• Rory Carroll, Latin America correspondent
• The Observer, Sunday 27 June 2010
• Article history

Scientists have successfully reintroduced giant tortoises to a Galápagos island where the species once teetered on extinction, raising conservation hopes for the rest of the archipelago.

A survey of Española, the southernmost island, confirmed last week that a pioneering effort to repatriate giant tortoise hatchlings has produced a thriving, reproducing population of more than 1,500 specimens. The project aims to turn the clock back to before human beings all but wiped out a species that helped to inspire Charles Darwin's theories on evolution and natural selection. "It's a great end to a sad story," said Johannah Barry, president of Galápagos Conservancy, a Virginia-based organisation which partly funded the study.

Preliminary results of the survey, conducted over 10 days by 24 wardens from the Galápagos national park authority, found that albatross, cactus and woody vegetation had also partly recovered, restoring the island to something akin to what Darwin saw two centuries ago.

A giant tortoise (Geochelone hoodensis) population which in the 1970s had dropped to about 15 was once again a common sight on the island, said Washington Tapia, a park official who led the survey, which used electronic devices to track the animals. "During the expedition we found nests, recently hatched tortoises, and adults born on Española, which indicates that the tortoise population is doing well."

The population now numbered between 1,500 to 2,000, said Linda Cayot, a scientific adviser to Galápagos Conservancy. "We will have a much better idea when the survey results are compiled." The original population was thought to number up to 5,000 before becoming a vulnerable source of fresh meat for passing sailors.

The project's success has bolstered a plan to "re-tortoise" another island, Pinta, with the same species in the hope of re-creating a "pre-human" balanced ecosystem. The scattering of rocky, volcanic islands 600 miles west of mainland Ecuador are a Unesco world natural heritage site and home to dozens of endemic species found nowhere else. Some 95%  of the territory's 3,000 sq miles is a protected area.

"It's completely amazing, one of the few places where you can actually see evolution happening in real time," said Henry Nicholls, ambassador for the Galápagos Conservation Trust. He welcomed the recovery of Española's giant tortoise population. "They are a flagship species which capture the public imagination."

For much of the 20th century the archipelago was a symbol of human destruction. After sailors ran out of tortoises to eat, they introduced goats to several islands. From numbering just a handful the new arrivals multiplied into thousands, then tens of thousands. They stripped vegetation and made the islands uninhabitable for the few remaining tortoises and other endemic species.