and (3) development of more robust databases for estimating heterogeneous land values and habitat quality.
Review of the theoretical biology literature identified two related constructs, developed by Illka Hanski and Otso Ovaskainen, for assessing long-term persistence of metapopulations based on spatially realistic landscape data. The metapopulation persistence capacity, similar to a single-population carrying capacity, measures a landscape’s ability to support viable metapopulations over the long term. The metapopulation size measures the average occupancy of habitat patches, reflecting the rarity or commonness of the target species throughout the landscape. Both constructs take into account the quantity and quality of habitat available, the spatial configuration of the habitat patch network, and species-specific dispersal parameters. The choice between metapopulation persistence capacity or metapopulation size in the constraint depends on the question being asked; metapopulation persistence capacity is more appropriate for examining rare and endangered species in a highly fragmented landscape, whereas metapopulation size is more appropriate for assessing the long-term persistence of a common species throughout the landscape. The conceptual model allows for both types of analyses. We expanded the metapopulation persistence capacity and metapopulation size constructs to incorporate the effects of residential development on habitat patches and the barriers to dispersal between patches and then used the revised measures as constraints within the conceptual model.
Review of the economics literature identified a combination of Von Thunen (location-oriented) and Ricardian (quality-oriented) land rents as the appropriate measure for residential development benefits. Development is assumed to have irreversible effects on the landscape. Conceptually, the model shows the opportunity costs associated with foregone development benefits that result from achieving long-term metapopulation persistence. Mathematically, the model maximizes the benefits from various developed land uses, subject to an ecological constraint that maintains the landscape’s metapopulation persistence capacity (or metapopulation size) above the safe minimum standard deemed appropriate by society. Preliminary analyses show that the opportunity costs associated with foregone development increase non-linearly with increasing probability of persistence (or increasing average occupancy). The costs of achieving the safe minimum standard increase at an increasing rate.
The conceptual model was applied to a 10,000-acre landscape containing 123 vernal pools within the Wood-Pawcatuck watershed in western Rhode Island. A ponds-as-patches approach was used to define the landscape structure. Vernal pool and other landscape data, including patch size and distance between patches obtained from the Rhode Island Geographic Information System (RIGIS), were used to generate the landscape matrix used in calculating the metapopulation persistence capacity and metapopulation size. Species-specific parameters for wood frogs (Rana sylvatica) were extrapolated from existing amphibian literature. An ordinary least squares (OLS) regression was performed on the tax assessor data gathered in the prior reporting period generating per-acre land values. A MATLAB program was developed to perform numerical optimizations based on the conceptual model described above. A series of optimizations varying the metapopulation size over its entire range produced a baseline cost function that represents the “optimal” solution. This is shown in Figure 1 as the blue line. The curve represents the tradeoff between the economic benefits of residential development and the ecological benefits of land preservation.
A number of policy scenarios (Table 1) were simulated and compared to the optimal solution. One obvious result is that it is possible to achieve a relatively high metapopulation size for a relatively minimal cost. This is attributed to the initial elimination of small isolated patches and large “empty” spaces between patches. A second key result is that current policies, which only protect the wetland or a small buffer around the wetland, result in long-term metapopulation extinction (they fall to the far left off the graph in Figure 1). Alternative policies that protect larger buffers or some of the intervening landscape matrix perform better, but still do not achieve the optimal solution. Market-based policy alternatives, such as impact fees or transferable development rights, may be required.
Figure 1. Comparison of the Opportunity Costs Associated With Foregone Development Corresponding to Various Conservation-Oriented Policy Alternatives (policy alternatives are listed in Table 1)
The land allocation framework presented above is simplistic in terms of homogeneity of land values and habitat quality. To provide for a more robust analysis, additional GIS data were generated that included a variety of parcel-level characteristics (e.g., slope, soils, elevation, distance to town center, distance to highway, quantity of neighborhood open space, distance to major employment centers, etc.). These data will be combined with tax assessor data to estimate heterogeneous land values. The egg-mass count database created in the prior reporting period will be used to identify heterogeneity of habitat quality.
The preliminary analysis treated the land between patches as one contiguous “swiss cheese” land area. To accommodate different land uses in a more robust model, the intervening landscape has been divided into “neighborhoods” based on current zoning districts. These neighborhoods will allow for assessment of a wider range of policy alternatives. In addition, the 10,000-acre parcel landscape matrix was expanded to encompass an entire town within the Wood-Pawcatuck watershed. This new landscape matrix uses patch areas, two different buffer sizes, distances between patches, percent of distances in each of 16 neighborhoods, existing development densities in each patch and each neighborhood, and patch qualities for 214 vernal pools distributed across 25,000 acres. One difficulty encountered in the preliminary analysis was the allocation of upland habitat to individual ponds when ponds were tightly clustered. Based on review of the amphibian literature and discussions with amphibian ecologists, it was decided to treat pond clusters (i.e., ponds within 100 m of each other) as a single habitat patch.
