Relating Conservation Goals To Ecological Outcomes

To protect the Earth’s loss of biodiversity, conservation biologists use tools to help increase endangered plant and animal population sizes. Although goals are often set for population sizes, the lack of information for many species makes setting goals difficult. A recently proposed framework has suggested goals should instead be set for the desired results of species conservation and then related back to population size and growth. In order to be broadly applicable, this framework considers populations to follow a classic logistic model of growth. Here we examined information on twenty endangered mammal species protected by the Endangered Species Act to assess how current goals relate to population predictions from logistic growth models. We recorded population histories, conservation tools used, and goals set from the U.S Fish and Wildlife Service and National Oceanic and Atmospheric Association. We constructed population growth graphs to determine if populations showed signs of density-dependent regulation and predicted carrying capacities to assess if goals were feasible. We also examined the relationship between population goals and extinction probability. Results suggest goals may be unachievable for some species and that lower goals may be both more feasible and not lead to increased risks of extinction. Furthermore, we suggest how conservation tools should be considered in their relation to changing basic population growth parameters. These results offer a method for reassessing goals using information from early in conservation projects and suggest that adaptive management strategies could be used for setting more appropriate goals.