Formed over many centuries by volcanic activity, Hawaii's topography—and therefore its flora and fauna—have been subject to constant and rapid change. Relatively few indigenous trees remain; most of the exotic trees and fruit plants have been introduced since the early 19th century. Of 2,200 species and subspecies of flora, more than half are endangered, threatened, or extinct. As of August 2003, 273 plant species were listed as endangered or threatened by the US Fish and Wildlife Service.
The only land mammal native to the islands is the Hawaiian hoary bat, now endangered; there are no indigenous snakes. The endangered humpback whale migrates to Hawaiian waters in winter; other marine animals abound. Among the 44 animal species listed as endangered or threatened as of August 2003 were four species of sea turtle and humpback whale. Among threatened birds are several varieties of honeycreeper, short-tailed albatross, Hawaiian coot, and the Hawaiian goose (nene). The nene (the state bird), once close to extinction, now numbers in the hundreds and is on the increase. Animals considered endangered by the state but not on the federal list include the Hawaiian storm petrel, Hawaiian owl, Maui 'amakihi (Loxops virens wilsoni), and 'i'iwi (Vestiaria coccinea).