Taskbarx free alternative6/4/2023 ![]() The endangered Fender's blue butterfly ( Icaricia icarioides) was recently assessed with a goal of providing additional information to the United States Fish and Wildlife Service, which was developing a recovery plan for the species. The use of PVA increased dramatically in the late 1980s and early 1990s following advances in personal computers and software packages. In 1986, Gilpin and Soulé broadened the PVA definition to include the interactive forces that affect the viability of a population, including genetics. ![]() PVA gained popularity in the United States as federal agencies and ecologists required methods to evaluate the risk of extinction and possible outcomes of management decisions, particularly in accordance with the Endangered Species Act of 1973, and the National Forest Management Act of 1976. In 1978, Mark Shaffer proposed a model for the grizzlies that incorporated random variability, and calculated extinction probabilities and minimum viable population size. In the 1970s, Yellowstone National Park was the centre of a heated debate over different proposals to manage the park’s problem grizzly bears ( Ursus arctos). ( April 2016) ( Learn how and when to remove this template message) ![]() Unsourced material may be challenged and removed. Please help improve this section by adding citations to reliable sources. ![]()
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