Agriculture is a big contributor to climate change. According to the International Panel on Climate Change (IPCC, Fourth Assessment Report, 2007) this accounts to 10-12% on all anthropogenic greenhouse gas emissions.
Use of synthetic nitrogen fertilizer is the biggest contributor to climate change in agriculture through the very potent greenhouse gas N2O (nitrous oxide). Enteric fermentation is second in the row because of cows and sheep producing CH4 (Methane) due to anaerobic fermentation in their stomachs.
A very important source connected to agriculture – and even bigger in size- needs mentioning, the conversion of land. Mostly extensive grasslands are converted to crop land (yearly 6 million of hectares) and the conversion of forests to cropland (yearly 7 million of hectares). The loss of CO2 above-ground (trees and plants) and underground (soil organic matter) is enormous. Especially peat soils carry huge loads of soil organic matter which releases under crop growing in the following decades.
The only way stopping releasing climate gases by land conversion is stopping land conversion and stopping forest destruction. This means our consumption, especially in the rich countries, has to be lowered to stop the pressure on newly converted land. The consumption of meat needs to be lowered because meat production heavily draws on feed production and on huge areas of land (like soybeans and corn), as well as the production of biofuels needs to be abandoned. (huge land use; no real carbon gain).
The positive part of the story is agriculture also possess a big mitigation potential.
The Fourth Assessment of the IPCC (2007) recommends mitigation measures on,
- crop rotation and crop design
- nutrient management
- livestock growing
- (maintaining) fertile soils.
In the box below the most important examples of practices and methods for these four areas of mitigation are shown. These measures and practices are essentially arguing for a low-input agriculture, conservation measures at soil level and recycling of nutrients. These kind of measures are combined in a system-approach called Integrated Production (IP, also IPM or ICM), integrated crop management including Organic Production.