Giant tortoises on island ecosystems are ecological engineers whose decline and recovery have profound effects on island biodiversity.
Tortoises killed by introduced predators and hunters suffered direct harm, while survivors experienced reduced reproductive success and the slow ecological degradation of their island homes. Captive-bred tortoises released for conservation face adjustment challenges in restored habitats. Tortoises in poor zoos and private collections face inadequate temperature regulation, nutrition, and space that causes chronic health problems. The ecological restoration of islands benefits thousands of species beyond the tortoises themselves, improving welfare at an ecosystem level. Long-lived tortoises hold generations of environmental knowledge that supports their survival.