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 from threats.
USGS Western Ecological Research Center biologists are part of a research consortium studying the forests and waters of this U.S. territory. In the 1940's, Palmyra Atoll served as a U.S. military outpost, and now Palmyra faces challenges from past habitat impacts and ongoing concerns with invasive species and sea level rise.
A Not-So-Lovely Bunch of Coconuts
A USGS report released in January authored by WERC's Stacie Hathaway, Kathryn McEachern and Robert Fisher recommended habitat management strategies for Palmyra. One finding casts the coconut palm in a villainous role.
Coconut palms, a species that was being farmed in local plantations, are taking over the island landscape (see top photo). The palms are driving out a rare, native tree species called Pisonia grandis -- which create immense forests that act as a key foundation of the Palmyra Atoll's terrestrial ecosystem.
As McEachern recently described to Greenwire:
"In the most mature state, you'd be walking through a forest that has big trunks widely spaced apart, but it would be like looking up in a cathedral with a green roof, all the leaves knit together."
This canopy cathedral also 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 Pisonia trees. In turn, feces from the nesting seabirds delivers important nutrients to the island ecosystem, fertilizing trees and sustaining the local food web.
|Many organisms depend on Palmyra's terrestrial ecosystem, including red-footed boobies (top), this undescribed gecko species (middle), and the robber crab (bottom). Image credit: Stacie Hathaway/USGS.
In contrast, the long, slick coconut palm fronds 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.
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 comparison against atolls that are suffering from overfishing and poor resource management. This haven allows WERC biologist Kevin Lafferty and colleagues to test ideas about the keystones and indicators of reef health -- like how 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."
-- Ben Young Landis
Top: Coconuts may conjure the image of paradise, but on the Palmyra Atoll, coconut palms (lower image) are pushing out rare Pisonia trees (upper image) and disrupting the nutrient and bird nesting cycle of the island. Image credit: Stacie Hathaway/USGS.