Leatherback turtles, which were listed as a critically endangered species in the International Union for Conservation of Nature’s Red List of Threatened Species in 2000, are now listed as vulnerable — two notches higher in terms of their survival. However, a number of factors still pose a threat to them and their breeding, and logging in tropical forests is among them, a study found.

Leatherback turtles (Dermochelys coriacea) live mostly in the water, and travel long distances worldwide in their migrations, making them vulnerable to being caught in fishing nets as bycatch. They come onto beaches during the nesting season, but many of those sites are now disturbed due to the presence of tourists. And the study, published Friday in the journal Marine Ecology Progress Series, highlights the previously underestimated risk from logging.

Titled “Impact of tropical forest logging on the reproductive success of leatherback turtles,” the study was carried out by researchers from Doñana Biological Station in Seville, Spain, and the University of Exeter, United Kingdom. The researchers monitored 216 turtles in one of the world’s most important nesting sites in Colombia, under conditions where the beach was strewn with varying amount of logging debris.

Leatherback turtle hatchlings struggle with a log on the beach. Juan Patiño

Organic debris from logging in tropical forests turns up on many beaches, being carried to the coast by rivers and concentrated by oceanographic processes, and once there, it has a negative impact on the reproduction of D. coriacea. The female turtles need to come out of the ocean and cross sandy beaches to dig their nests, where the eggs incubate. The hatchlings, once they emerge from the eggs, have no parental care and must cross the beach on their own to get to the safety of the water.

The study found that female turtles which nested in areas with high amounts of debris spent more time building their nests, and that the nests were closer to the water, compared to the females who nested in areas with lesser debris. This made the nests more vulnerable to flooding by waves, and some females were also injured in the process of building nests.

On the other hand, once hatched, the young turtles would take longer to reach the sea, making their way across the obstacles posed by the debris. This would expend more energy and they would be more exposed to potential predators.

Adolfo Marco Llorente of the Doñana Biological Station said in a statement Monday: “Although logging debris does not affect rates of nesting, it has a significant impact on where and how nests are built, which negatively affects both mothers and hatchlings. This is on a scale that could lead over time to reduction of the overall population. Simple measures could make a real difference, such as repositioning organic waste areas, or salvaging the wood debris as an energy source. It’s also essential that logging practices that reduce the impact on the marine environment are implemented.”