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NEW research has shown that sea turtles have adapted in the past - the question now posed, is can they do it again?
New research from Australia shows that flatback sea turtles have
made radical changes in their behaviour to adapt to changing climates over the last 10,000 years. This suggests they may be able to adapt to future climate changes, but possibly not quickly enough to survive the dramatic changes predicted by some climatologists.
Marine turtle scientists and researchers from around the world met recently at the International Sea Turtle Symposium in Myrtle Beach, S.C., to share their latest data and discuss the implications for survival of the species. Not surprisingly, climate change and
its impact on turtle populations was a primary topic of scientists’ presentations.
Australian research gave hope for future turtle populations, while studies conducted in North Carolina showed alarming news for North American loggerhead turtles. A new study on leatherback turtles revealed that climate change is a significant factor in the
rapid decline of the species in the Pacific Ocean.
The new research conducted in Queensland, Australia, explores how a present day population of flatback sea turtles might respond to climate change, looking back at how they’ve changed behaviour in the past to adapt to the environment. Prior to the last ice age, sea levels were significantly lower, so the coastline and turtle nesting beaches were further out, as far as 1,200 kilometres (745 miles) from their present day locations. By the time the last ice age ended, 4,000 years ago, sea levels had risen significantly. The flatback turtle adapted by finding new nesting sites and foraging areas.
Dr. Colin Limpus of Queensland Turtle Research believes that today’s turtles can respond to new climate change impacts, given the opportunity.
“The flatback will likely continue to lay on some existing nesting beaches with elevated dunes, simply by crawling higher
up the beach to lay,” said Limpus. “We will likely see this at suitable beaches such as Wild Duck Island.”
This is a major flatback nesting site within the Great Barrier Reef, off the northeastern coast of Australia.
Limpus cautions that not all existing nesting sites will be sustainable under rising sea levels. “Some sites are at high risk of erosion and eventual loss,” explained Limpus. “Low sand islands will almost certainly flood over,” he adds. In addition, developed coastlines with hotels, houses, sea walls and other man-made structures leave no place for the turtles to go as the sea rises.
Perhaps a bigger concern among scientists is the direct effect of global warming on nesting beaches – higher sand temperatures. When the nest becomes too hot, the hatching success rate drops, sometimes dramatically. In Australia, Limpus has seen decreases in incubation rates of 25% since 1998. “Since 1998, beach temperatures have
been over 32 degrees Celsius (90 degrees Fahrenheit) for most of the breeding season,” he said. “That’s too warm for turtles to hatch.”
One of the most important effects of temperature on marine turtles is in determining gender. The sex of turtle hatchlings is determined by the temperature of eggs during incubation. Warmer nest temperatures produce females and cooler nests result in males. Research by UK and US scientists analysed 26 years of North American loggerhead turtle nesting and climate data and compared the findings with models for future temperatures. In North Carolina 42% of hatchlings are presently male, compared to just 10% further south in warmer Florida.
According to Lucy Hawkes of the Marine Turtle Research Group at the University of Exeter (U.K.), these ratios could soon change. “With just two degrees Celsius of warming, there would be no more males produced at Cape Canaveral, Florida,” states Hawkes. It’s widely accepted that three degrees Celsius will occur in the next 100 years,
which could be disastrous for Florida loggerhead populations.
According to Hawkes, three degrees of warming would cause nests to incubate above the lethal threshold, reducing hatching rates.
The threat of temperature increases is exacerbated by human activities. Dr. Matthew Godfrey, sea turtle coordinator for the State of North Carolina, believes that beach “nourishment” activities, common in the Carolinas and Florida, can cause more problems
for the turtles. “The renourishing material is drawn from the seabed floor, and is often darker,” explained Godfrey. “The darker sand produces warmer incubation temperatures.”
However, research may not be enough to protect the species from the worst-case climate change scenarios. “The world has to come to terms with climate change and adapt our behavior to protect threatened species such as sea turtles,” said Limpus. “If we’re successful with sea turtle populations, that will be a good indicator of success in maintaining biodiversity throughout our oceans.”
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