Humans the biggest threat to sea turtles

The most comprehensive assessment on global sea turtle populations has been released, identifying the most at risk species and regions, and their biggest threats. Not surprisingly, these threats mostly come from humans - in the way they fish, manage the environment, and their contribution to climate change.

The report identified 11 sea turtles to be the most threatened in the world, of which five  were located in the northern Indian Ocean surrounding countries India, Sri Lanka and Bangladesh. The biggest threat was by-catch from fishing, but  the report said this could be eased if monitoring efforts were spread across the region rather than its current policy of being largely limited to the Southwest Indian Ocean.

Australasia was also ranked as a high-risk, high-threat area, even though the length of its coastline meant that it had the most diverse population. The Mediterranean though, was found to be home to the least diverse population because marine populations are concentrated in tropics and begin to decline as latitude increases.

In total five regions were categorized as high-risk high-threat, which were South Asia, Australasia, West Indian, East Pacific and the East Atlantic. Only one region, the Pacific Islands, was deemed to be low-risk low-threat. With the remaining, North Atlantic, Wider Caribbean, and the Southwest Atlantic were categorized as prevalently low-risk high-threat.

The lead author of the study, which was eleased on Thursday in peer-reviewed journal PLoS ONE, was Dr Bryan P. Wallace, the Science Advisor for the Sea Turtle Flagship Program within Conservation International's Global Marine Division. His study was the first to identify and associate multiple factors to assess the global sea turtle population.

Wallace and his team used the low-risk, high risk, and low threat, high threat variants as the basis of the 'conservation priorities portfolio' used to model the seven species of the global sea turtle population. The seven species are able to live in almost every ocean in the world and are internationally listed under four categories; vulnerable, endangered, critically endangered, and data deficient.

The listings were taking into consideration by researchers when they defined the two matrixes of risk and threat. The risk matrix identified internal influences; population size, recent trend, long-term trend, rookery vulnerability and genetic trend. Whilst the threat matrix identified external influences; fisheries bycatch, take (utilization of turtle's – meat, eggs etc), coastal development, pollution and pathogens, and climate change.

However, due to excessive data deficient scores the researchers removed climate change after measuring two thirds of the date. Though it was removed from the study, climate change was evidentially ranked on par with fisheries bycatch as the highest threat to the sea turtle. It was emphasized that presence of critical gaps in monitoring effects of pollution and climate change. Pollution and pathogens were ranked as the lowest threat.

The report concluded that assessing the relative extinction risks is of particular importance to species-focused conservation but that their modelling method was reflective of the reality that conservation priorities vary in objectives and values amongst organisations, including NGOs and researchers. The Indian Ocean was identified and highlight as an area that should be of focus for a reduction of threats, increased monitoring or both, as a means to preserve the sea turtle population.