Development of ecologically meaningful, multiple-species conservation strategies under the California and U.S. Endangered Species Acts

The California and U.S. Endangered Species Acts prohibit take of protected species, but allow for authorization of take incidental to otherwise lawful activities provided the take is minimized and mitigated. Incomplete and inconsistent ecological information can limit the contribution of mitigation plans for incidental take, especially those for multiple species, to species persistence. Many such plans focus on acquisition and management of coarse-resolution land-cover or land-use types. These classifications may not coincide with a species’ resource requirements (its habitat) or the greatest constraints to its viability. Complementing acquisition with rigorous research on population biology, stressors, and habitat use and quality may be much more effective than preservation of putative but unproven habitat. Such adaptive conservation can be applied to species with restricted or extensive distributions. When the distribution and ecology of geographically restricted species are well-known, then connectivity analyses, sometimes complemented by spatially explicit, mechanistic population models, may inform habitat acquisition and management. When little information exists on the ecology or vital rates of a restricted species, we suggest assessment of occupancy, habitat use, or demography; tracking individuals’ movements; and evaluation of habitat quality. Acquisition and management of local lands that may not serve as habitat is unlikely to contribute to conservation of extensively distributed species with range-wide declines. Instead, we suggest that conservation efforts for these species emphasize strategic acquisition of open space (large, undeveloped areas that are more likely to serve as high-quality habitat), potentially in locations distant from the permit area. The above areas of research can inform optimization of conservation locations. Many mitigation decisions are based on assumptions drawn from limited data. Inclusion of scientific research in development and implementation of mitigation plans for incidental take can strengthen the plans’ information content, improve the ecological success acquisition and management, and advance conservation of protected species.