Rhett A. Butler, mongabay.com 25 Feb 08;
Logging is having an unexpected impact on endangered sea turtles in Central Africa, reports a new study published in Oryx.
Aerial surveys in Gabon reveal that logs lost during transport are clogging beaches, preventing critically endangered leatherback turtles (Dermochelys coriacea) from nesting.
The researchers — an international team that included William F. Laurance from the Smithsonian Tropical Research Institute and Michael Fay from the Wildlife Conservation Society — found that logs blocked nearly 30.5 percent of Pongara Beach, one of the world's most important turtle nesting areas, during the 2002-2003 and 2003-2004 breeding seasons.
The logs caused multiple problems for sea turtles, including trapping and disorienting turtles, causing them to die; physically blocking access to nesting areas, forcing turtles to abandon nesting altogether or establish nests dangerously close to the waterline (seawater inundation kills sea turtle eggs); and altering the structure of the beach so that turtles were unable to climb steps caused by sand erosion.
Overall 8-14 percent of 2,163 observed nesting attempts were "disturbed or thwarted by lost logs, sometimes with fatal effects for the nesting female".
Given the low survival rate to maturity of marine turtles, the researchers say that displaced logs may be a significant threat to endangered populations. They further note that logs likely impact survival of hatchlings, by impeding their path to the ocean and increasing their vulnerability to predators.
To reduce risk of escaped logs to sea turtle, the researchers recommend establishing a log-removal program supervised by conservation organizations. The salvage program would benefit both turtles and the local communities involved — the 11,000 logs counted in Gabon's beaches during the survey were worth $11.1 million.
Taking a broader look, Laurance and colleagues write that the lost logs "typifies a wider problem of excessive waste and inefficiency in the tropical timber industry... such inefficiency exacerbates pressures on remaining forests, many of which are being rapidly overharvested."
The authors say that better forest management could help reduce waste from timber operations.
Linkages between land and sea
The authors suggest that the impact of deforestation on sea turtles is only one example of the ties between degradation of land and sea ecosystems.
"Our findings bolster the notion that important linkages exist between terrestrial and marine ecosystems," they write. "Coral reefs, for example, can be seriously degraded by sedimentation from nearby deforestation... and by algal blooms caused by phosphate and nitrogen pollution."
"In coastal West Africa depletion of marine fisheries has led to increased hunting pressure on terrestrial wildlife," they continue. "The rapid destruction of mangrove forests, which provide nurseries for many fish and shrimp species, is having serious impacts on coastal fisheries... Plastic waste is pervasive in the world's oceans and is a particular threat to leatherback turtles, which can choke to death on plastic debris they mistake for jellyfish, their principle food."
Marine turtles, like many other species, face a multitude of threats, both on land and at sea.
