When leatherback（棱皮龟） turtle hatchlings dig out of their nests buried in the sandy Playa Grande beach in northwest Costa Rica, they enter a world filled with dangers. This critically endangered species faces threats that include egg poaching and human fishing practices. Now, Drexel University researchers have found that the climate conditions at the nesting beach affect the early survival of turtle eggs and hatchlings. They predict, based on projections¹ from multiple models, that egg and hatchling survival will drop by half in the next 100 years as a result of global climate change. "Temperature and humidity inside the nest are significant factors affecting egg and hatchling survival," said Dr. James Spotila, the Betz Chair Professor of Environmental Science in Drexel's College of Arts and Sciences, and senior author of the study reported May 23 in the journal PLoS ONE. Spotila and colleagues, including lead author Dr. Pilar Santidrian Tomillo of Drexel, therefore examined the relationship between regional climate patterns with leatherback turtles' nesting success over six consecutive² nesting seasons at Playa Grande. This beach is the major nesting site for leatherback turtles in the eastern Pacific Ocean, containing more than 40 percent of nests.

"We have discovered a clear link between climate and survival of this endangered sea turtle population," said Spotila.

The turtles' hatching success and success emerging from the nest was significantly correlated with weather patterns associated with the El Niño Southern Oscillation (ENSO). ENSO is an irregular pattern of periodic climate variation, shifting between "El Niño" periods with warmer sea surface temperature conditions in the eastern tropical Pacific, and "La Niña" conditions with cooler sea surface temperatures, with ENSO neutral conditions in between. The El Niño cycle is known to influence many ecological³ processes that vary from location to location.

The researchers found that warmer, dryer⁴ El Niño conditions were associated with significantly higher mortality for eggs and hatchlings. Using projections of global climate change due to global warming over the next 100 years, they predicted that El Niño conditions will become more frequent and hatchling success will decline throughout the 21st century at Playa Grande and other nesting beaches that experience similar effects.

As climate conditions change, leatherbacks nesting at Playa Grande cannot move to other beaches. Spotila noted⁵ that the beach characteristics and off-shore ocean currents move hatchlings to feeding grounds on a kind of "hatchling highway" that makes Playa Grande an optimal⁶ nesting location for leatherbacks that other beaches cannot replace. Spotila was senior author of a modeling study demonstrating this pattern, led by Dr. George Shillinger of Stanford University and published in the June 2012 issue of Proceedings⁷ of the Royal Society B.

Spotila has conducted research with nesting leatherback turtles at Las Baulas Park in Costa Rica, where Playa Grande is located, for 22 years. He recently joined the faculty⁸ of Drexel's new Department of Biodiversity, Earth and Environmental Science (BEES), formed as a result of the University's unique affiliation⁹（友好关系） with the Academy of Natural Sciences, the oldest natural history museum in the U.S. and a world leader in biodiversity and environmental research.