NASA - National Aeronautics and Space Administration

Image above: National maps of net carbon sinks (red) and sources (blue) from 2000 to 2004, in units of billion metric tons of carbon per year predicted by NASA Ames computer modeling.
Image Credit: NASA Ames Research Center / Christopher Potter

Future climate scenarios of air temperature warming imply that ecosystems across the western United States will experience large carbon losses to the atmosphere and tree growth decline in the western United States, according to NASA Earth scientists.

The losses will occur "except in most isolated forest areas of the high mountain zones where the snow packs remain deep," said Christopher Potter, a scientist at NASA's Ames Research Center, Moffett Field, Calif.

Ecosystem carbon is the carbon that green plants remove from the atmosphere through photosynthesis, and which plants use to make roots, stems and foliage.

Scientists estimate potential losses of carbon across the western United States during a warmer and drier than average year will range from 10 to 40 grams of carbon per square meter, which may equal 10 percent of the total green plant production annually at many locations, according to Potter.

Carbon loss from green plants and other organic matter results from an earlier and warmer springtime climate in the mountainous West, which accelerates snow melt and water losses from the higher elevation ecosystems. More extensive wildfires later in the summer also lead to carbon loss.

Potter and research collaborators from California State University, Monterey Bay, and the University of Arizona, Tucson, will present their findings on Thursday, Dec. 13, 2007, at 11:15 a.m. PST during the annual American Geophysical Union fall meeting at San Francisco's Moscone West Convention Center.

"According to data from the MODIS sensor on NASA’s Terra satellite and Ames computer modeling, the forested mountain areas of the West still have the capacity to take up carbon from the atmosphere so long as wildfires do not increase notably," Potter also observed.

The scientists conducted their research during the last four years and used satellite data, information from ground-based instruments and readings taken from Earth-observing airplanes to arrive at a computer model for the study.

"The computer model we used reads in current satellite and climate data from sensors throughout the world and predicts past, present and future ecosystem carbon changes," Potter explained.

The researchers estimated past and future carbon balance for ecosystems in the western United States. Carbon balance is the difference between carbon sinks (such as carbon captured from the air by green plants) and carbon sources (such as factories and automobiles that burn fuel and put carbon into the air).

"We conducted this research because the influences of climate change on carbon held in ecosystem vegetation and soils — an important mechanism for offsetting fossil fuel carbon emissions — are not well understood, making projections in a changing climate quite uncertain," Potter explained.

According to Potter, scientists need to gather information about current and past places where carbon is trapped to provide a point of comparison for future actions.

"We cannot say yet with certainty what the ecosystem carbon effects will be on climate regionally, but we do know that land areas anywhere in the world that do not consistently sequester and store carbon over several decades will add notably to already increasing atmospheric carbon dioxide from fossil fuel burning, which is the main human factor contributing to global warming," Potter said.

John Bluck
NASA Ames Research Center, Moffett Field, Calif.
Phone: 650-604-5026
Email: jbluck@mail.arc.nasa.gov