Table 1. Descriptions of Policy Alternatives
Policy Alternative |
Description 1 |
Current 1 (C1) |
Current wetland policy that protects the area of the pool only |
Current 2 (C2) |
Same as C1 except developed parcels are two acres |
Envelope (E) |
Protect vernal pool plus 100-foot buffer (envelope) |
Guidelines (G) |
Protect vernal pool plus 100-foot buffer plus 75% of critical habitat;2 recommended vernal pool guidelines3 |
New Policy 1 (P1) |
Protect vernal pool plus 100-foot buffer plus 50% of critical habitat |
New Policy 2 (P2) |
Protect vernal pool plus 100-foot buffer plus 25% of critical habitat |
New Policy 3 (P3) |
Protect vernal pool plus 100-foot buffer plus 25% of critical habitat plus 25% of intervening landscape matrix |
No Development (0) |
Protect all vernal pools plus 100-foot buffer plus 100% critical habitat plus 100% of intervening landscape |
1 Unless otherwise noted, all policies assumed all developed parcels were one acre. 2 Critical habitat is defined as an outer buffer 100-750 feet from pool edge. 3 Vernal pool guidelines (described in Calhoun and Klemens 2002). |
Future Activities:
The analytical model will be expanded to incorporate a more robust implementation of the metapopulation persistence capacity constraint. Patch “effective area” and dispersal barrier functions will include non-linear development threshold effects rather than a simple linear relationship. Different types of development will be allowed. This revised conceptual model will be used in two ways. First, an expanded heterogeneous empirical application using the Rhode Island GIS data gathered above will be conducted. Each of the policy scenarios described in Table 1 will be re-analyzed with the new data set and modified functions. Results are expected to provide decisionmakers with detailed information on the effectiveness of current and proposed wetland policies in their ability to protect wetland species over the long term. Additional policies, such as TDR (transferable development rights) programs, will be examined to determine if current zoning regulations can be modified to achieve higher amphibian persistence at a lower cost within the Wood-Pawcatuck watershed.
The preliminary empirical application identified several key parameters driving the system. These include pond (patch) density, development density, development intensity, species-specific dispersal distance, and species-specific extinction, immigration, and emigration rates. A simulation program of a stylized town based on the actual towns in the Wood-Pawcatuck watershed will be developed to perform sensitivity analysis on the key variables. For example, pond densities range from less than 2 ponds to more than 10 ponds per square kilometer in the watershed, and residential development densities range from 1 house per 20 acres to 5 houses per 1 acre. Amphibian dispersal distances range from less than 400 m to greater than 1000 m. The simulation program also will allow for more detailed examination of the relationships between economic and ecological variables. For example, the landscape consists of both high and low quality habitat as well as high and low quality development parcels. Parcels attractive for development may or may not coincide with high quality habitat patches. The simulation program will allow for analyses of all possible combinations, making insights gained more transferable to regions outside Rhode Island. It is anticipated that results from both these activities will be presented at appropriate economic and ecology conferences and submitted for peer-reviewed publication.
Journal Articles on this Report : 4 Displayed | Download in RIS Format
Other project views: | All 26 publications | 11 publications in selected types | All 7 journal articles |
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Type | Citation | ||
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Egan RS, Paton PWC. Within-pond parameters affecting oviposition by wood frogs and spotted salamanders. Wetlands 2004;24(1):1-13. |
R829384 (2002) R829384 (2003) R829384 (2004) R829384 (Final) |
Exit Exit |
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Montieth KE, Paton PWC. Emigration behavior of spotted salamanders on golf courses in Southern Rhode Island. Journal of Herpetology 2006;40(2):195-205. |
R829384 (2004) R829384 (Final) |
Exit Exit |
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Paton PWC, Egan RS, Osenkowski JE, Raithel CJ, Brooks RT. Rana sylvatica (wood frog) breeding behavior during drought. Herpetological Review 2003;34(3):236-237. |
R829384 (2003) R829384 (2004) R829384 (Final) |
not available |
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Paton PWC. A review of vertebrate community composition in seasonal forest pools of the northeastern United States. Wetlands Ecology and Management 2005;13(3):235-246. |
R829384 (2004) R829384 (Final) |
Exit Exit |
Supplemental Keywords:
wetlands, vernal pool ecosystems, pond clusters, residential development, urban sprawl, amphibian metapopulations, metapopulation persistence capacity, metapopulation size,, RFA, Economic, Social, & Behavioral Science Research Program, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Ecosystem/Assessment/Indicators, Ecosystem Protection, Economics, decision-making, Ecology and Ecosystems, Economics & Decision Making, Social Science, ecological exposure, ecosystem integrity, vernal pool ecosystems, decision making, wetland regulation, cost-effective ecosystem protection, environmental values, environmental policy, residential development, ecosystem integrity and residential development, vernal pools, community-based, conservation biology, public policy, cost-effective ecosysem protection, conserving ecosystem integrityProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.