Climate change will shift marine predators’ habitat, study says
By Juliet Eilperin (The Washington Post) - September 24, 2012
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 Sunday 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 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 (TOPP) project. Using U.N. Intergovernmental Panel on Climate Change projections that global temperatures could rise 1.8 to 10.8 degrees by 2100, the researchers modeled how these changes would affect habitat.
The North Pacific Transition Zone — which marks where cold, nutrient-rich polar water comes into contact with warmer, nutrient-poor water — will shift the most dramatically, by as much as 600 miles to the north during most seasons. According to the paper, this major migration corridor, which stretches from California to Japan, could lose as much as 20 percent of its species diversity.
By contrast, the California Current, which runs along North America’s western coast, will not be affected, because the upwelling of cold, nutrient-rich water will continue to occur and will stay largely in place.
“It will act like a buffer to climate change,” Hazen said in an interview. “That’s a kind of saving grace to the central California environment.”
Larry Crowder, a co-author of the study and science director of Stanford University’s Center for Ocean Solutions, wrote in an e-mail that “five years ago this work could not have been done.”
“The confluence of an amazing tagging data set, remote sensing, and cutting edge modeling allows us to predict dynamic ocean habitats for large ocean predators for the first time,” he wrote, adding that scientists can now “design mobile marine protected areas that can protect threatened predators while minimizing impacts on fisheries.”
Hazen warned that policymakers need to take advantage of the new findings, rather than imposing protections on a fixed area in perpetuity. “If we’re going to create a marine protected area and the habitat disappears, we’re going to be making some pretty big mistakes.”