Climate Change
Agriculture and forestry together contribute approximately 24% of the global greenhouse gas emissions (IPCC, 2014). This presents a large impact from crop and livestock production and deforestation. If we break it down a bit further, there are many agricultural activities that contribute to greenhouse gas emissions, and therefore, to climate change. Emissions occur from the cultivation of soil, which releases carbon dioxide (CO2); from nitrogen fertilizers, which release nitrous oxide (N2O) emissions (see other concerns about nitrogen fertilizers); and from – this is an important one – methane (CH4) released by livestock belching during digestion and from their decomposing manure during storage.
However, it is also important to note that agriculture sequesters, or stores, some of these harmful emissions as well. Plant (including tree) roots and other organisms in the soil can hold onto carbon and nitrogen and keep them from moving into the atmosphere. There are practices (see Practices in Sustainable Agriculture) that enhance the capacity of agriculture to act as a ‘sink’ or storage for some greenhouse gases, rather than a source of them.
Agriculture is also increasingly impacted by climate change. This presents both opportunities and challenges. The opportunities include:
- a longer growing season in more northern areas, resulting in more options for crops for farmers in those areas and greater flexibility when planning; and,
- greater productivity of some crops in some cases, due to more favourable growing conditions.
The challenges of climate change outweigh any potential benefits, however. In general, these challenges include:
See this report, for how climate change may impact agriculture in Ontario.
- increases in the number and intensity of agricultural pests and diseases as conditions become more favourable for their survival and spread to new locations;
- increases in the frequency and severity of severe weather events resulting in damage and loss of crops; and,
- more droughts and higher temperatures that cause crop losses and change the potential of some land for agricultural production.
Farmers must not only think about mitigating their effects on climate change by reducing their emissions and finding ways to act as a sink for greenhouse gases, but also how to adapt (change their practices) to deal with the inevitable changes in the climate. These adaptations form an important part of working towards agricultural sustainability, and are described in the next section.
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