Climate change threat to animal habitats

The top ocean predators in the North Pacific could lose as much as 35 percent of their habitat by the end of the century as a result of climate change, according to a study published yesterday in the journal Nature Climate Change.

The analysis, conducted by a team of 11 American and Canadian researchers, took data compiled from tracking 4,300 open-ocean animals over a decade and looked at how predicted temperature changes would alter the areas they depend on for food and shelter. Some habitats could shift by as much as 600 miles, while others will remain largely unchanged, the scientists found, and these changes could affect species in different ways.

For some key species already facing threats, including blue whales and loggerhead turtles, this will make the food that sustains them more elusive.

"They'll have to travel farther and farther every year just to get to their food," said Elliott Hazen, the study's lead author and a scientist with the National Oceanic and Atmospheric Administration's Southwest Fisheries Science Center.

Some species with a relatively narrow temperature range -- such as salmon, blue sharks and mako sharks -- fared poorly as well.

At the same time, some highly mobile species such as tuna and seabirds may benefit from the changes because they will either be able to adjust more easily or have wider foraging opportunities.

The scientists identified key habitat areas by using satellite measurements of sea surface temperature and chlorophyll-a, which indicates an area's productivity, along with migration patterns charted by the Tagging of Pacific Predators project. Using projections by the UN Intergovernmental Panel on Climate Change that global temperatures could rise between 1.8 to 10.8 degrees by 2100, the researchers modeled how the changes would affect habitat.

The North Pacific Transition Zone, from California to Japan, where cold, nutrient-rich polar water comes into contact with warmer, nutrient-poor water, will shift the most dramatically, as 600 miles to the north in most seasons. This corridor could lose as much as 20 percent of its species diversity.