The Impact of Climate Change on Agriculture

Britt Lundgren's profileAt first I was excited to escape the inferno of August in Washington D.C. for a vacation in Maine, but after three straight days of rain I started to feel a certain amount of self-pity. On the fourth rainy morning, however, a visit to a farmer I used to work for quickly put my woes in perspective. The rain put a minor dent in my vacation, but it put a major dent in the growing season for Maine’s farmers.

Maine, New Hampshire, and Vermont all have received exceptional amounts of rain this summer, seriously damaging certain crops. Maine’s raspberry and green bean crops were devastated, and livestock feed crops (grain and hay) could not be harvested due to the wet weather. Many farmers will be paying high prices to truck in feed to replace what was lost.

No particular weather event can be reliably ascribed to climate change. But as I talked to my farmer friend, I began to wonder if this summer’s wet weather was a glimpse into the future for farmers in the region.

The IPCC predicts that regions that are already fairly wet will get even wetter over the next century. In the Northeastern U.S., precipitation is expected to increase by up to 5 percent in warmer months, and 10 percent in cooler months.

Precipitation in Maine this July was 25 percent above average, so even with the expected increase in precipitation most summers won’t be quite as bad for farmers (and vacationers!) as this one. Still, the consequences of increased precipitation in the future may look quite similar to what Northeast farmers are experiencing now:

  • Increased incidence of leaf and root pathogens is one of the worst problems with increased rainfall. Spread through the mold and fungus that thrive in the wet weather, these pathogens have had caused major damage to crops in Maine this summer. Wetter weather in the future is likely to cause similar problems.
  • New weeds migrating northward with warmer weather are another problem Northeast farmers can expect to encounter, according to the U.S. Climate Change Science Program report.
  • Traditional ways to control weeds won’t work as well. The report goes on to say "recent research suggests that glyphosate, the most widely used herbicide in the United States, loses its efficacy on weeds grown at the increased CO2 levels likely in the coming decades."

Net Plus or Net Minus?

Experts disagree on whether the overall impact of climate change on agriculture will be positive or negative. The impacts will vary from one region to the next. Higher levels of CO2 and higher temperature may lead to increased plant growth and longer growing seasons in some areas. But even this may not be all good. Several studies have found that high levels of CO2 can make food crops less nutritious.

Climate Change Impact on Agriculture in 2080
Map created by Hugo Ahlenius, UNEP/GRID-Arendal.

Changes in precipitation patterns and the spread of new weeds, insects, and pathogens could severely reduce yields. The Northeast is likely to experience wetter weather, and I’ve mentioned the problems this can cause. Other regions of the country – areas that produce higher volumes of crops – may experience increased drought, or more frequent and extreme rainfall events.

The IPCC predicts that, overall, climate change will cause a 5 to 10 percent increase in aggregate yields from non-irrigated agriculture. However, the report from the U.S. Climate Change Science Program predicts that productivity increases will only be short term:

[O]ver the long term, many such systems are likely to experience overall decreases in productivity that could result in economic losses, diminished ecosystem services, and the need for new, and in many cases significant, changes to management regimes.

One thing seems clear: farmers across the U.S. and around the world will have to cope with more unpredictable and extreme weather as the Earth warms.

This post is by Britt Lundgren, an agricultural policy specialist at Environmental Defense Fund.

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