Effects Of Global Warming on Agriculture

The earth’s climate has been relatively stable for thousands of years. We know intuitively that it is hot, humid, and rainy in the Amazon, and that corn grows well in the US Midwest. We know that at a particular altitude we should plant a crop during a certain week of the year because conditions for it are just right then. For most of our memory as humans, our climates have closely oscillated around predictable patterns, and this has allowed us to feed ourselves and flourish.

When a stable climate system is modified beyond its “tipping point,” it gets out of balance and loses its equilibrium. While the system searches for a new set of patterns to stabilize around, variability and uncertainly are the norm. This, in essence, is the nature of the challenge that we are now facing.

Agriculture is one of the most weather-dependent of all human activities. It is ironic, then, that a significant percentage of greenhouse gas emissions come from agriculture. Fossil fuel-intensive agriculture is contributing to the creation of the unpredictable weather conditions that all farmers will need to battle in the not-too-distant future.

The Green Revolution of the 1960s and 1970s allowed us to increase yields by “borrowing” solar energy from the past in the form of fossil-fuel-based fertilizers and pesticides. When one adds in the oil used for processing and packaging foods and for refrigerating and shipping them long distances, it’s easy to see how the food industry consumes about 20% of all the oil used in the US.

About 1% of the world’s annual energy usage goes into the production of fertilizers. This might not seem like much, but it ties the price of food to that of natural gas, and will make food prices shoot up once energy supplies start to dwindle.

In the UK, food production and distribution account for 18% of greenhouse gas emissions. The 18% is split fairly evenly between “on-the-farm emissions” (from farming activities) and “beyond-the-farm emissions” (from transportation and processing activities, etc.).

While we’ve all gotten used to carbon dioxide being the bad boy on the global warming block, agriculture’s greenhouse-gas contributions include healthy shares of methane and nitrous oxide, both of which are more potent than CO2.

Finally, while production and transport of chemical fertilizers and pesticides lead directly to creation of greenhouse gases, use of these chemicals also does so indirectly by reducing farm soil’s capacity to store carbon.

So, what to do? Go organic! United Kingdom’s Environment Secretary notes that, in many cases, organic agriculture produces fewer greenhouse gases than conventional equivalents. There’s a catch, though. Organic food transported long distances is NOT helpful. So, go organic AND local.

We are already seeing some climate changes that may be indicative of what’s to come for agriculture:

1) Maple syrup production in the American northeast is suffering. The climate in which maple trees thrive is expected to move about two degrees (of latitude) north to Canada. Maple syrup production is already down by about 10% because of warmer and shorter winters.

2) The southwestern United States is already experiencing a lack of water – without water for irrigation, this area is too dry for large-scale agriculture – and serious desertification is expected to happen within the next few decades. Conditions similar to the Dust Bowl of the 1930s are expected to be the norm in the area by the 2030s.

3) All over the country, we are seeing earlier bird migrations and northward shifts in the ranges of crops and pests.

4) We’re also seeing increased peaks in spring run-off from glacier melt and snow-fed rivers.

Global-warming-related changes will affect the future of farming in myriad ways. Here are some examples:

1) The snow pack in California’s Sierra Mountains has been gradually declining for the last 50 years, and the latest Intergovernmental Panel on Climate Change (IPCC) report says that it could ultimately be reduced by 60% to 90%. This will result in a very serious lack of water for Central Valley farmers during the summer months. Southern California will be particularly hard hit.

2) A Colorado State University study shows that warming will cause Colorado’s grazing lands to become less productive.

3) Florida is expected to get heavier rains and flooding, which will be hard on citrus and other crops.

4) Most importantly for the US economy and for the “mainstream” industrial food system, which is primarily “corn-fed,” the latest climate models predict that it might become too hot and dry to grow corn in what is now called the Corn Belt.

Scientists believe that higher carbon dioxide levels and temperatures may actually increase yields slightly – as long as the temperature increase is no more that a few degrees C. Beyond that, the warming effect dominates and crop yields decrease. Keeping in mind that, so far, observed global warming effects keep surpassing scientists expectations (in a bad way), it seems likely that rising temperatures in farming regions will wreak havoc on crop yields.

Less availability of irrigation water due to warmer temperatures will also be a big negative for dry areas. Many of our most productive farming areas depend heavily on irrigation. Further, there is a local cooling effect in irrigated areas (from evaporating water) that moderates temperatures, helping crops survive withering summer temps. Thus, less irrigation will exacerbate global-warming-driven temperature increases in water-short areas. And remember – 40% of the world’s food supply comes from the 2% of land that is dependent on irrigation.

On the other side of the water issue, global warming is expected to increase “severe weather events.” That will be another blow to global agricultural output.

Globally, yields for many of the world’s main staple crops are bound to decline. A study by researchers at the Lawrence picture of parched corn Livermore National Labs and Stanford University compared yields for the world’s six main staple crops – wheat, rice, corn, soybeans, barley and sorghum – and found a 3% to 5% decline for every one degree of temperature increase. Those six crops account for at least 55% of non-meat calories consumed by people, and more than 70% of the world’s animal feed. The IPCC’s latest report estimates an average warming of between 3 and 11 degrees by the end of the century.

James Nash is a climate scientist with Greatest Planet (www.greatestplanet.org). Greatest Planet is a non-profit environmental organization specialising in carbon offset investments.

James Nash is solely responsible for the contents of this article.

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