Grasslands and savannas (grasslands with trees) still cover a quarter of the earth’s land surface, and grazing by wildlife and livestock is the dominant land use on 90% of this biome. In addition, fire is an important process that has maintained grasslands and savannas for millennia.
Any
calculation of potential greenhouse gas emissions offsets by grassland and
savanna ecosystems must account for the effects of grazing and fire, yet their
combined effects on soil carbon are still poorly understood. Because of the
lack of good data, soil carbon offsets of CO2 emissions are not
certified by the European Climate Exchange, and allowed only for specific land
use practices in areas in the U.S. for which there are sufficient data. Thus,
data, simulation models, and remote sensing methods for assessing land use and
soil carbon balance constitute the critical technology for developing the
potentially lucrative market in soil carbon offsets, or “credits,” over vast
reaches of the earth’s surface.
The results lead to three major technological developments that facilitate the development of certified soil carbon offsets:
• Experimental data for how grazing and fire influence soil organic carbon from East Africa and around the world.
• Simulation models of soil carbon balance that correctly account for the effects of fire and grazing on a large landscape.
• Remote sensing methods that measure the critical variables affecting carbon balance – grazing intensity, standing biomass, and fire frequency.
The field experiment and simulation model illustrate the potential for offsetting CO2 emissions in the Serengeti and other tropical grasslands and savannas. Land use factors of grazing and fire explain 80% of the variation in the change in soil carbon observed in field experiments across a range of soil types, and a detailed simulation model predicts all of the major responses observed in the experiment across the Serengeti. New remote sensing techniques using visible, near-infrared, and thermal imagery allow us to monitor changes in grazing intensity, standing biomass and fire frequency.