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Evidence suggests sea turtles have been on earth for between 200-300 million years, making them true “dinosaurs” of the sea. Despite being able to survive for so long on an ever changing earth, the sea turtles latest challenge, humans, could be mission impossible. According to the IUCN red list of endangered species, six of the seven existing species of marine turtle are at risk of extinction. Marine turtles are born with the odds already stacked against them with only about one in 1,000 turtle hatchlings surviving to adulthood. Now humans are applying even greater pressure onto these species giving them a bleak outlook.
Marine turtle populations are having to fight a war of survival on many fronts. Firstly turtles must try to avoid the vast amount of fishing vessels that occupy their oceans. Unsustainable fishing practices are leading to turtles getting caught in drift, gill and shrimp trawl nets and getting snagged on longline hooks. Around 40% of all animals caught in fisheries are unwanted and discarded as trash. This is called bycatch, unfortunately this figure accounts for a large amount of turtles being caught in these giant nets and thrown back into the water either dead or half alive. Unable to surface to breathe, many turtles drown after becoming entangled in fishing lines or ensnared by nets. Other turtles, lured by fishing bait, become hooked and sustain injuries that can still kill them even if they are released.
Furthermore, recent research has discovered that some fisheries are actually targeting turtles, whether legally or illegally. People hunt marine turtles for their meat and eggs, which in some places are considered a delicacy. Turtle products such as shells and leather can fetch a high price on the black market making them highly sought after. A new study has found that 42 countries or territories around the world permit the harvest of marine turtles, estimating that more than 42,000 turtles are caught a year by these fisheries and a vast amount more by illegal trades.
Moving on, a further problem which turtles face is one that we can all take some blame for. Turtles habitats are been taken over by our litter. Studies show 36% of Australian sea turtles are affected by marine litter, with 18,000 pieces of plastic litter floating on every square kilometre of the world’s oceans. Balloons, plastic bags and straws, nylon rope and even flip flops are providing a deadly diet for sea turtle populations as they mistake the litter for their prey. Once ingested, the plastic causes a gut impaction which leads to the contents of the animals gut decomposing. The turtles become positively buoyant and can no longer dive down to eat, they can’t get out of the way of predators or get out of the way of oncoming boats, leaving turtles to die a slow painful death. Studies show that at least half of the world’s sea turtles have ingested plastic or other human rubbish.
Marine turtles are been effected at all parts of their life cycle. Unsustainable tourism and poorly planned coastal developments are destroying turtle nesting beaches and polluting their feeding grounds. Highly populated sea fronts create large disturbances for nesting sea turtles and direct damage to the nests themselves. It is also thought that light pollution along the coast at night is disrupting visual cues of turtle hatchlings. Visual cues are important for marine turtles for things such as finding the sea after nesting or hatching. Hatchlings are being attracted to lights and crawl inland or aimlessly down the beach getting lost and leaving them more vulnerable to terrestrial predators.
Following on, perhaps the most alarming issue is that of climate change. The global issues of climate change looks as if it will affect our marine turtle populations in a devastating way. With rising sea levels the available nesting sites will be vastly reduced for all turtle species. Nesting areas that are left intact could still however prove to be unsuitable due to high temperature rises. Sea turtle eggs only develop successfully in a relatively narrow thermal range of approximately 25-35c, so if incubation temperatures are too low the embryo does not develop but if they are too high then development will fail.
However, even if the temperatures don’t reach this thermal maxima, the temperature increases could still have a drastic effect on populations by upsetting the sex ratios. The sex of turtle hatchlings is determined by the temperature at which the eggs develop in the nest. Nest temperatures above 29c produce a clutch of mainly females while below 29c more males are born. Climate change is already changing the sex ratios in many marine turtle populations, leading to too many females. While it is known that males can mate with more than one female during the breeding season, if there are too few males in the population this could threaten population viability.
The outlook for marine turtles does look bleak, however things are been done to try and rescue all marine turtle species from the brink of extinction. Things such as turtle excluder devices have reduced sea turtle mortality in trawl fisheries and some counties in Florida make residents turn off beachfront lights during nesting season. None the less these ideas are not regulated worldwide and don’t deal with larger, more global problems. Governments and large corporations (fishing) need to take responsibility by putting into place stronger and more regulated rules on the fishing industry, coastal management and tourism management.
It seems as if climate change could be the biggest issue for marine turtles due to the fact we cannot directly or immediately halt the issue. In order to help sea turtle populations cope with such a powerful issue, we must do what we can to protect them from the existing known harms that we can have a direct effect on. We as individuals could also help by buying ocean products that are sustainable and by reducing our plastic intake and waste. We may see turtles on our nature documentaries and Disney movies all the time, but if we don’t act fast then this could be the only way we see them. Populations are crashing and programmes need to be put into place now, in order for us to keep a species that we are currently pushing to extinction.
