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
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.
Major Impacts of Climate Change on Sea Turtles
Long term survival?
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.
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.
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
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.
text is available in http://www.cms.int/publications/pdf/CMS_CimateChange.pdf