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  A Publication of UVM Extension's Vermont Vegetable and Berry Program

Climate Change and Vermont Agriculture

by Vern Grubinger
Vegetable and Berry Specialist
University of Vermont Extension

Seems like the weather’s been extreme in recent years; heat waves, ice storms, floods, etc. How is this related to climate change? The answer is: indirectly. Weather events are not a good tool for assessing the climate, since climate is made up of weather patterns over many decades. There are ups and downs within seasons, but the trends over time are what counts. They include both temperature and precipitation patterns, and these affect environmental conditions, which in turn affect plants, animals and ecosystems.

Research conducted by the University of New Hampshire makes it pretty clear that the climate in our region is changing. Scientists analyzed data collected by hundreds of weather stations and found that the Northeast’s average annual temperature increased by 1.8 degrees F. from 1899-2000. Winters in particular have gotten warmer, with the average temperature from December through February warming by 2.8 degrees. It may not sound like a lot, but these changes have had significant effects on the environment, and therefore on farming.

For example, the Northeast frost-free growing season is 8 days longer than it was 100 years ago; the number of extreme precipitation events (more than 2 inches of rain in 48 hours) has increased from about 3 to 5 per year; there were, on average, 16 fewer days with snow on ground in 2001 than in 1970; apple and grape bloom dates were about two days earlier per decade from 1965 through 2001; and the maple sugaring begins 8 days earlier and ends 11 days earlier than it did 40 years ago.

Climate changes have been documented not just here but all over the globe, which means that farmers everywhere will be affected. The U.N. Intergovernmental Panel on Climate Change concluded in 2007 that the increased frequency of heat waves, droughts and floods will negatively affect crop yields and livestock, especially for subsistence farmers at low latitudes.

In places like Bangladesh, rising sea level is the climate change effect that outweighs all others in importance, since it is a low-lying country. In Vermont, climate change impacts are diverse, and they will have some positive as well as negative effects on farming. For example, a longer growing season can help the production of annual crops. In recent years we’ve seen mild autumns that allowed pumpkin and squash growers get higher yields, and let fall raspberry growers harvest fruit that would otherwise be lost to earlier frost.

But there are serious downsides to our changing climate, too. For example, studies suggest that two very important crops in Vermont– apples and maple syrup – may be negatively affected. Warmer winters could reduce apple fruit yields, and sugar maples in our area are likely to decline in health as the climate warms. The dairy industry will also face challenges, especially from an increase in summer temperatures since milk production drops off when cows are exposed to hot, humid weather.

Farmers will be able to cope with some climate changes more easily than to others, and this will depend on what they produce, where they’re located, and the extent of the change. (For a series of fact sheets about climate change impacts on agriculture in the Northeast, see: www.climateandfarming.org/clr-cc.php.) For example, it’s likely that cool season crops won’t do as well in areas that warm up significantly, but farmers who grow potatoes or crucifers can fairly easily switch to varieties that are more heat-tolerant, or change the types of annual crops they grow. Maintaining the comfort of heat-sensitive livestock such as dairy cows is also feasible with practices such as improved barn design to promote ventilation, or misting systems to provide evaporative cooling. Other problems will be harder to cope with, such as the gradual decline of perennial crop species, or the greater aggressiveness of weeds.

Rising CO2 levels may promote photosynthesis and thus the growth of crops, but the weeds in those crops may grow even better. Some fast-growing weeds are especially well adapted to utilizing extra CO2 because their photosynthetic system differs from most crops. Certain perennial weeds such as thistles and quackgrass that can store extra energy underground may become harder to control. Integrated weed management systems that combine tactics such as crop rotation, cover crops, cultivation, no-till production and mulching will become more important in the future.

Climate change will also alter pest populations, though exactly how is not clear. It‘s likely that new pests will arrive and some existing pests will become more abundant while others decline. For example, insect pests of crops that travel here on storm fronts from southern areas, such as leafhoppers, corn earworm and armyworms could become more abundant as summer storm frequency increases. Other pests that overwinter here, such as the European corn borer, flea beetle and tarnished plant bug could become more abundant if milder winters encourage their survival, although reduced snow cover might lower overwintering populations. Changes in rainfall patterns will affect crop diseases, since most of them require moisture to proliferate. The likelihood of changes in pest pressure, plus the uncertainty about it, will make frequent monitoring for pests an even more important activity on farms than it already is now. Farmers will want to avoid being taken by surprise.

Greater variability in precipitation patterns will have a big impact on agriculture. Farmers will need to take steps to deal with more intense rainfall events in order to avoid soil erosion. This could include putting in drainage systems or establishing strips of permanent sod in or around fields. Dealing with longer periods of drought will call for more investment in irrigation and water storage.

Besides planning to adapt to climate change, farmers can also help mitigate the problem by reducing their greenhouse gas (GHG) emissions. Although agriculture generates only a small part of the nation’s GHG output—about 6% of the 2009 total—Vermont farmers, like everyone else, should do what they can to address the problem. The good news is that many agricultural actions that reduce GHG emissions can also enhance farm profitability. For example, renewable energy systems can reduce fossil fuel use and CO2 emissions while lowering energy costs.

In order to understand how farmers can help mitigate climate change, one needs to understand something about the greenhouse gases involved. While much of the focus on GHG reduction is on CO2, nitrous oxide (N20) and methane (CH4) are other gases that contribute to climate change. Although they are generated in smaller amounts by human activity than C02, they are far more potent in terms of their warming effect. However, compared to most other industries, agriculture produces proportionally more N2O and CH4 than carbon dioxide. (In general, methane from agriculture is released by livestock and manure, and nitrous oxide is released when excess nitrogen fertilizer is applied under certain soil conditions.)

Given the information above, there are a several key steps that farmers can take to reduce GHG emissions, including:

  • Using nitrogen fertilizer more efficiently in order to avoid N2O emissions. This involves proper timing, placement and application rates.
  • Taking CO2 from the atmosphere and sequestering (storing) it in plant biomass and soils. This can be done through increased use of cover crops, permanent pastures and reduced tillage systems that ‘tie up’ atmospheric carbon while building soil organic matter.
  • Increasing the efficiency of farm inputs such as fuel, fertilizers, and pesticides, thus reducing consumption of fossil energy that is required to produce them.
  • Increasing production of biological-based energy to replace fossil energy. Vermont farms already offer many examples of this, from anaerobic digesters that make electricity from dairy manure, to on-farm biodiesel production using oil from canola and sunflower crops.
  • Switching to non-carbon energy sources such as wind and solar; and using energy efficient equipment for heating, cooling and tillage;

With the support of consumers, Vermont farmers can also use the marketplace to combat climate change. Growing the demand for local food products can improve the efficiency of food distribution and thereby reduce the energy consumed by storage and transportation. Eating fresh foods purchased from local farms can also avoid the need for packaging and refrigeration, further reducing fossil fuel use and GHG emissions. Of course, this assumes that local food is aggregated at roadside stands, farmers’ markets, food coops, cafeterias and the like. Driving from place to place to purchase small quantities of local food is not efficient.

Although the effects of climate change are daunting and somewhat uncertain, it makes sense to take steps to protect our agricultural landscape for generations to come. These steps include planning ahead to prepare for likely changes while working to reduce greenhouse gas emissions. Many farmers are already taking the initiative in these areas with innovative on-farm practices. Consumers can take action by continuing to buy local food, adding climate change to the list of reasons for doing so.


Published/last revised: May 2011
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