Marine plastic pollution is causing alarming declines in Sea Turtles

Marine plastic debris is estimated to have killed 52% (340,000) of sea turtles globally through entanglement and ingestion. Scientists have revealed regions which pose the highest risk to sea turtle populations, through elevated levels of plastic debris. Subsequent advice has been given to place high priority on the reduction of further debris inputs to these areas.

Annually an estimated 4 – 12 million tonnes of waste plastic is released into our oceans, a fact that is rapidly becoming one of the critical environmental concerns facing wildlife in the 21st century.

Over the last century, our increased usage and reliance on plastics has revolutionised the way we live. However it is our high demand for plastic and neglectful release of man-made debris into the natural environment that is damaging other species, particularly marine wildlife. Of the 693 species recorded to have been affected by marine plastic debris, sadly two of the top six most heavily affected are sea turtles!

Research undertaken by the University of Queensland, found that Olive Ridley turtles are most susceptible to mortality from plastic due to their diet and foraging strategies. Adults eat a wide variety of foods ranging between locations, though a common dietary component is jellyfish. It is understandable, given the physical characteristics of plastic and the simple visual capacity of the animal, how plastic could therefore be mistaken for food.

Plastic debris ingestion is not only a problem on its own, but is an additional threat to turtles that already face a multitude of stressors.

Sea turtles face threats from multiple sources including coastal development, global warming and entanglement in fishing gear. Plastic pollution is an additional stressor which ultimately could be avoided if greater care is taken.

Researchers have undertaken a risk assessment, combining global marine plastic distributions with sea turtle habitat maps to predict the turtle exposure levels to plastic pollution. This revealed the regions of highest risk to global sea turtle populations; located off the east coasts of the USA, Australia and South Africa, Southeast Asia and East Indian Ocean.

The global risk maps show age to be a critical factor determining ingestion. Indeed oceanic sea turtles; usually early juveniles, that pass through large oceanic currents experience an increased likelihood of ingestion. However there are some populations of loggerhead and green sea turtle that utilise oceanic habitats even as adults, which is more concerning. Increased mortality of adults could have an even greater population impact, as sexual maturity can take between 12 and 50 years in these species.

It is hoped that this research can be used to prioritise efforts in reducing plastic debris accumulation and subsequent ingestion by sea turtles, via minimising debris inputs to these areas along with the removal of existing debris.

WWF, SEE Turtles and other conservation charities are trying to minimise the effects of plastics on sea turtles by reducing other risks. These include eliminating bycatch, protecting marine turtle habitat, addressing illegal trade of sea turtles, and through improving hatching success rates. SEE Turtles supports sea turtle conservation through ecotourism, fundraising and education.