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More tools may be at hand to combat global warming

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January 18, 1999 Share This!

ST. MICHAELS, Md. — Farms, forests and grasslands around the world can play an important role in combating global warming in the 21st century by removing carbon from the atmosphere and storing (sequestering) it in the soil. That was the major conclusion of a recent workshop in St. Michaels, Md., organized by the Department of Energy's Pacific Northwest National Laboratory, DOE's Oak Ridge National Laboratory and the Council for Agricultural Science and Technology.

Scientists have calculated that over the next 50 to 100 years, agricultural lands alone have the potential to remove anywhere from 40 to 80 billion metric tons of carbon from the atmosphere.

"By making modest changes in farming and forestry practices, plants and soils can be used much more efficiently to remove carbon dioxide from the atmosphere. This not only cleans the atmosphere but increases organic matter in the soil where it is beneficial," said Cesar Izaurralde, staff scientist with the global climate change group at Pacific Northwest.

The increase in carbon dioxide in the atmosphere is believed widely to be the chief cause of global climate change.

Workshop participants also concluded that:

  • There are practical and economically viable farming methods that increase carbon storage in soil, but research is needed to develop methods that increase the amount stored and the length of time it remains in the soil.
  • It is possible to monitor changes in soil carbon content, but current methods are crude and expensive. Technological development could provide new and widely applicable methods at a reasonable cost.
  • There are vast areas of degraded and decertified lands throughout the world, many in developing countries where improvements in rangeland management, dryland farming and irrigation can add carbon to the soil. These changes also will stabilize the soil against erosion and increase its fertility and productivity.

Deforestation and the use of fossil fuels release about eight billion metric tons of carbon into the atmosphere annually in the form of the greenhouse gas carbon dioxide. Most is removed from the atmosphere by plants or by the world's oceans, but a significant portion remains airborne. Consequently, atmospheric carbon dioxide continues to increase at the rate of 3.5 billion tons every year. Reductions can be achieved by applying tried-and-true land management practices such as reduced tillage, increased use of rotational crops such as alfalfa, clover and soybeans and by an efficient return of animal wastes to the soil. Forests and grasslands afford additional capacity for carbon sequestration when established on former crop lands.

"Changing farming practices won't solve the problem, but it will buy us time until technology is on line to reduce the generation of harmful greenhouse gases," said Dr. Norman Rosenberg, chief scientist with the global climate change group at Pacific Northwest.

"When croplands are planted to perennial grasses under the Conservation Reserve Program, as much as a half ton or more of carbon per acre can be returned to the soil annually. And when agricultural land reverts to forest, soil carbon can accumulate at even greater rates, especially in the tropics," Rosenberg said.

The recent Kyoto Protocol to the United Nations Framework Convention on Climate Change would, if ratified, require developed nations to reduce their net carbon emissions in the period 2008-2012 to less than was emitted in 1990.

Not everyone, however, supports using soil carbon sequestration in the calculations that are used to determine a country's net carbon emissions.

"I think one reason for opposition to this idea is a perception that it will be difficult, if not impossible, to verify claims from around the world that carbon actually is being sequestered in soils. This is an issue that we will have to resolve," said Wilfred "Mac" Post of Oak Ridge.

Uncertainty about the costs, benefits and risks of new practices will make producers reluctant to adopt new technologies to increase carbon sequestration. However, Drs. Gregg Marland of Oak Ridge and Bruce McCarl of Texas A&M University said that financial incentives could increase the adoption of such practices and potentially provide an addition to farmer income. This could be accomplished through government payments, tax credits and/or emissions trading within the private sector. They said programs designed to accomplish these objectives should be explored.

The workshop was attended by nearly 100 U.S. and Canadian scientists, practitioners and policy-makers representing agricultural commodity groups and industries, Congress, government agencies, national laboratories, universities and the World Bank. They addressed scientific and policy problems associated with soil carbon sequestration. Support was provided by the Environmental Protection Agency, the U.S. Department of Agriculture, the Department of Energy, the Monsanto Company and NASA.


Tags: Energy, Environment, Fundamental Science, Emissions, Climate Science

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