Global Warming Threatens Ocean Ecosystems

By Cat Lazaroff

WASHINGTON, DC, August 14, 2002 (ENS) - Climate change will create increasing challenges to U.S. coastal and marine ecosystems over the next century, warns a new report from the Pew Center on Global Climate Change. Temperature changes, altered patterns of rain and snowfall, and rising sea level are expected to upset the delicate balance of fragile coastal ecosystems.

The Earth's climate is expected to change must faster than normal over the coming decades due to the warming influence of human caused increases in greenhouse gas emissions. The world's oceans, which cover almost 70 percent of the planet's surface, are likely to show the effects of climate change in dramatic and devastating ways, the Pew Center warns.


Fragile ecosystems like this seagrass bed in the Florida Keys National Marine Sanctuary may suffer from changes in rainfall and runoff patterns. (Photo by Paige Gill, courtesy National Oceanic and Atmospheric Administration)
"Such high rates of change will probably result in local if not total extinction of some species, the alteration of species distributions in ways that may lead to major changes in their interactions with other species, and modifications in the flow of energy and cycling of materials within ecosystems," warns the new report, titled "Coastal and Marine Ecosystems and Global Climate Change: Potential Effects on U.S. Resources."

"Climate change could likely be the 'sleeper issue' that pushes our already stressed and fragile coastal and marine ecosystems over the edge," said Eileen Claussen, president of the Pew Center on Global Climate Change. "Particularly vulnerable are coastal and shallow water areas already stressed by human activity, such as estuaries and coral reefs. The situation is analogous to that faced by a human whose immune system is compromised and who may succumb to a disease that would not threaten a healthy person."

The report was prepared for the Pew Center by researchers from three universities, the National Center for Atmospheric Research and the International Pacific Halibut Commission. Based on current projections for climate change in the next century, the report explores the hazards that climate change may pose to marine life.

Critical coastal ecosystems such as wetlands, estuaries and coral reefs are particularly vulnerable to climate change, the report concludes. Such ecosystems are among the most biologically productive environments in the world, but their location at the interface between the land and ocean environments exposes them to a wide variety of human and natural stressors.


Warming seas may force some cold water species, like these walrus, to shift their ranges. (Photo by Captain Budd Christman, courtesy NOAA)
The added burden of climate change may further degrade these valuable ecosystems, threatening their ecological sustainability and the flow of goods and services they provide to human populations, the report warns.

Temperature changes in coastal and marine ecosystems will influence the metabolism of marine species, and alter ecological processes such as productivity and species interactions, the researchers said.

Species are adapted to specific ranges of environmental temperature, the report explains. As temperatures change, the geographic ranges of different species may expand or contract, creating new combinations of species that will interact in unpredictable ways. Species that are unable to migrate or compete with other species for resources may face local or global extinction.

Changes in precipitation and sea level rise will have far reaching consequences for the water balance of coastal ecosystems, the report notes. Increases in precipitation and runoff will increase the risk of coastal flooding, while decreases in precipitation may trigger droughts.

Meanwhile, sea level rise will gradually inundate coastal lands, the study warns. Coastal wetlands may migrate inland with rising sea levels, but only if they are not obstructed by human development.


Rising sea levels could inundate coastal marshes, forcing coastlines further inland and in many cases, eliminating marsh habitats. (Photo by Mary Hollinger, courtesy NOAA)
Climate change is also likely to alter patterns of wind and water circulation in the ocean environment. Such changes may influence the vertical movement of ocean waters, increasing or decreasing the availability of nutrients and oxygen to marine species.

Changes in ocean circulation patterns can also cause substantial changes in regional ocean and land temperatures and the geographic distributions of marine species.

The Pew Center notes that not all these potential effects can be predicted with confidence. The effects that are most certain have to do with how creatures and ecosystems will react to rising temperatures and sea levels. Predictions about temperature's influence on interactions among species, water circulation patterns, precipitation, wind patterns, and the frequency and intensity of storms, are less certain, the report's authors caution.

Still, governments can not afford to wait for more certainty before taking action to reduce greenhouse gas emissions and combat global warming, says the Pew Center's Claussen.


Coral reefs, the nurseries of many marine species, may be killed by higher temperatures, or by a lack of sunlight as sea level rises. (Photo courtesy Florida Keys National Marine Sanctuary)
"It is increasingly apparent that the United States needs a strategy to address the very real threat of climate change," said Claussen. "The longer we wait, the graver the risks - and the cost of averting them."

The current report is the eighth in a series of Pew Center reports examining the potential impacts of climate change on the U.S. environment. Other Pew Center reports have focused on domestic and international policy issues, climate change solutions, and the economics of climate change.

The full report is available at: