Good News for Green Turtles: 50 years of conservation gives huge boost to nesting population.

Reference: A.M Pritchard, C.L Sanchez, N Bunbury, A.J Burt, J.C Currie, N Doak, F Fleischer-Dogley, K Metcalfe, J.A Mortimer, H Richards, J van de Crommenacker, B.J Godley. (2022) Green turtle population recovery at Aldabra Atoll continues after 50 yr of protection. Endangered Species Research. 47: 205. DOI: 10.3354/esr01174

Good News for Green Turtles

Green turtles have suffered a long history of exploitation at the hands of humans who, since at least the 18th Century, have harvested them for their meat and shells. As these hunting practices became industrialised, turtle populations plummeted. However, not all hope is lost. A new study, based on fifty years of turtle nesting data, shows that over time, we may be able to make amends and help to protect the natural world which we so often take for granted.

The researchers found that since conservation measures were introduced in 1968 on the island of Aldabra in the Seychelles, the number of green turtle egg clutches laid there has risen by up to 665%. This equates to an increase of almost 3% each year. As a result, there could be as many as 5099 female green turtles nesting on the island.

Tracking Turtle Tracks

To assess the green turtle population on Aldabra, lead author Adam Pritchard and staff from the Seychelles Islands Foundation analysed fifty years-worth of data collected from over forty thousand track count surveys. These surveys had recorded and categorised turtle tracks found on fifty-two of the island’s beaches. Based on these data, the researchers were able to estimate the number of turtles using each beach and therefore the island’s population as a whole.

Green turtle tracks on a beach on Aldabra. Image source: David Stanley

The researchers also estimated how many clutches of eggs were laid on the island each year. This figure has risen from an average of 5606 between 1980 and 1985 to an average of 15,296 between 2014 and 2019. Previous studies, which explored the nesting behaviours and trends of green turtles on Aldabra, helped the researchers analyse data from the track count surveys and produce this estimate. Understanding how many clutches are laid each year provides insight into the health of the population and how quickly it is growing.

One of the first conservation strategies to be implemented on Aldabra in 1968 was a complete ban of turtle harvesting. Later on, designated protected areas were created which allowed the green turtles to nest in peace.

The current number of turtles is still much lower than the estimated 6000-8000 female turtles that had nested on the island before intense harvesting practices began. However, the results of this study show that the conservation strategies on Aldabra are working as planned. The researchers hope that the green turtle population on the island will continue to increase.

A Conservation Case-Study

The programme of green turtle protection and monitoring on Aldabra has been in action for longer than any other similar projects in the Western Indian Ocean. Thanks to these efforts, the population of green turtles on Aldabra is now the second-largest in the region, behind only that of Europa in Iles Eparses. As such, these conservation efforts can provide a blueprint for other similar programmes in the region and around the world. Indeed, the study’s lead author, Adam Pritchard, said that “It’s been an honour to record the continuous population increase of Aldabra’s green turtles and help deliver a much-needed ‘good news’ conservation message which will hopefully encourage similar programmes”.

A green turtle digging a nest. Image source: Deanna Keahey

But, the work at Aldabra is far from done. The researchers also found that more turtle tracks have been blocked by debris or beach erosion in recent years. This may be linked to the vast amount of plastic debris building up on the island’s beaches and the rise of sea-levels due to climate change which are expected to reduce the island’s land area by 25% before the end of the century.

The incredible conservation work being carried out on Aldabra is not a happy ending under which we can draw a line in the ever-eroding sand. Instead, the work of the Seychelles Island Foundation and researchers like Pritchard should be seen as a foreword to an ever-increasing number of successful conservation programmes around the world.

Cover photo by Reiner Kraft

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