Two years ago, at the estimated age of one hundred, Lonesome George died — a giant tortoise from Pinta Island. His name was no accident: the animal was the last surviving specimen of his species, known as Chelonoidis abingdonii. The anniversary of this species' extinction is an occasion to focus attention on the rapid decline being suffered by many tortoise species, among the animals disappearing most quickly.

From the moment of his discovery, which dates back to 1972, Lonesome George was always the last of his kind and became a symbol of the fight for conservation. The Pinta Island tortoises, a subspecies of the Galápagos tortoise, were wiped out by hunting and by the introduction of goats onto their island, which competed with the tortoises for food.

Tortoises belong to an ancient animal class and first appeared on the planet more than two hundred million years ago. These creatures have therefore witnessed a great deal and have survived climate upheavals, ice ages and mass extinctions. Yet today almost half of the more than three hundred existing species are at risk of disappearing. The main threats are habitat destruction, hunting (both for meat and for the shell) and the illegal trade in exotic animals.

A further complication for tortoises is a factor linked to their reproduction. In most tortoise species, sex is determined not by genes but by incubation temperature. The survival of the leatherback sea turtle (Dermochelys coriacea Vandelli), for example — the largest turtle in the world and among the most endangered — is threatened by ocean warming, which would unilaterally skew the sex of offspring.

The Galápagos tortoises (Chelonoidis niger) came close to disappearing forever because of humans. For centuries they were eaten by sailors passing through that archipelago. By 1974 the population had plummeted from around 250,000 individuals to just 3,000. Thanks to conservation efforts the species has recovered and today nearly 20,000 specimens are counted. One subspecies in particular, living on a nearby island — the Española tortoise — has been the protagonist of a spectacular demographic recovery, growing from 14 specimens in 1970 to the current 860.