Global Warming

How will Global Warming affect sea turtles?

The impact of such phenomenal climate change pervades every level of the environment. An increase in temperature of just 1ºC from global warming could eliminate the birth of male sea turtles, according to the recent study from the University of Exeter. A rise of 3º could lead to extreme levels of infant mortality and declines in nesting beaches across the USA and globally.
Changing the sex ratio of sea turtles will make saving these enigmatic creatures from the edge of extinction even harder...

Cool beaches produce mostly male hatchlings, while warm beaches produce predominantly females. The shifting ratios moving towards a ‘feminising’ of sea turtle populations are a serious concern for conservation efforts. Although females already deal with a shortage of males, a ratio of 1:4 male to female is not something that can be easily compensated for.
With rising global temperatures some nesting beaches will turn from incubators to lethal ovens with temperatures exceeding the 34°C limit. Decreases in hatchling success and emergence will pose follow-on impacts through the whole sea turtle population as genetic stock continues to diminish. Whether sea turtles will respond to climate change through changes in the distribution of nesting and changes in associated migratory routes remains an uncertainty.

Loss of nesting and feeding habitats due to sea-level rise is especially a threat in low-lying islands where nests can become easily inundated. Climate-related increases in wave energy and storm events may erode nesting beaches and reduce egg survival. While changes in food resources with shifting currents influencing upwelling patters will inevitably increase the pressure on sea turtle populations even further.

Six Major Impacts of Climate Change on Sea Turtles
Long term survival?

Natal Beaches
Marine turtle populations may return to the same breeding area while environmental conditions remain stable but they may shift to new breeding sites in response to changing environmental cues such as sea temperature, beach temperature, beach stability and proximity to suitable ocean current for dispersing hatchlings to pelagic foraging areas.

Sea turtles are characterized by temperature dependent sex determination – cool beaches produce male hatchlings, warm beaches produce mostly females. With increasing temperatures there is likely to be a feminizing of marine turtle population. Over the last 50 years some critical nesting beaches have already shifted into totally female producing. While turtle populations appear to function successfully with an excess of females (male:female = 1:2 to 1:3), there probably should be concerns if the regional sex ratio for the species approaches 1:4 male to female.

Impact on nesting beaches
Turtles are expected to be little affected by sea level rise. Their nesting should occur above the new tide levels. But on low elevated sand beaches the impact of erosion and flooding of the nesting habitat is expected to cause increases in egg mortality and eventually loss of some nesting areas.

Pelagic Environment
The location of plankton rich zones of the open ocean are expected to vary in location between years in response to climate change. Post-hatchlings migrations should change in response to changes in distribution of water masses and plankton, and the positive or negative aspects are difficult to predict at present.

Impact on coastal foraging habitat
Climate change cause hot summers, intense storms and rainfalls. Hot years are causing coral bleaching and negatively impacting coral reefs. Intense storms cause structural damage to coral reefs and erosion of seagrass pastures. While the food resources are depleted there will be reduced growth rates of immature turtles, reduced levels of adult turtles that prepare for breeding migrations and increase in mortality of green turtles in the following months.

Global warming may engender algal blooms and contribute to epizootics. Mass die-offs of marine mammals have increased, and where the cause has been viral, environmental factors have contributed to the outbreaks or reduced the ability of the animals to fend off the illnesses.

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