Palmyra Atoll: An Island Paradise In Recovery
It shares the name of a James Bond villain's gorgeous island lair, and it, too, is stocked with lush palm trees and marauding sharks. But at the Palmyra Atoll National Wildlife Refuge—a tropical island system in the remote reaches of the Pacific Ocean—it's the palm trees that are threatening and the sharks that are being protected.
U.S. Geological Survey (USGS) Western Ecological Research Center (WERC) biologists are part of the Palmyra Atoll Research Consortium, a partnership of scientists and institutions studying the forests and waters of this U.S. territory. In the 1940s, Palmyra Atoll served as a U.S. military outpost, and now Palmyra faces challenges from past habitat impacts and present concerns about invasive species and sea-level rise.
A Not-So-Lovely Bunch of Coconuts
A USGS report released in January 2011 and authored by WERC scientists Stacie Hathaway, Kathryn McEachern, and Robert Fisher recommends habitat-management strategies for Palmyra. (See Terrestrial Forest Management Plan for Palmyra Atoll, USGS Open-File Report 2011-1007) One finding casts the coconut palm in a villainous role.
Coconut palms, a species once farmed in local plantations, are taking over the island landscape and driving out a rare, native tree species, Pisonia grandis, whose distribution is limited to small remote islands in the Indian and Pacific oceans. Pisonia trees create immense forests that act as a key foundation of the Palmyra Atoll's terrestrial ecosystem.
A mature Pisonia forest has big trunks spaced far apart and a high, cathedral-like roof of leaves and branches knit together. This canopy cathedral provides valuable nesting habitat for vast numbers of seabirds, such as red-footed boobies, which can perch on and create stable nests in the maze-like branches of the Pisonia trees. In turn, feces from the nesting seabirds deliver important nutrients to the island ecosystem, fertilizing trees and sustaining the local food web.
In contrast, the long, slick fronds of the coconut palm provide no such nesting structure, and seabirds tend to avoid them. Coconut fronds and nuts themselves also crush Pisonia saplings when they fall to the ground.
"As a result, coconut palms are quickly replacing the native forest; bird-nesting sites have shrunk; and ecosystem dynamics are changing,"says Hathaway.
Research findings like this will inform the adaptive-management plans used by the U.S. Fish and Wildlife Service and The Nature Conservancy, who manage the Palmyra system. The research will also help other island territories and nations in the Pacific in sustaining their natural resources.
The USGS and others in the Palmyra Atoll Research Consortium continue to investigate the forests and shores of these islands. Underwater, Palmyra is now one of the world's few unfished coral reef ecosystems, with healthy populations of large predatory fish and sharks. It provides a perfect baseline for comparison with atolls that are suffering from overfishing and poor resource management. This haven, for example, allows USGS WERC biologist Kevin Lafferty and colleagues to explore ideas about the keystones and indicators of reef health—such as how the loss of sharks might cause negative, rippling effects down the food chain, and how a rich diversity of shark parasites might be a sign of a healthy reef.
"That's the key to adaptive management," says Hathaway. "As scientists learn more about the biological functions and processes of Palmyra, resource managers can continue to tweak and improve their strategies for conserving this unique ecosystem."
Note: The original version of this article, with additional links, appeared February 24, 2011, on the USGS WERC Outreach Web page at http://www.werc.usgs.gov/outreach.aspx?RecordID=47.
in this issue:
Palmyra Atoll: Island in Recovery