How Climate Change is Affecting Global Sea Turtle Populations

Climate change effects are seen across ecosystems all around the globe. Wildlife species have been adversely affected by global warming. Rise in sea surface temperature and increasing sea levels are affecting sea turtle populations.

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Climate change has become an increasing threat to species across the planet. It is causing irreversible damage to ecosystems. The effects of a changing climate can be seen on marine biodiversity due to rising sea surface temperatures and rise in sea levels as a result of melting polar ice. These changes can result in biodiversity loss and alter the balance of the natural world.

Rising temperatures lead to ecological changes like the migration of Chinook salmon to Arctic rivers, behavioral changes in species like earlier breeding time for North American tree swallows, and genetic changes like interbreeding due to changes in habitat for example hybridization in common toad and green toad in southern Italy.

Climate change is also causing a significant amount of physiological changes. It’s known to impact reproduction of species in a number of ways, changes in sex ratio, gametogenesis and spawning (speed or timing), fecundity and larval survival to name a few.

These far-reaching effects have extreme consequences for marine life, but some species are impacted more than others.

Sea turtles are one of the most beautiful marine creatures that one can see. There are seven species of sea turtles found across the globe out of which six are endangered.

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But Do You Know That Their Life Is Not as Simple as It Looks?

The life of a sea turtle is a struggle right from the day they hatch till the end of their life, it is a tough fight for survival. Only one out of 1000 sea turtle eggs makes it to adulthood due to natural predators and other obstacles. And now climate change is threatening the very existence of these species. It has been observed that warmer temperatures due to climate change affect the gender of sea turtles during incubation of their eggs, causing an imbalanced ratio of female to male hatchlings across all sea turtle species which could result in sea turtle extinction.

Sea turtle hatchling sex depends on temperature, also known as temperature-dependent sex determination (TSD). When the sea surface temperature rises due to global warming, the sand becomes warm which in turn affects the hatchlings of sea turtles by altering their natural sex ratios resulting in more females than males.

What Does Climate Change Mean for Sea Turtles and How Does Temperature Affect the Sex Ratio of Sea Turtles?

The sex of sea turtle hatchlings is determined post-fertilization. The temperature of the developing egg determines the gender of the offspring. For marine turtles, the pivotal temperature also known as the constant incubation temperature is approximately 29 degrees celsius where there is a 50: 50 ratio of males and females being born. This temperature could however differ slightly among species and across geographical locations.

Scientists have estimated that if a turtle’s egg incubates below 27.7 degrees celsius then the hatchlings will be male but if the eggs incubate above 31 degrees celsius, then the hatchlings will be female.

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Any fluctuations between these temperatures will result in a mixed population of male and female turtles. A higher number of females could lead to skewed incubation conditions and could also push the species to extinction with less number of males to reproduce.

Hotter sand due to climate change could also decrease hatching rates or sometimes result in complete nest failure. This could be a huge disaster in terms of sea turtle populations as they lay eggs in huge numbers.

The number of eggs laid by a sea turtle is called a clutch and it varies depending on the species and size of the sea turtle. On average, sea turtles lay 110 eggs in a nest, with an average of 2 to 8 nests a season. The smallest clutch size is of Flatback turtles with approximately 50 eggs per clutch whereas the largest clutch size is of Hawksbill turtles which may lay more than 200 eggs in a nest. So if most of the hatchlings turn out to be females there will be lesser males in comparison to females to mate with.

Researchers have observed feminization of sea turtle populations around the world. The chances of finding a mix ratio of male and female turtles is rare given the rate at which climate change is accelerating.

A 2018 study shows that 99 percent of the green sea turtle population hatched in Raine Island of Australia were females! The ratio of females to males was 116:1 which is alarming.

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Ray of Hope

Sea turtles play an important role in marine ecosystems. They regulate coastal marine communities by maintaining healthy seagrass beds and coral reefs, balancing marine food webs and facilitating the nutrient cycle. Sea turtles also hold a special cultural and social value to the coastal communities and many countries earn revenue through tourism. Hence, protecting sea turtles from the effects of climate change is extremely important.

There are organizations working toward protecting sea turtle species from the effects of climate change. For example, WWF is working to help protect sea turtle species like Hawksbill, Leatherback and other sea turtle species and their habitats. WWF’s Latin America and Caribbean Programme and the Climate Change Programme are developing a research project to assess the impacts of climate change on Hawksbill turtles, provide a model for assessing future impacts of climate change on other marine species and develop conservation strategies to protect marine turtles from climate change. The first stage of this research project will be for the Caribbean region. Sea Turtle conservancy’s focus is on projects in the Caribbean and Atlantic as these regions are critical nesting sites for sea turtles like Green turtles, Loggerheads and Hawksbill turtles.

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How Can You Help Save Sea Turtles From the Effects of Climate Change?

Planting vegetation, specifically native trees and shrubs, continuous monitoring of turtle nesting sites for temperature (using temperature recorders) and other factors, controlling sand temperature through water irrigation & providing shade and involving local communities in protecting sea turtles nesting sites and turtle conservation projects are some of the methods that can be adopted to save sea turtles from the effects of climate change.

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