Will Sea Turtles Survive the Anthropocene?
The modern day sea turtle has existed for around 80 million years, and they can be found in all ocean waters except the polar regions. There are now only 7 living species left in the world, so it is important to protect those that remain.
Of the 7 living species, 2 species are critically endangered, 1 species is endangered, 3 species are vulnerable and 1 species is data deficient. Threats to these incredible creatures fall more recently at our own feet. In the past they have been over-fished through by-catch, but in recent years climate change, coastal development, and more importantly marine debris are the biggest causes of sea turtle decline worldwide.
Climate change –
The rise in sea levels has in some cases reduced coastal areas and historic nesting grounds of many sea turtles. This, combined with coastal development and beach erosion, is limiting the amount of beach space available for the turtles to dig their nests, causing them to move further afield and in some cases nest in areas that are not ideal, resulting in the loss of nests and the next generation of sea turtles.
Rising air temperatures are causing sand temperatures to increase, which interferes with the sex-determination of incubating sea turtle eggs. Like other reptiles, the sex of developing embryos in sea turtles in not determined by genetics or chance, but by temperature, with warmer temperatures leading to females and cooler temperatures yielding males. Normally, in a clutch of eggs, the eggs in the center of the nest are of a slightly elevated temperature, leading these eggs to become female. Those that sit on the outside of the nest are of a cooler temperature and will eventually become males. The pivotal or optimum temperatures for these nests are between 28-31 degrees Celsius, however anywhere between 25-35 will also hatch.
As sand temperature increases with climate change, the temperature of the eggs within the nest also increase. If the eggs become too hot, they will no longer hatch or the nest will become predominantly female eggs.
In contrast to this, as climate change causes more dramatic changes in seasonality and rainfall, the increase in rainwater and runoff can cause the nests to fall in temperature. This drop in temperature will cause the eggs to cool down, in some cases the low temperature will halt the eggs development or will lead to a nest of predominantly male eggs.
This effect may not seem important now, but as weather becomes more unpredictable and we worry about if we need to bring a coat or an umbrella when we leave the house, a turtle is worrying about if it will find a mate, or if due to the changes in the climate there will be fewer males or females making it to maturity.
Coastal development –
As human populations increase worldwide, the demand for resources as well as space for development is causing more pressure on coastal areas worldwide. Coastal areas are being lessened to make way for new complexes, holiday resorts and more. In fact, coastal areas are the fastest growing areas around the planet, as coastal megacities continue to attract workers from rural areas. Areas that have been historic nesting grounds are now in decline or at risk of being lost completely. These developing areas also mean that there is an increase in proximity between sea turtles and humans. Whilst in some cases this proximity is a good thing as it helps raise awareness about the plight of the sea turtle, it can also swing the other way.
In September 2015, hoards of tourists landed on a historic Olive ridley nesting beach in Costa Rica. These tourists through sheer stupidity then proceeded to crowd, pick up and sit on turtles to take photos. In some cases the turtles became so stressed that they returned to the sea without laying the eggs. This behaviour from our kind could potentially reduce the number of Olive Ridleys that would use the beach in the future further reducing another nesting ground.
As more and more turtles are nesting on beaches that are part of, or outside of resorts it is important to remember that although we can all agree that holiday makers would love to wake up and see these incredible creatures nesting, it becomes more difficult to protect the nest and the hatchlings from humans as well as the rubbish they leave behind.
Marine Debris –
Some of the biggest and most alarming threats to sea turtles in recent years comes from our own hand in the form of marine debris and trash. Single use plastics, such as bottles, bottle caps, plastic bags and straws are some major contenders, along with cigarette butts and petroleum or oil based products. It is estimated that 13 million tonnes of plastic debris is dumped into oceans worldwide every year. A further estimation is that around 52% of all sea turtles will have ingested some form of plastic throughout their lives.This is likely due to their feeding habits especially as juveniles. At this early stage of their life sea turtles are omnivorous, so they will eat anything and everything they are able to get hold of so that they can increase their size to reduce the risk of predation, it is only later in life that they will switch to their preferred food sources.
Plastics are a major concern as in some cases turtles are unable to tell the difference between plastics and food. Species that feed on jellyfish can easily become confused by a plastic bag and will often ingest them. Juveniles that spent their formative years floating on the surface in pelagic seas often consume anything that floats into the microhabitat in which they live. This can include microbeads, cigarette butts, plastics and more. Another concern for these juveniles is that they are also likely to ingest trash that has become covered in pollutants, chemicals, and toxins which can be deadly.
However it is not just plastics, there has in recent years been a significant increase in the number of toxins that are making their way into marine food webs, both in the plastics themselves and in liquid form. The pollutants that contaminate the food that these turtles consume can be in the form of toxins, fertilisers, petroleum, oil, and other novel chemicals which usually find their way into coastal waters by urban runoff. These pollutants have recently been linked with a disease that greatly affects sea turtles known as fibropapillomatosis. The disease believed to be a strain of the herpes virus often kills turtles if not treated as if forms tumours on the face and flippers preventing the turtle from eating, diving and avoiding predators.
Discarded ropes and nets create a further problem for these air breathers. If turtles become tangled in nets or caught on lines then they will be unable to take a breathe at the surface and will sadly perish. These discarded items also create a further problem as turtles are often caught entangled in them. This entrapment can cause loss of circulation and ultimately the limb, or can prevent the turtle from being able to dive or swim.
What can be done? –
The biggest thing that we can do is to think about where our trash ends up. Limit the use of plastics, if you don’t need a straw or bag then say no. Take part in beach and underwater clean ups to help remove the trash that has already made its way into the ocean.
Raise awareness about the plight of these incredible creatures, if you see someone littering kindly ask them to pick it up. Use organic or biodegradable products that will not harm marine life if it ends in waterways that run into the oceans.
We cannot possibly hope to combat this problem without working together, nor do we want to be the generation that is responsible for the eventual extinction of such incredible creatures because we couldn’t spare a few minutes to pick up some trash or change our habit of not thinking about where the rubbish or products we use ends up.
To help raise awareness we have also created a turtle care card to explain how best to deal with a sick/injured turtle if they are found. This includes the correct way to hold them and the recovery position. It was designed for use around the island of Koh Tao after experiencing injured, sick and more often than we would like dead turtles. It is aimed at ensuring that if a sick turtle is found it can receive the necessary treatment until it can be taken to a professional that can correctly treat the needs of the turtle.