Saturday, April 24, 2010

The story of Pinta

The northernmost of the main islands of the Galapagos, Isla Pinta is isolated from civilization, but it bears scars from the hand of man nonetheless. Like most of the islands in the archipelago, in the 17th through 19th centuries Pinta was visited by pirates and whalers seeking fresh protein with a long shelf life. On Pinta they found a unique saddlebacked giant tortoise (Geochelone abingdoni) that they kept alive on their ships until they needed meat. Eventually they decimated the population, and now only one Pinta giant tortoise lives today in captivity - Lonesome George. The loss of such a large herbivore likely had severe ecological effects, but it is impossible to know conclusively as the population was effectively gone over 100 years ago.

We do know that the introduction of feral goats to the island drastically altered the ecosystem. Three goats were introduced to Pinta in the 1950s, and in just 15 years, the population had grown to 20,000 individuals. The goats decimated the plant community, and so the Galapagos National Park instituted a goat eradication program in the 1970s. By 2003, the goats were gone, and the plant community began to recover…in a strange way. With no large herbivore (neither tortoise nor goat), plants regrew rapidly to densities not seen on Pinta before. And because the goats had changed the make-up of the soil, woody shrubs regrew the fastest of all. Where before the plant community was in danger of being eaten to nothing, now it is at risk of losing species to the crowding of shrubs.

The Galapagos National Park wishes to avert that risk by reintroducing a group of giant tortoises to act as "ecological engineers". Through herbivory, seed dispersal, and the sheer force of their strong legs and heavy shells, it is conjectured that the tortoises can reshape the ecosystem into something that more closely resembles the community from a few hundred years ago. Can the tortoises do that? That's what we aim to find out!

Signing out - Elizabeth, Syracuse NY

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