In the 1960s, giant tortoises on the Galapagos island of Espanola were on the brink of extinction, but now according to a recent study there are enough turtles on the island to survive on their own.

James Gibbs, a conservation biology professor at the State University of New York College of Environmental Science and Forestry, is the lead author of the study, which was published on Oct. 28 in the journal PLOS ONE. The study chronicled a 40-year project headed by the Galapagos National Park Service that attempted to save the Espanola tortoises by breeding them in captivity and rereleasing them onto the island.

“This particular study was important to document that we can also correct our mistakes and recover and rebuild,” Gibbs said. “These species can be recovered from the brink of extinction … it’s really important for species like this that are system engineers. They’re not just intrinsically interesting. They do very important things in the environment and so it’s important to recover them, not just the right thing to do.”

Two thousand tortoises were re-released onto the island in 1975, but Gibbs only got involved in 1994. He and his team analyzed data from the National Park Service and found that only half of those tortoises remain today. This number is still enough to ensure that humans can remove themselves from the conservation process and allow the tortoises to thrive on their own.

Johannah Barry, president of the Galapagos Conservancy, said the success of the organization’s work is due to its observations of the Galapagos Island as a whole.

“So we’re looking at plants and animal interactions, we’re looking at soil composition, we’re looking at all of the things that add up to make the survival of, let’s say, a charismatic species like the giant tortoise successful,” Barry said.

Gibbs agreed that one of the things that made this project unique was the emphasis on the ecosystem as a whole. He added that the ecosystem still has a long way to go.

“Forty years might sound like a long time, but it’s a wink of an eye relative to the centuries its going to take for the tortoises then to bring this ecosystem back into shape and to restore it,” Gibbs said.

Part of the reason the ecosystem is so depleted is because sailors introduced goats to the island in the 1800s. These goats destroyed the native vegetation that the tortoises relied on for food, leading to the tortoises near extinction and a shift in the composition of the island’s ecosystem. The tortoises could not have been re-introduced without the effort to exterminate the goat population that was completed in the 1990s.

“There’s an aspect of conservation that’s not elegant, not glamorous, that the public often doesn’t want to know about, but there’s really no choice — either tortoises or goats,” Gibbs said.

Susan Parks, a biology professor at SU, said that because human intervention endangered the giant tortoises, the project’s repopulation of a major species on an island is a good sign of progress.

In fact, because of the success of the Espanola experiment, scientists hope to introduce Espanola tortoises onto other islands with extinct populations that were similar to the Espanola species. In a few months, scientists will release 200 Espanola tortoises onto the island of Santa Fe. Similar projects will be carried out on other islands in coming years.

“There’s not many examples where we can actually recover a species to the point of simply being able to stop helping them, but that’s the case here,” Gibbs said. “We can step out of the picture, but I think it is relevant and I think it’s possible to do other places.”

Published on November 4, 2014 at 12:01 am

Contact: clmoran@syr.edu