Marine turtles face a number of challenges to survive as a species in the 21st century from habitat loss to pollution.
Turtles require a number of key habitats in order to thrive: from beaches to lay their eggs to seagrass pastures, coral reefs and open ocean areas to feed. As human populations expand and industries expand alongside them, many beaches are being rapidly taken away from turtles and overrun by hotels, industrial complexes and beachside villas. When we think of habitat loss we must be aware that loss of beaches is just one aspect of the problem, and that the loss of underwater feeding habitats are equally as destructive.
Increasingly the fishing industry is having a massive impact on turtle mortality. As fishers cast their nets and leave them at sea overnight, turtles get caught accidentally and drown. Sometimes turtles swim into fish traps set on the seafloor looking for food and sometimes get tangled in the float lines used to recover these traps.
Turtles also get caught in fish and shrimp trawl nets and drown as they cannot come to the surface to breathe. At high seas, turtles accidentally get entangled in long-line gears or go after the bait only to end up being hooked just like the target fish.
Human harvests and collection of eggs
One of the biggest problems is the collection of eggs from beaches. When turtles emerge they are particularly vulnerable to poaching and their eggs are completely defenceless. People collect the eggs as food and also as aphrodisiacs (although there is absolutely no ‘secret’ chemical in turtle eggs and they are pretty much the same in content as a chicken egg). Adults are also collected for food as they emerge to lay eggs and when they are swimming freely in the oceans.
Pollution comes in many forms: chemicals which damage coral reefs and seagrass habitats; plastics which turtles regularly mistake for jellyfish while juvenile turtles injest plastics as they feed on floating materials which they can also get entangled in.
Pollution also comes in the form of light: turtle hatchlings are guided to the ocean by the brighter horizon out to sea compared to the darker horizon inland. But since humans have started to live closer to the shorelines, bright lights behind the beach from hotels and homes result in hatchlings being attracted inland where they are frequently lost to predators and dehydration. Adult turtles also avoid nesting on bright beaches - which in many countries is all of the beach!
Nets discarded at sea or lost in storms continue fishing long after they leave the boat. Hundreds of turtles drown each year in the nets which are no longer of any use to people.
As sea levels rise, beaches become narrower and shallower. A narrower beach offers less nesting area while a shallower beach means turtles may not be able to lay their eggs as deep as they would like and may abandon the site altogether both resulting in drastic consequences.
Leaving the site means no more eggs will be laid there while hatchlings born on these beaches will be imprinted with details of the area they need to return to as mature adults to lay their own eggs. In the long run this will mean the disappearance of all turtles from the beach in question. Because the gender of the hatchlings is determined by the temperature of the nest during egg incubation, shallow nests are a real worry to the future turtle population because if nests are shallower, they will be warmer and therefore produce more females. The extreme case could be a nest that produces only females and no males, signifying the beginning of the end of the population.
While not a direct threat, the cumulative effect of multiple impacts can severely deplete a turtle population. While the populations might be able to deal with nesting beach loss, for instance, and move to a new location, this might be a catastrophe if that second location is wiped out by recurring and more-frequent storms as a result of climate change.
If turtles are to survive on this planet, it is up to human beings to minimise the cumulative effects of all these threats, by eliminating those that we can as rapidly as we can.