chapter  9
12 Pages

Population Viability Analysis

WithMark L. Shaffer

The Northern spotted owl is a small, predatory bird native to the coniferous forests of the Pacific Northwest. Its preferred habitats are the old-growth forest communities of that region. These habitats have been extensively logged during the last century, reducing both the quantity of habitat available to this subspecies of owl and greatly increasing the fragmentation of remaining habitat. Population Viability Analysis (PVA) is intended to be a structured, systematic and comprehensive examination of the interacting factors that place a population at risk of chance extinction, especially as these relate to population size and distribution. The number of species listed as threatened or endangered is expected to grow rapidly in the coming decades, primarily because of loss of habitat. There are many habitat-limited species, such as narrowly endemic plants and some sedentary invertebrates that occur in low numbers or few sites that a PVA is superfluous.