The images about the potential consequences of global warming are stark.
- The flow of ice from melting glaciers in Greenland has more than doubled over the last decade.
- The number of severe hurricanes has almost doubled in the last 30 years.
- Global sea levels could rise by more than 20 feet with the loss of shelf ice in Greenland and Antarctica, flooding port cities and coastal farms worldwide.
- The Arctic Ocean could be devoid of ice by the summer of 2050 destroying the habitat of species like polar bears.
- Heat waves, droughts and wildfires could occur more often. Each catastrophe could be worse the earlier ones, threatening large agricultural areas especially in places like India, Africa and Latin America – where more of the world’s poor live.
In the last third of the 20th century, global warming trends have been increasingly documented and accepted in the scientific community. The weight of scientific evidence and opinion now says that our worldwide climate is changing because of manmade processes.
Global warming will have significant impacts on agriculture. On the one hand, the world’s food supplies could be threatened as global warming progresses. On the other hand, farmers could help reduce climate changes by changing their farming practices.
In fact, in February 2009, the Environmental Proection Agency (EPA) officially designated carbon dioxide (CO2) and five other heat trapping gases as pollutants dangerous to the environment. The Obama administration made the determination after the U.S. Supreme Court ordered the Bush administration to look at greenhouse gases. The Bush administration ignored the ruling. The determination is the first step in a process that will lead to the regulation of the gases for the first time in the United States, and that could have profound affects on transportation, manufacturing costs, agriculture and power generation.
We have more about the history of global warming research and what agriculture can do in the Water section of this Web site.
Crops threatened. There are some who might argue that rising levels of carbon dioxide will be good for agriculture – after all, plants use CO2 as a “food source,” combining it with water and light energy to produce carbohydrates and the oxygen that humans need to live. The problem comes when average temperatures rise enough to alter weather patterns, growing seasons and pressure from weeds, pests and diseases.
For instance, the International Maize and Wheat Improvement Center in Mexico – the center that Norman Borlaug worked at – recently concluded that wheat growers in North America will have to give up some of their southernmost fields in the next few decades as those areas get too hot for the crop. On other hand, new wheat fields in the north will make wheat growers of farmers from Canada to Russia.
Siberia will become a major notch in the wheat belt.
Continents without cooler climates to move into could lose huge sections of crop-growing regions to global warming. According to a summary of scientific studies in the Washington Post, India could see a 40 percent drop in agricultural productivity by 2080. Africa – where four out of five people make their living directly from the land – could drop 30 percent in food production. Countries like Senegal and war-torn Sudan could experience a complete agricultural collapse. Latin America could experience a 20 percent drop, overturning tremendous ag progress in countries like Brazil.
In the U.S., studies at Cornell University say that the average growing season in the Northeast has already expanded by an average of eight days. There has also been an increase in the frequency of extreme rain events.
Studies have shown that weeds can make use better of increased carbon dioxide than crops can, and higher CO2 could make herbicides less effective. Add to these factors to longer growing seasons, and northern agricultural breadbaskets could be invaded by southern weeds like kudzu.
Insect pests will probably become more of a problem, as well. Insects are cold-blooded organisms. According to the Cornell study, “temperature is probably the single most important environmental factor influencing insect behavior, distribution, development, survival and reproduction.” Another study found that just a 2° Celsius increase in average temperature could give insect pests up to five additional life cycles during a single crop growing season, greatly increasing the potential damage insects can do.
Livestock can also be threatened by global warming. Animals are directly affected by heat stress lowering milk production in dairy cattle and birthing and growth rates in feedlots, as well as poultry hatcheries, hog farrowing and cow-calf operations. Indirectly, the price of feed may increase.
Are farmers part of the problem? Agriculture does contribute to the global warming through several means –
- Farmers drive tractors and cars that release CO2 into the atmosphere.
- Methane is released from decomposing animal manure and rice cultivation.
- Nitrous Oxide is released when more fertilizer is applied to fields than the crops can utilize.
- Land use. Farmers contribute to global warming indirectly when they clear land of trees for more crops.
In all, some scientists estimate that agricultural practices worldwide account for around 12 percent of all greenhouse gas emissions. By comparison, transportation fuels account for 14 percent and power stations top the list with 21 percent of all emissions.
What farmers can do. Prescriptions for the future fall into two categories – changes that farmers could make to reduce their contributions to greenhouse gases, and changes that farmers will have to make to stay in business.
In many cases, the strategies for reducing greenhouse gas emissions actually amount to using the best farming practices available.
- Testing for soil nutrient levels and only applying as much nitrogen fertilizer as you need can reduce nitrous oxide emissions at the same time as it reduces the high cost of fertilizer.
- Conservation or no-till practices can reduce evaporation and the need for irrigation and can reduce the amount of carbon dioxide released from both the soil and the tractor. Burying crop residue traps the carbon in the plants below ground in a process called carbon sequestration.
- Ag scientist will need to quickly develop new crop varieties that can adapt to changes in growing seasons and rain patterns. Ancient crop varieties or genetically modified organisms (GMOs) may be needed to adapt to global warming. For instance, as sea levels rise, coastal croplands become saltier. Researchers have discovered ancient varieties of Persian grasses that can tolerate salt water. Scientists are breeding the grasses with commercial wheat and have found the hybrids are growing well in Australia’s increasingly salty soils. Other researchers are trying to develop GMO rice varieties can survive up to two weeks totally submerged.
- The production of biofuels, like ethanol, could help reduce greenhouse gases. There has been a lot of debate about the relative merits of ethanol or other biofuels, and we’ll explore that debate in detail in later stories.
In order to stay in business as the climate changes, farmers may have to significantly change their farming practices.
- Farmers may have to change their planting and harvest dates.
- They may have to change the varieties of crops that they crow to take advantage of longer growing seasons or drier climates or more rainy periods, all depending on the local conditions.
- They may have to increase their water use.
- They may have to use more chemicals to respond to increasing weed and pest pressure.
- They may have to go to entirely new crops and find new markets for those crops.
Dr. Don Lee (right) is one of the scientists who believes that global warming will have significant effects on farming. The plant geneticist from the University of Nebraska-Lincoln says, “If we see just a few degrees change in average temperatures that will make a huge influence on how well our plants grow. And so, we have to be prepared for that if we can’t tide that, or change the trend towards warmer temperatures throughout the globe. Some plants will do better. Some plants will do much worse.”
Farmers may not be buying all of the talk about global warming. A 2007 study from Cornell University’s extension service found that, “At present there is little call from farmers to address the issue. In fact, some farmers, just like some of the general public, are skeptical that climate change is even real. Others are doubtful it will affect agriculture, and some don’t even want to bring it up for fear it might generate yet another concern about the environmental impact of farming.”
But the study went on to assert, “The scientific evidence leaves little room for doubt that our climate is changing, and that agriculture will be affected.”
Written by Bill Ganzel, the Ganzel Group. First published in 2009. A partial bibliography of sources is here.