Abstract
Recent declines in amphibian populations have raised concern among conservation biologists, with habitat loss and degradation due to human activities among the leading causes. The most common policies used to protect the habitat of pond-breeding amphibians are wetland regulations that safeguard the wetland itself. However, many amphibians spend much of their adult lives foraging and over-wintering in upland habitats and exist as metapopulations with dispersal among ponds. With no consideration of lands in the dispersal matrix, wetland policies may be ineffective at protecting amphibians or other wetland species that disperse across the landscape. This paper examined the adequacy and cost effectiveness of alternative conservation policies and their corresponding land use patterns on the long-term persistence of pond-breeding amphibians in exurban landscapes. We used computer simulations to compare outcomes of wetland buffer policies and broader landscape-wide conservation policies across a variety of landscape scenarios, and we conducted sensitivity analyses on the model's species parameters in order to generalize our results to other wetland species. Results showed that, in the majority of human-dominated landscapes, some amount of dispersal matrix protection is necessary for long-term species persistence. However, in landscapes with extremely low-intensity land use (e.g., low-density residential housing) and high pond density, wetland buffer policies may be all that is required. It is not always more cost effective to protect core habitat over the dispersal matrix, a common conservation practice. Conservation costs that result from forgone residential, commercial, or agricultural activities can vary substantially but increase in a nonlinear manner regardless of land use zoning. There appears to be a threshold around an average habitat patch occupancy level of 80%, after which opportunity costs rise dramatically.
Highlights
Recent declines inamphibian populations have raised concern among conservation biologists (Green 2003), with habitat loss and degradation due to human activities hypothesized to be among the leading causes (Alfordand Richards 1999).Residential and commercial development, agriculture, and forestry practices can all lower occupancy probabilities of amphibians in core habitat of breeding ponds (Guerry and Hunter 2002, Rothermel and Semlitsch 2002, Woodford and Meyer2003, Homan et al 2004,Weyrauch and Grubb 2004, Semlitsch et al 2008)
Without considering lands critical to While this study focuses on conservation of pond dispersal between ponds, breeding amphibians, the approach can be generalized wetland policies may be ineffective at protecting to other species that exist as metapopulations
Using theresultsof conservation policy analysis based on the baseline landscape of Richmond (214 habitat patches, 165-m wetland buffers, and heterogeneous land use; Fig. 1), both metapopulation size and opportunity cost increased as the level of protection increased (Fig. 2)
Summary
Recent declines inamphibian populations have raised concern among conservation biologists (Green 2003), with habitat loss and degradation due to human activities hypothesized to be among the leading causes (Alfordand Richards 1999).Residential and commercial development, agriculture, and forestry practices can all lower occupancy probabilities of amphibians in core habitat of breeding ponds (Guerry and Hunter 2002, Rothermel and Semlitsch 2002, Woodford and Meyer2003, Homan et al 2004,Weyrauch and Grubb 2004, Semlitsch et al 2008). Recent declines inamphibian populations have raised concern among conservation biologists (Green 2003), with habitat loss and degradation due to human activities hypothesized to be among the leading causes (Alfordand Richards 1999).Residential and commercial development, agriculture, and forestry practices can all lower occupancy probabilities of amphibians in core habitat of breeding ponds The most common policies used to protect pond breeding amphibians in theUnited States are state and federal wetland regulations that safeguard the wetland itself and, in some cases, a small buffer of terrestrial habitat surrounding the wetland. Many pond breeding amphibians spend much of their adult lives foraging and overwintering in upland habitats, areas not directly protected by current regulations
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