( Current conservation assessments of end...)All the eggs in one basket

Current conservation assessments of endangered Caribbean sea turtles are too optimistic, according to Loren McClenachan and colleagues from the Scripps Institution of Oceanography. McClenachan, Jeremy Jackson and Marah Newman agree that conservation efforts since the 1970's have dramatically helped increase green and hawksbill turtle populations that nest on protected beaches. However, they argue that dwindling turtle populations on many historically important nesting beaches are overlooked by conservation assessments that focus instead on the few large nesting sites that remain. The study, "Conservation implications of historic sea turtle nesting beach loss," appears in the August issue of Frontiers in Ecology and the Environment.

The researchers present the first maps of historical nesting populations

Hunted for hundreds of years for food and for decorative purposes, turtle populations were greatly reduced by people. Using trade records from 163 historic sources in four time periods in 20 Caribbean regions, McClenachan and colleagues mapped the historic nesting areas of green and hawksbill turtles, and used density descriptions and harvest data to categorize "major" and "minor" nesting sites.

Historically, large nesting populations existed throughout the Caribbean. The researchers estimated 59 nesting sites existed for the green turtles, and 55 sites existed for the hawksbill turtles. Based on their results, 20 percent of historic nesting sites have been lost entirely due to land development and turtle exploitation, and another 50 percent of the remaining sites have been reduced to dangerously low populations.

"The loss of even a single nesting site makes a permanent, irreversible dent in the sea turtle population," says McClenachan.

The scientists estimate that today's current population of 300,000 turtles once was as large as 6.5 million adult turtles in the Cayman Islands in the 17th Century, with close to
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Source:Ecological Society of America

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