|
Atmospheric concentrations of carbon dioxide (CO2),
methane, nitrous oxide, and other greenhouse gases have increased
substantially since pre-industrial times, and are expected to continue
their steep rate of increase if current emission patterns continue.
The major human source of greenhouse gas emissions is burning fossil
fuels. ERS research focuses on how changes in global climate may
affect both U.S. and world agricultural production, and investigates
those agricultural practices—such as conservation tillage or
winter cover crops—that can mitigate climate change by reducing
emissions or increasing carbon sequestration.
Fluctuations of CO2 and temperature
have roughly mirrored each other over the last 160,000 years. Over
the last century, the Earth has warmed about 1° F; the 1995
Report of the UN-sponsored Intergovernmental Panel on Climate Change
(IPCC) concluded that there is a discernible human influence on
global climate through greenhouse gas accumulations in the atmosphere.
ERS research on climate change has two major components: the longrun
impacts of greenhouse gas accumulation on agriculture throughout
the world, and the economics of options for
agriculture to reduce greenhouse gas accumulation.
Longrun Impacts on Agriculture
Farming occurs in those areas where potential agricultural productivity
is consistently high. Agricultural productivity, in turn, depends
on climate's influence on basic growing conditions such as air temperature,
soil temperature, and soil moisture. Another factor is the concentration
of carbon dioxide in the atmosphere, which affects crop productivity
through its influence on water use and photosynthesis. Changes in
climate and atmospheric concentrations of CO2, therefore,
would have longrun impacts on the world's ability to produce agricultural
commodities.
Farmers would respond to these changes in agricultural possibilities
by adopting alternative production systems (such as changing crop
and livestock varieties, employing irrigation, etc.) and by expanding
(or abandoning) agricultural lands. Agricultural land could expand
either in areas currently suitable for agricultural production or
into areas that are currently unsuitable but that develop productive
possibilities under global climate change. But adaptations would
not end there. The agricultural modifications would generate additional
responses from producers in other sectors as well as from domestic
and foreign consumers.
ERS's research on the longrun economic impacts accounts for both
the immediate effects on agricultural possibilities and the subsequent
economic responses, particularly in the agriculture sector. The
scope of ERS's research is also global in order to examine the distribution
of economic impacts round the world and its effects on international
trade. Recent analyses of projected increases in global temperature
of 2.8 to 5.2°C (5.0 to 9.4°F) indicate that climate change would
likely inhibit world agricultural production by the end of the 21st
century. Impacts on U.S. agricultural production, however, are indeterminant.
Other analyses, however, indicate that the direct growth-promoting
effects on crops generated by a 225-ppmv (parts per million by volume)
increase in atmospheric CO2 would likely boost world and U.S. agricultural
production. Both sets of analyses are limited in one or more crucial
ways. Hence, the net effects of greenhouse gas emissions on agriculture
remain uncertain.
Mitigation Options in Agriculture
The three major greenhouse gases emitted by agriculture are carbon
dioxide, methane, and nitrous oxide. U.S. agriculture represents
a small source of carbon emissions, but emits nearly three-quarters
of U.S. nitrous oxide emissions and about a third of methane emissions.
Mitigation options include better management of nitrogen fertilizers
(nitrous oxide) and livestock waste (methane). A number of farm
management practices could remove carbon from the atmosphere and
incorporate it into soils, thereby creating a carbon “sink.”
The international community is developing a system of commitments
toward emission reductions, linked with a series of flexibility
instruments to allow trades among parties. The economic impact on
the agricultural sector of any treaty would depend upon resolution
of a number of outstanding issues in the international negotiations
and the mix of domestic policies chosen to implement the treaty.
|
