Climate turns up heat on sea turtles

From an article by Moises Velasquez-Manoff in the Christian Science Monitor:

The ancient mariners need beach temperatures that are just right to hatch their eggs. If it's too warm, only females are born – and a species could vanish.

. . .Scientists worry that climate change, on top of ongoing stresses, could deal the final blow to these creatures. Ongoing threats include habitat loss, poaching, and being caught in nets and on hooks intended for other prey. Now, in a warming world, scientists also foresee stronger storms increasing erosion of the sandy beaches the turtles use to nest. Rising seas will inundate existing beaches, even as human development halts natural beach migration inland and upland. Shifting currents may alter the ocean's upwelling patterns, which turtles depend on for food.

Finally, there's global warming's most direct effect – more heat.

Turtles lack sex chromosomes. Their genes do not directly determine whether a hatchling comes out male or female. Instead, buried eggs take their cue from the ambient temperature. For leatherbacks, temperatures below 29.4 degrees C (85 degrees F.) produce a clutch that is mostly male; above that, it's mostly female. With a mere 2 degree C (3.6 degrees F.) increase, a nest will produce all females. A few degrees higher yet, and the "boiled" eggs don't hatch at all.

In order to maintain a viable breeding population, a cool, male-producing year has to come at least once every five to 10 years, says James Spotila, a professor of environmental science at Drexel University in Philadelphia. If male years begin to come only every 20 years because of climate change, the turtle could become extinct. . . .

Photo:(c) Wolcott Henry 2005/Marine Photobank