|
A win-win war on climate change
Better farming practices could help agriculture bury about 10 percent of atmospheric carbon from emissions caused by human activity over the next 25 years -- while improving soil, crop and environment quality, slowing erosion and desertification, and enhancing biodiversity. p Agroforestry
needs careful management, but has excellent
potential for combining carbon sequestration with
productive land use. Here, millet is grown under
acacia trees in Mali.
(FAO/15859/R.Faidutti) Carbon dioxide is the most prominent "greenhouse" gas. Carbon sequestration can be used to partially offset a country's carbon dioxide emissions, helping it meet its commitments under the Kyoto Protocol, the mechanism for implementing the UN Framework Convention on Climate Change. The Protocol's Clean Development Mechanism allows developed countries to offset some of their emissions by funding climate-friendly projects in the developing world. This offset process, in its infancy, will eventually "credit" agricultural development that increases plant matter, and thus carbon sequestration. Reversing the damage "Forests store more carbon than farmland, but farmland has the potential to increase its carbon storage, whereas mature forests may do so at lower rates," says Jacques Antoine, an FAO soil scientist who worked on the report. Increasing soil organic matter in farmland also improves soil structure, allowing water to reach the crop's roots rather than running off the surface, taking precious topsoil with it. Reducing or eliminating tillage can protect soil organic matter. So can leaving crop residues in place after harvest. A technique known as conservation agriculture integrates all of these practices. But crop residues may be needed for animal feed. Or leaving them on the ground may delay re-sowing. The economics of farming are harsh, especially in the developing world. So the report looks at the big picture for several different farming systems, such as agroforestry, grazed grassland and arable land. Bury it. Measure it
Grasslands could be as useful in practice. The world's estimated 3.2 billion hectares of grasslands could store as much soil carbon per hectare as forests. But about 70 percent are degraded, often through overgrazing. Stopping overgrazing is the key, followed perhaps by improving degraded grassland by planting it with legumes or grass species with deeper root systems. These activities could increase carbon sequestration -- and provide more sustainable grazing, and thus more income. Still, arable land remains crucial. Buildup of soil organic matter can be encouraged through better crops and agronomic practices, including minimizing tillage, leaving crop residues in place, mulching and using manure and even sewage sludge as fertilizer. Before any of this can figure in carbon audits, researchers need better measurement tools. They must assess when, how and where carbon is best sequestered, the success of current afforestation and rehabilitation projects, and how much soil organic matter is built up in plant roots. And they need a mass of other scientific and socio-economic data. An FAO expert in
Bolivia measures grass that has been planted as
pasture for cattle. With care, land use of this
type can sequester a lot of carbon -- and support
animals at the same time. (FAO/20889.1/J.Spaull)
True green revolution "Agriculture in the developing world can do much to mitigate climate change while becoming more sustainable and productive," says Mr Antoine. "Soil carbon sequestration for improved land management is the first route map towards that goal." 28 March 2002
Read our most recent articles on: Related links
Comments?: Webmaster@fao.org |
