Habitation harms turtle fertility

ScienceAlert 9 Sep 08;

'How's the serenity?' We all love peace and quiet when it comes to a get-away, but for marine turtles it appears that nesting on beaches untouched by human development actually affects the number of offspring born.

David Pike, a PhD student in the School of Biological Sciences at the University of Sydney, has found that two species of marine turtle - the loggerhead (Caretta caretta) and green turtle (Chelonia mydas) - produce more babies when nesting on natural beaches compared to those with human development.

David's work is the result of an extensive scientific literature survey of journal articles published from 1900 to 2007 from around the world.

"Coastal ecosystems provide vital links between aquatic and terrestrial habitats, so they support extremely high levels of biodiversity," David said. "But, of course, we humans also love coastlines - they have the highest densities of human development anywhere on the planet.

"Beaches are a favoured destination for tourists, but are also a critical habitat for nesting sea turtles, so we have a situation where the potential for negative effects on these species is extremely high."

The data gathered on marine turtle reproductive output showed that female loggerhead and green turtles nesting on natural beaches produced more hatchling turtles per nest when compared to those nesting on beaches with permanent human development.

"Females who successfully produce more offspring will have higher lifetime reproductive success than females of the same species who produce fewer offspring.

"My study indicates that female marine turtles nesting on natural beaches are likely to have higher evolutionary fitness than female turtles nesting on developed beaches.

"This difference in the number of eggs that hatch has important implications for increasing the numbers of marine turtles that are out there.

"Over the last century numbers have plummeted because many fisheries practices accidentally capture and drown adult turtles. Protecting the remaining natural beaches may help build numbers in the coming decades."

The research highlights the conflict between coastal development and sea turtle conservation, and shows that protecting and maintaining natural beaches will benefit sea turtle populations.

Marine turtles are ecologically important in both marine and terrestrial ecosystems and are distributed in tropical, temperate and even sub-arctic waters worldwide, although they nest only in tropical and temperate regions.

David's research has been published in the UK Royal Society journal Biology Letters.