Endangered ecosystems of the United States: a preliminary assessment of loss and degradation
This report estimates declines of natural ecosystems in the United States, provides a rationale for ecosystem-level conservation, discusses decline and threat as criteria for conservation, and relates ecosystem losses to endangerment at species and population levels. Ecosystems are defined generally and at various spatial scales and include vegetation types, plant associations, natural communities, and habitats defined by floristics, structure, age, geography, condition, and other ecologically relevant factors. The methodology for this report consisted of a literature review and a survey of conservation agencies and professionals. The results of this preliminary study indicted significant losses of biodiversity at the ecosystem level in the United States. The most substantial losses were summarized by listing ecosystems as critically endangered, endangered, and threatened. More than 30 critically endangered, 58 endangered, and more than 38 threatened ecosystems were identified. Losses of all kinds of ecosystems have been most pronounced in the South, Northeast, and Midwest, and in California.