Goats and other exotic herbivores (including pigs and burrows) are frequently "ecological dominants" which can alter an ecosystem completely. Feral herbivores can totally strip areas by foraging, resulting in severe erosion and subsequent loss of native trees which die due to lack of soil. One example of such destruction occurs in the Galapagos, on the island of Santiago, where the dense forests provide water to the whole system by dripping fog collected by the trees. As goats destroy this vegetation, the entire ecosystem is destroyed. On Aldabra atoll, endangered tortoises are threatened by goats. And on Hawaii, pigs are dangerous invaders and need to be eliminated to protect the natural ecosystem.
Bruce Coblenz believes that in this country, efforts to control exotic species are often complicated by animal-protection groups that don't want animals destroyed -- even invaders that are destroying native ecosystems.