New USDA Assessment Addresses Climate Change & Agriculture

By: Garry Stephenson

“There is a robust scientific consensus that human induced climate change is occurring.” Thus begins a new US Department of Agriculture assessment of the impacts of climate change on agriculture. Some overarching conclusions of the assessment:

• Climate changes – temperature increases, increasing CO2 levels, and altered patterns of precipitation – are already affecting U.S. water resources, agriculture, land resources, and biodiversity.
• Climate change will continue to have significant effects on these resources over the next few decades and beyond.
• Climate change impacts on ecosystems will affect the services that ecosystems provide, such as cleaning water and removing carbon from the atmosphere.
• The complex interactions between change agents such as climate, land use alteration, and species invasion create dynamics that confound simple causal relationships and will severely complicate the development and assessment of mitigation and adaptation strategies.
• Existing monitoring systems, while useful for many purposes, are not optimized for detecting the impacts of climate change on ecosystems. As a result, it is likely that only the largest and most visible consequences of climate change are being detected. 

Some findings specific to agriculture:

• Grain and oilseed crops will mature more rapidly, but increasing temperatures will increase the risk of crop failures, particularly if precipitation decreases or becomes more variable.
• Horticultural crops (such as tomato, onion, and fruit) are more sensitive to climate change than grains and oilseed crops.
• Higher temperatures will negatively affect livestock. Warmer winters will reduce mortality but this will be more than offset by greater mortality in hotter summers. Hotter temperatures will also result in reduced productivity of livestock and dairy animals.
• Weeds grow more rapidly under elevated atmospheric CO2. Weeds will migrate northward and are less sensitive to herbicide applications. 

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