WASHINGTON, DC – Although no one knows the ultimate effects of climate change on marine ecosystems, scientists know enough about the oceans to proceed with adaptation, researchers reported Saturday at the annual meeting of the American Association for the Advancement of Science. And while many previous studies have focused on minimizing detriments to single species of economic importance, future efforts should shift to preserving ecosystems and their capacity to adapt, they suggest.
While many people recognize the warming effects of climate change on Earth’s atmosphere, the oceans are sucking up heat too. Only 4 percent of the excess energy absorbed by the planet in the past 40 years has gone into heating the atmosphere, but 84 percent has gone into the oceans, a larger and much more effective reservoir of heat, said Chad English, director of science policy outreach at the Communication Partnership for Science and the Sea (COMPASS) in Silver Spring, Maryland. (The rest of that energy imbalance has gone into warming Earth’s landmasses and melting ice, he notes.) Meanwhile, oceans are acidifying (by the end of this century, they’ll reach a pH lower than any experienced in the last 20 million years), sea levels are rising, and waves are getting bigger, driven by faster winds. The changes seen so far are just a preview of coming attractions, he suggests: “We’ve only seen [Earth’s] transient response to warming, and we don’t yet know at what point ecosystems will break down.”
Indeed, a wide variety of holes exist in scientists’ knowledge about when —and how — ecosystems will respond to climate change. While many studies have assessed the individual effects of warmer waters, increasing levels of ocean acidity, and lower levels of dissolved oxygen on various marine species, the combined effects of multiple stressors are largely unknown, said James Barry of the Monterey Bay Aquarium Research Institute in Moss Landing, California.
Looking to save ecosystems by preserving a single species of importance probably won’t work, said Nancy Knowlton, a marine biologist at the Smithsonian Institution’s National Museum of Natural History in Washington, D.C. Such a “California condor” approach – a massive effort dedicated to preserving just one, usually charismatic species – ignores the fact that ecosystems are finely-tuned biological networks composed of numerous interacting species. In the case of coral reefs, Knowlton’s specialty, those ecosystems are home to more than 1,000 species of corals and between 1 million and 9 million species of fish and other organisms.
While researchers are now developing detailed simulations of many marine ecosystems, models that include anything other than the lowest levels of the ocean’s food chain won’t be ready for three to five years, said Anne Hollowed, a fisheries ecologist with the National Oceanic and Atmospheric Administration in Seattle, Washington. And when those models eventually arrive, scientists will also need to consider factors such as fishing pressure and how climate change will cause shifts in the habitats suitable for various species.
A far better approach than saving a few keystone species would be to preserve an entire ecosystem’s ability to adapt, says Andrew Rosenberg of Conservation International in Arlington, Virginia. While long-term efforts to mitigate climate change might address carbon dioxide emissions, the root cause of climate change, in the short term people can preserve the ocean’s biodiversity at local levels by reducing overfishing, nutrient runoff and pollution. “Reasonably simple things can be done, and many steps can be taken before the results of detailed [ecosystem] modeling are in,” he said.
“The choices we make in the next decade will be with us for millennia,” said English. “Today’s choices affect tomorrow’s options.”