Image Source: KevinLallier
Dear Pablo: What role does agriculture play in combating climate change and how will climate change affect it?
Greenhouse Gas Emissions From Land-Use Changes
The very first effect that humans had on the climate was through agriculture. As humans traded in their hunter/gatherer way of life for one based on farming and livestock, forests and grassland were cleared to make room for crops and domesticated animals. These land-use changes grew from near-zero over 8,000 years ago to today's 4+ billion acres of cultivated land. While the initial impact was relatively minor compared to today's industrial greenhouse gas emissions, it was still significant enough to prevent an ice age
Greenhouse Gas Emissions From Fertilizer and Biocide Use
Since the industrial revolution, the impacts of agriculture--which were mainly limited to changes in land-use and the methane emissions from ruminant animals--expanded. The advent of synthetic fertilizer, particularly nitrogen-based, increased the amount of nitrous oxide emissions from soil. Nitrous oxide, or N2
O, also known as "laughing gas" is 310 times as potent as carbon dioxide at trapping the earth's heat. The use of various biocides has killed natural soil biota that normally fix nitrogen in the soil and has lowered soil quality in general, requiring even more synthetic additives.
Greenhouse Gas Emissions From Mechanization and Livestock
Naturally, the mechanization of farm equipment contributed combustion emissions from fossil fuels-- although I have heard arguments that the increased productivity from using a tractor makes it more environmentally friendly than having to grow feed for horses or other beasts of burden (perhaps a future topic). And finally, the increased appetite for meat, and the widespread use of CAFOs
has increased the amount of methane produced by livestock
to where it constitutes the largest component of anthropogenic (human-caused) methane emissions.
Agriculture As A Solution To Climate Change
Perhaps someone should tell Midwestern House and Senate members that the sale of carbon credits could net farmers a great deal of additional income. There are several carbon credit-generating opportunities, as promoted by the National Farmers Union
: practicing no-till agriculture, converting cropland to grass, sustainable management of natural grasslands, planting trees, and manure management that captures methane
Storing Carbon In The Soil
In addition to restoring soil biota that fixes nitrogen and composting, agricultural waste carbon from woody biomass can also be stored in the soil. The process of producing biochar involves gassifying woody biomass with high heat in the absence of oxygen, which turns volatile components into a gas that can be transformed into liquid fuels similar to gasoline, and results in a form of charcoal that is almost entirely carbon. Biochar, when added as a soil amendment, can hold soil moisture, support soil biota, and increase the soil's carbon content for many years, even centuries. Like so many other potential solutions, Biochar has its supporters
Pablo Päster is a weekly columnist for TreeHugger.com, an experienced greenhouse gas engineer and the Senior Environmental Program Manager at Hara Software. Send your questions to Pablo(at)TreeHugger.com and connect to his RSS feed.
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