Effects of Climate change on Sea turtles

Sea turtles are found in all oceans except for the Polar Regions. They mostly can be found in coral reefs and some species are known to travel between oceans. Sea turtles are generally found in the waters over continental shelves. During the first three to five years of life, sea turtles spend most time in the pelagic zones floating in seaweed mats. Green sea turtles, which are common species nesting in Lamu, in particular are often found in Sargassum mats, where they find shelter and food. Once the sea turtle has reached adulthood it moves closer to the shore. Females will come ashore to nest on sandy beaches during specific seasons usually between Aprils to Septembers in Lamu, North coast of Kenya.

Green turtle hatchling - Photo: Hassan Bwanamkuu

Sea turtles worldwide face a variety of threats that have threatened their existence. The top five threats that endanger sea turtles are:

• Fisheries By-catch – Worldwide, hundreds of thousands of sea turtles are accidentally caught in shrimp trawl nets; long-line hooks and gillnets every year.
• Pollution – Plastic pollution, oil spills, and chemical runoff have all impacted sea turtles.
• Coastal Development – sea turtles are dependent on beaches for nesting. Uncontrolled coastal development, vehicle traffic on beaches and other human activities directly destroy or disturb sea turtle nesting beaches around the world. Feeding grounds such as coral reefs and sea grass beds are damaged and destroyed by activities onshore, including sedimentation from clearing of land and nutrient run-off from agricultural activities uphill.
• Direct Take/Poaching – Sea turtles and their eggs are taken by people (both legally and illegally) in many parts of the world for consumption and use of shell material for handicrafts and jewelry. 
• Lastly, Climate change – Sea turtles' lives are dictated, in large part, by heat: subtle temperature variations shape their embryonic development, determine their sex, and influence their growth and nesting activity. So how might turtles respond to warmer beaches and warmer oceans as global temperatures rise? This is a great question that needs to be answered so as to ensure the existence of these vulnerable species is not risked.

Just to take you back and give you a sneak-peek of turtle’s life. Sea turtles use both marine and terrestrial habitats during their life cycles, the effects of climate change are likely to have a devastating impact on these endangered species. A rise in the sea level will impact sea turtle nesting beaches directly. Sea turtles' memories are "imprinted" with a magnetic map of the sandy beach where they hatched. This gives them the unique ability to return to that same site decades later to repeat their ancient nesting ritual. With melting polar ice caps and rising sea levels, these beaches are beginning to disappear. The direct impacts of sea level rise include losing beaches, ecologically productive wetlands and barrier islands.

An increase in nesting beach temperatures will also have an impact on sea turtles. Because sea turtles are reptiles, they rely on the temperature of the sand in which the eggs incubate to determine the gender of the hatchlings in a nest. Typically, the eggs in the lower, cooler, part of the nest will become males, while the eggs in the upper, warmer, part of the nest will become females. With increasing nest temperatures, scientists predict that there will be more female than male hatchlings, creating a significant threat to genetic diversity.

Warmer ocean temperatures are also likely to negatively impact food resources for sea turtles, and virtually all marine species. Coral reefs, which are an important food source for sea turtles, are in great danger. As a result of rising temperatures, coral reefs are suffering from a "bleaching" effect that kills off parts of the reef.

In my future blog post I will highlight to you the possible measures that need to be taken to address this issue of climate change and also how we are working in Lamu counter this major threat of climate change to help the turtles.