In recent months, we have read numerous articles in The Times concerning the removal of feral goats from San Clemente Island. As biologists who have visited the island and directly observed the impact of goats on the vegetation, we would like to discuss the situation from an ecological viewpoint rather than one focused only on the goats or how they are removed.
Islands are isolated environments that are especially conducive to the evolution of species of plants and animals. In many cases, island endemics are incapable of coexisting with species from mainland habitats. The practice of introducing prolific, herbivorous mammals like goats has been an ecological disaster for many islands. As goats rapidly multiply, they destroy the vegetative structure of an island and drive sensitive species of plants, as well as animals that depend on that structure, to extinction.
This pattern can be seen, in varying degrees, on many of the Channel Islands. The situation on San Clemente is much worse. Upper portions of the island have been reduced to grassland, and the slopes to cactus and scrubland. Regeneration of trees and other woody vegetation has all but been eliminated.
Despite the massive ecological damage by goats, San Clemente still has the greatest number of endemic plant and animal species of all the California Channel Islands. Six species occurring only on San Clemente Island are named as endangered or threatened by the federal Endangered Species Act of 1973. Another 11 species are candidates because of their precarious status. There is no scientific dispute that these species face possible extinction as a result of ecological damage from the feral goats.