February 28, 2007
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Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999
FROM VOLUME 11, NUMBER 10, OCTOBER 1998
Climatic Change devoted a special issue to the topic of the
mitigation of greenhouse gases by the agricultural sector:
Mitigation of Greenhouse Gas Emissions by the Agriculture Sector,
N. J. Rosenberg (Pacific Northwest National Laboratory, Washington, D.C.,
20024), C. V. Cole, Keith Paustian,Clim. Change 40 (1),
The editors survey and summarize the articles in this special issue and
conclude that emissions of N2O and CH4 can be
substantially reduced by practices that simultaneously increase
productivity and that the sink for carbon in soils can be substantially
increased. They also feel that further improvements in mitigation
techniques could be developed with additional research. A major problem is
how to encourage the adoption of mitigation techniques. They point out
that greater attention must be devoted to understanding socioeconomic and
political impediments to that adoption and urge the IPCC to place greater
emphasis on this aspect of the problem.
Assessing and Mitigating N2O Emissions from Agricultural
Soils, A. R. Monsier (USDA/ARS, Fort Collins, CO, 80521) et al.,
Clim. Change 40 (1), 7-38 (1998).
Agricultural systems are estimated to produce about one-fourth of global
N2O emissions. Methods that could mitigate these emissions
include increasing the productivity of agricultural lands, lengthening the
rotation times of shifting agriculture, managing grasslands, incorporating
crop residues into the soil, using crop residues for household fuel,
shifting production to tree crops, altering the methods of fertilizer
application, matching nitrogen supply with demand, managing mineral
nitrogen during fallow, applying less fertilizer more frequently during
cropping, supplying fertilizer in irrigation water, using
controlled-release fertilizers, using nitrogen-transformation fertilizers,
and managing waste more efficiently. Most of these practices would
increase agricultural productivity as well as minimize the introduction of
N2O into the atmosphere.
Mitigating Agricultural Emissions of Methane, A. R. Monsier
(USDA/ARS, Fort Collins, CO, 80521) et al., Clim. Change 40
(1), 39-80 (1998).
Ruminant animals, flooded rice paddies, animal wastes, and biomass
burning produce about one-third of global methane emissions. Mitigative
measures include improving the nutrition of animals with cereal grains,
introducing genetic improvements, employing bovine growth hormone,
improving feed formulations, modifying rumen fermentation through
biotechnological approaches, adopting manure-management and -treatment
practices (e.g., covered lagoons and digesters), managing water and
nutrients during rice production, selecting low-emission rice cultivars,
adopting new rice-cultivation practices, increasing the productivity of
agricultural lands, lengthening the rotation times of shifting
agriculture, managing grasslands, incorporating crop residues into the
soil, using crop residues for household fuel, and shifting production to
Possibilities for Future Carbon Sequestration in Canadian
Agriculture in Relation to Land Use Changes, J. Dumanski (Centre for
Land and Biological Resources, Research Branch, Agriculture and Agri-Food
Canada, Ottawa, Ontario, K1A 0C6, Canada) et al.,Clim. Change 40
(1), 81-103 (1998).
Several strategies for increasing carbon sequestration in agricultural
soils in various regions of Canada were assessed. The most effective
options are reducing summer fallow, converting fallow areas to hay or
continuous cereals, fertilizing to ensure the nutrient balance, and
adopting soil-conservation measures. Increased sequestration could be
achieved in all regions of Canada, but the greatest gains could be made in
areas with Chernozemic soils. Up to 75% of the total agricultural CO2
emissions in Canada could be sequestered, but only for a limited time.
Carbon Sequestration and Turnover in Semi Arid Savannas and Dry
Forest, H. Tiessen (College of Agriculture, University of
Saskatchewan, Saskatoon, Canada, S7N SA8) et al.,Clim. Change 40
(1), 105-117 (1998).
About 40% of the land in northeast Brazil has near-climax vegetation,
less than 10% is planted annually, and about 35% is subject to shifting
cultivation of five-year duration with >20-year recovery. Vegetative
litter is partly decomposed and partly eaten by animals, resulting in low
soil carbon levels; and cultivation depletes about 50% of these already
low levels. In western Africa, up to 70% of the land is under agricultural
management that returns very little carbon to the soil. Overgrazing and
intensive collection of fuel wood have further degraded the soil, and
short fallow periods on agricultural lands have led to serious declines in
soil carbon stocks. In both these regions, greater sequestration could be
effected by increased crop production under suitable rotations, longer
fallowing, improved animal husbandry, and limitation of biomass burning.
Carbon Dioxide Fluxes and Potential Mitigation in Agriculture and
Forestry of Tropical and Subtropical China, Li Zhong (Institute of
Soil Science, Academia Sinica, Nanjing 210008, China), Zhao Qi-Guo,Clim.
Change 40 (1), 119-133 (1998).
Of the tropical and subtropical areas in China, about 40% is forest, 20%
is cropland, and 20% is wasteland. Increasing productivity, boosting
carbon inputs to the soil, and converting wasteland to agricultural
production could sequester an estimated additional 1.9 TgC/y, and
conversion of wasteland to fuel wood plantations and current forestry
practices could sequester >30 and 7 TgC/y, respectively.
Mitigation by Agriculture: An Overview, K. Paustian (Natural
Resource Ecology Laboratory, Colorado State University, Fort Collins, CO,
80523) et al.,Clim. Change 40 (1), 135-162 (1998).
CO2 emissions could be substantially reduced by reducing the
conversion of tropical lands to agriculture, and an important method of
doing that is the improvement of the productivity and sustainability of
existing lands under cultivation. It is estimated that better soil
management, restoration of degraded lands, setting aside of surplus
agricultural lands, and restoration of former wetlands could sequester up
to 0.9 PgC/y. Reducing direct agricultural emissions would produce modest
mitigation, but the possibility of offsetting fossil-fuel consumption with
biofuels could produce substantial mitigation.
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