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For more information on these science news and feature story tips, please contact the public information officer at the end of each item at (703) 292-8070. Editor: Peter West Contents of this News Tip:
Earth's Ecosystems Slowed Greenhouse Gas Buildup in 1990s; Climate Change Could Speed ItEarth's terrestrial ecosystems absorbed all of the carbon released by deforestation and some of the carbon emitted by fossil-fuel burning during the 1990s. But those ecosystems cannot be relied upon to nullify carbon’s influence on global climate change in the future, according to researchers funded partly by the National Science Foundation (NSF) and affiliated with the National Center for Atmospheric Research (NCAR) in Boulder, Colorado. Land-use changes in the Northern Hemisphere have been partly responsible for reducing the amount of carbon released into the atmosphere during the 1990s. In the U.S., trees and other plants thrived on abandoned agricultural land, while a reduction in the number of fires allowed forests to spread. Growing plants use large amounts of carbon dioxide (CO2). Enhanced plant growth spurred by increasing carbon dioxide and nitrogen deposits also helped clear the air of CO2 buildup. Carbon accumulates at higher rates in intensively managed ecosystems and those recovering from disturbance, the researchers note. But, stresses NCAR scientist David Schimel, "we could easily see this robust transfer of carbon out of the atmosphere and into land-based ecosystems that occurred in the 1990s slow down in the future." He adds that "eventually, new trees and grasses reach maturity and soak up less carbon dioxide. Similarly, there's a limit to how much forests can fill in and spread, even with successful fire suppression." [Cheryl Dybas] Old Corn Critical to Crop Yield, Student Model SuggestsOld corn crops, far from being outmoded by genetic engineering, should be preserved for their potential value as a tool in helping genetically engineered stocks fight insect infestation, according to mathematics student Nicholas Record. A graduate student at New York’s University of Rochester, Record developed a math-based model of how the European Corn Borer, a major threat to Midwestern crops, could be expected to evolve in response to genetically altered crops. Scientists have developed a genetically altered corn that is resistant to the borer. But there is concern that the borer will evolve to overcome this resistance. The current preventative strategy involves planting a portion of the acreage with the original corn. Record's model predicts that the current strategy will not prevent the insects from overcoming the resistance of new genetic strains, and suggests that a better strategy to guarantee long-term high crop yields includes periodically planting the original corn exclusively. Record developed his theory while participating in the NSF’s Research Experience for Undergraduates (REU) program under the tutelage of NSF-supported mathematician Timothy Pennings of Hope College, in Holland, Michigan. [Amber Jones] Accumulated Changes Threatens Delicate Balance, Courts Ecosystem CatastropheSubjected to decades of gradual human modification, many of the world's natural ecosystems - from coral reefs and tropical forests to northern lakes and forests - appear susceptible to sudden catastrophic ecological change, according to Stephen Carpenter, an NSF-funded limnologist at the University of Wisconsin at Madison. As scientists have assessed change over time and over entire ecological regimes, they have gradually become aware that stressed ecosystems, given the right nudge, are capable of slipping rapidly from a seemingly steady state to something entirely different, Carpenter explains. "We realize that there's a common pattern we're seeing in ecosystems around the world," he says. "Gradual changes in vulnerability accumulate and eventually you get a shock to the system - a flood or a drought - and boom, you’re over into another regime. It becomes a self sustaining collapse." Most ecosystems face a steady diet of change, whether from increasing nutrient levels or a ratcheting up of human impacts. Anticipated changes in global climate are expected to add to what now seems to be a far more precarious ecological situation than scientists had previously imagined. "All of this is set up by the growing susceptibility of ecosystems," Carpenter says. "A shock that formerly would not have knocked a system into another state now has the potential to do so. In fact, it's pretty easy." [Cheryl Dybas]
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