May 30, 2013
Green Sea Turtles In Hawaii On The Road To Recovery, But Still Short Of Historic Levels
April Flowers for redOrbit.com - Your Universe Online
The Hawaiian green sea turtle population has increased since the species was listed under the US Endangered Species Act in 1978. New research from Stanford University shows, however, that the number of turtles is only a fraction of historic levels, so the calls to lift the animals´ protections may be premature.
"It's critical to compare the animal's population level to its historic abundance, not just to recent levels," said John N. "Jack" Kittinger, an early career fellow at Stanford's Center for Ocean Solutions (COS).
Kittinger, who conducted much of the research before joining COS, and his colleagues compared contemporary (1973-2012) and historical (1250-1950) nesting records of Hawaiian green sea turtles from fishery logs, archeological sites, Hawaiian-language newspapers and first-hand historical accounts. Nesting data was also collected from the green turtle field monitoring program run by NOAA's Pacific Islands Fisheries Science Center.
The team´s efforts yielded extensive data sets on the occurrence, abundance, geographic distribution and harvest of sea turtles in Hawaii spanning hundreds of years. Analyzing these data sets and other archival sources revealed that 80 percent of major historic green sea turtle nesting sites have vanished, while many others have decreased in size. Currently, 90 percent of the green sea turtle nesting in the Hawaiian Islands is at one site, which is vulnerable to sea level rise and other threats.
"Hawaiians were able to sustainably coexist with nesting green sea turtles as recently as the early 20th century, when nesting sites could still be found on the main Hawaiian Islands," said Kittinger. "After traditional harvesting restrictions gave way, we see evidence for population depletion. This needs to be considered for sustainable management of the species moving forward, including a potential harvesting program should the species be delisted."
An important cultural symbol in Hawaii, the green sea turtle also performs vital marine functions such as controlling the spread of algae in coral reefs.
"Research such as this study, based on historic and socioeconomic data, adds an important perspective that has been missing from population assessments of endangered animals," said Larry Crowder, COS science director and a sea turtle expert, who was not involved in the study. "The paper shows that Hawaii's current green sea turtle population is significantly reduced from historic levels and, due to the conservative approach of these scientists, these numbers may under represent that decline."
The findings of this study were published in a recent issue of Ecography.