Threatened species are very likely to become endangered in the near future unless they or their habitats are fully protected and managed. Species of special concern may become threatened unless protective management strategies are employed. Since the early 1970s, these legal classifications have been used to help protect species and their habitats that are in greatest jeopardy. By far the most common cause of declines in wildlife numbers is habitat loss or alteration due to human activities. Many species that have not gone through the formal listing process were determined by GFC to be in just as much jeopardy of extinction as those species already listed.
Extinction is a process that occurs over a long period.
When an essential habitat component is diminished to a level insufficient for a species' survival, that species becomes extinct in that area. Species first become extinct on individual sites, then extinction spreads to township, county, state, national, and global levels. See Figure 1 . Tables Table 1. For information on obtaining other extension publications, contact your county Cooperative Extension Service office.