Buying time by lowering beach temperatures for the loggerhead turtle
Climate change is one of the greatest threats facing the endangered loggerhead turtle. While rising sea levels are impacting where this majestic sea traveller can lay its eggs, a more critical factor is the temperature of the beach sand. While governments and communities worldwide strive for solutions to climate change, at Mon Repos in Queensland, a dedicated team is buying more time for the loggerhead turtle.
Mon Repos is the most significant loggerhead turtle nesting population in the South Pacific Ocean region and is a culturally significant place for four identified First Nations groups—Taribelang Bunda, Gooreng Gooreng, Gurang, and Byellee peoples. It is known as a meeting place to perform sacred rights, gather turtle eggs and shellfish to eat, and make stone tools.
Queensland Parks and Wildlife Service (QPWS) Chief Scientific Officer Dr Col Limpus knows the area well. He grew up near Mon Repos before becoming a leading expert in sea turtle conservation.
Col has led research at Mon Repos for decades.
“Since the 1960s, temperature records show that the beach is getting hotter,” Col explained.
“For sea turtles, temperature determines the gender of the loggerhead turtle embryos about halfway through incubation. Males result from cooler temperatures and females from warmer ones. What we have seen as the temperature rises is the increasing feminisation of turtle eggs.
“As the eggs develop, they also create heat, increasing the temperature of their nest further. If the beach temperature is warmer and the nest temperatures move beyond 31 degrees at hatching time, we see increased mortality.”
Following 2005, a heatwave year, the Mon Repos team started investigating ways to cool the beach sand.
“We experimented with shaded hatcheries to cool the sand,” Col said. “The monitoring was labour-intensive, and we had to gather and relocate the eggs to the shade.”
“In 2018, we started trialling artificial rain to cool the beach temperature spike. We set up an irrigation line and beach sprinklers and tested when to use artificial rain during the day and how much we needed to cool the sand effectively. Eventually, we established that an hour in the heat of the day worked best.”
At this point, the Great Barrier Reef Marine Park Authority, concerned about the increasing feminisation of green turtles on Raine Island and having witnessed the work at Mon Repos, decided to fund a long-term study exploring options for cooling the sand to increase certainty for male hatchling production and incubation success. The Mon Repos team has completed the second year of research and is analysing the data.
Concurrently, in 2022, after 20 years of negotiations, the Queensland Government acquired the farmland behind Mon Repos. The intent is to reestablish the swamp land that used to occur behind the adjacent dune nesting habitat and increase the flow of freshwater above the underlying basalt soils, increasing the evaporative cooling of the nesting habitat.
As a result of this proactive conservation management-focused research, Queensland Parks and Wildlife Service is providing leadership in countering global warming impacts on localised marine turtle nesting beaches while, on a global scale, governments strive to address global warming.