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Thirty years of marine turtle research in the northern Great Barrier Reef

This year marks three decades of marine turtle monitoring in the far northern Great Barrier Reef by the Department of Environment and Science.  Scientists from Queensland Parks and Wildlife have been monitoring nesting turtles, on a remote coral cay called Milman Island since 1990.  This very remote area located almost at the tip of Cape York Peninsula within the Great Barrier Reef Marine Park, supports some of the world’s largest nesting populations of the “Endangered” hawksbill and “Vulnerable” green turtle.

Things have changed a lot over the last 30 years.  In the early days safety schedules were called-in on a HF radio, to Charleville, if we could skip a signal off the ionosphere, once or twice a week and if we were lucky, we could get a weather report on an AM radio.  There were no such things as laptops!  Now we use satellite phones, “SPOT” trackers and collect data using an App on your phone that has an inbuilt Global Positioning System.

But the month-long camps, late nights walking around a beach in torrential rain and trying to sleep during the day in 43C0 in the middle of the wet season, have all been worth it because over the last three decades we have collected one of the most comprehensive, long-term datasets for these globally significant hawksbill and green turtle nesting populations.

Why is this important? Don’t turtles just do whatever they have done for the last 100 million years? Well yes and no.  Marine turtle populations have been impacted by many human caused things over the last 200 years- industrialised fishing, unsustainable take, marine pollution and feral animal predation of their eggs.  Now we are looking down the barrel of climate change induced threats including- sea level rise with a loss or degradation of nesting and foraging habitat, and 100% feminisation due to increased incubation temperatures. 

In an article recently published in Biological Conservation we have shown that the hawksbill nesting population has declined by about 57%.

“Not only did we look at the number of turtles coming ashore each night to nest, we also looked at the number of eggs laid and size of the turtles nesting” said Dr Bell the lead author on the study.  All three indicated a severely declining population.

It’s hard to know what the specific cause of this decline was.  However the biggest threat is probably the take of hawksbill turtles to feed an insatiable desire for hawksbill jewellery made from their shells called “tortoiseshell” as well as being hunted for food on their foraging grounds in the western Pacific.  In fact, between 1844 and 1992, more than nine million turtles were killed, mainly for the tortoiseshell trade, according to a recent study.

A recent island geomorphology study conducted by Professor Scott Smithers and Dr John Dawson at James Cook University, has predicted an approximate 1.5m sea level rise by 2080 in the northern Great Barrier Reef.  We know this will impact nesting turtles…but how?  We are now working to define specific nesting habitat[s] and trying to determine if and what changes may be happening. 

Only by knowing what was there and what is now happening in important turtle nesting and foraging habitats will we be nimble enough to be able to develop sound conservation management strategies to be able to protect them.  I wonder what the next 30 years will look like…maybe we can do it using drones?