Extinction of species has occurred as a natural process since life began on Earth, but human activities have greatly accelerated the rate of extinction in recent years. Among the many factors that may contribute to the disappearance of a species are habitat destruction, over-exploitation, introduction of exotic species, and climate change. Endangered animals face extinction in all or a part of their ranges unless specific measures are taken for their protection. Threatened animals are likely to become endangered in the foreseeable future. Endangered mammals and birds have received the greatest amount of attention in conservation efforts to date, but there is a growing recognition of the importance of endangered amphibians, reptiles, fish, and invertebrates, so these animals are likely to receive more attention in the future. Although plants are absolutely essential to human and animal life, endangered plants have received relatively little attention compared with that given to endangered animals.
This guide is intended to serve a wide research audience, as well as to provide useful, quality information and research assistance to the interested public. This guide is not an exhaustive list of resources, but rather a starting point for researching endangered and threatened species.