Sometimes people wonder whether climate change really matters. They may ask, “What difference can a few degrees make?” or even complain, “We could use some of that global warming now” in the winter. Statistical predictions about changes in temperature and precipitation can seem abstract and unimportant to the average person watching the evening news, especially when other issues, such as the economy and national security are so pressing. However, it is important to remember that the increase in global average temperatures is only the tip of the melting iceberg, so to speak.

Altering the climate impacts the entire ecosystem, including agricultural crops that feed the world. The impact of climate change on the food supply brings the point home and shows why we should all care about the state of our climate.

Why crops are sensitive to climate change

In order to thrive, crops grown for food (such as rice, potatoes, corn, wheat, and soybeans) require specific ranges of temperatures and amounts of precipitation that follow a fairly regular pattern each season. Climate change alters temperature and the amount and timing of precipitation, which affects crops and the balance between beneficial and pest species that determine the health of the plants. Climate change may also damage crops through more frequent extreme weather events, such as heat waves, floods, droughts and hail.

Impacts on food supply so far

According to an article in the New York Times, consumption of the staples that supply most human calories (wheat, rice, corn and soybeans) has outstripped production for much of the past decade. The decline in production in many cases resulted from harvest failure due to natural disasters that scientists believe were to some extent either caused or worsened by global warming. These natural disasters included flooding in the U.S., heat waves in Europe and Russia and drought in Australia.

The most recent heat wave in the U.S. caused crop failure to push the price of corn to an all-time high in June ($7.80 per bushel compared to the average of $4.20).  The heat also kills livestock - as many as 4,000 cattle in Illinois died during the heat wave this summer.

Since 2007, food riots have broken out in more than 30 countries after two instances of massive spikes in international grain prices. High grain prices have a devastating effect on poorer countries, worsening hunger and political destabilization, and are thought to have played a role in the Arab uprisings in recent months.  

Predictions for the future   

Predictions for the future impact of a changing climate on agriculture vary considerably from region to region. Unfortunately, projections show that the parts of the world least able to adjust to declining food supplies will likely be the hardest hit. Developing countries are mainly located in the lower latitudes, closer to the equator, where temperatures are already high enough that further warming will easily pass the temperature threshold that leads to less healthy crops. The optimum latitude for crop growth will move towards the North Pole in the northern hemisphere and the South Pole in the southern hemisphere as temperatures increase.

One uncertainty in predicting future crop yields is the effect of carbon fertilization. Some plants grow faster in an environment richer in carbon dioxide, while others do not. Generally, plants that are considered invasive or pest species grow better in carbon dioxide rich conditions than desirables crops. Furthermore, the potential benefits of carbon fertilization are seemingly outweighed by the destructive weather patterns caused by global warming. The Peterson Institute for International Economics predicts that without the benefit of carbon fertilization, losses in agricultural productivity would be approximately 24% for Latin America, 28% for Africa and 30 to 40% for India. Developing countries such as these are harder hit by harvest failures, since agriculture makes up a greater part of their GDP than in developed countries, and they have less access to technology that can prevent flooding or minimize the impact of droughts.

Predictions for the U.S. are less dire. Without carbon fertilization, a 6% loss in agricultural productivity is predicted, but in the best case scenario where carbon fertilization works ideally, an aggregate gain of 8% is predicted.

Most of the attention of computer modeling studies is focused on grain crops, since they provide the majority of calories for the population worldwide. However, horticultural crops, such as tomatoes, onions and fruit, are likely at more risk from climate change than grain crops. Livestock are also sensitive to the changing climate, because of increases in disease, reductions in feed and forage crops, and extreme weather events.

Adapting to a new climate  

It is important to note that while the climate affects agriculture, the reverse is also true: agriculture affects the climate. Agricultural practices produce and release greenhouse gases (including CO2, methane, and nitrous oxide). Agriculture is responsible for 13.5% of global greenhouse gas emissions and 8.6% of greenhouse gas emissions in the United States, where a whopping 80% of nitrous oxide emissions and 30% of methane come from agriculture.   

Agriculture also contributes to global warming by causing changes in land cover. Converting rainforest land for agricultural purposes is an especially environmentally unfriendly practice, since it increases CO2 through deforestation. The amount of energy the earth absorbs from solar radiation depends on the reflectivity of the surface, which varies between land and water and even by the type of vegetation.  In many instances, land use changes from planting crops will increase the amount of heat the earth absorbs. However, researchers at the University of Bristol are investigating the potential of 'climate friendly crops' that would reflect more sunlight back out to space than the average variety currently planted.

Since climate change is already occurring and we continue to emit carbon dioxide at a steady rate, counting on climate change mitigation alone will not realistically address the problems of agricultural loss; adaptation strategies are also necessary. David Pimentel, professor of insect ecology at the College of Agriculture and Life Sciences at Cornell University in Ithaca, New York, suggests several strategies to help farmers adapt to agricultural changes caused by global warming:

• Soil and water conservation practices
• Improving Crop Varieties
• Crop Rotations
• Improved Pest Control
• Increasing soil organic matter
• Effectively using livestock wastes
• Increasing crop diversity
• Ridge-planting and developing wind breaks
• Irrigation (this option is more costly due to high energy use)
• Changing planting dates

Written by :

Elizabeth Klusinske