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Effects of Global Warming on Agriculture

Global warming effects on agriculture and farming are a growing problem--and vice versa.

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Effects of Global Warming on Agriculture—and Vice Versa

It's not exactly clear why the '50s beatnik crowd thought the phrase "that's a gas, man" was cool. But today and in the future, ever-increasing amounts of gas—carbon dioxide, methane, and all the other members of the greenhouse gas gang—are likely to make the planet anything but cool. The climate effects will be far reaching, from higher electricity costs to soaring prices for the Spam and mashed potatoes on your plate.

Today's article explores not only the coming effects of global warming on agriculture, but also the impact that farming and agriculture are having on global warming. That is, how much are agriculture and food operations contributing to global climate change? And how at-risk is our food-production system from the effects of global warming?

We're fortunate to have a great guest article on this subject from Guillermo Payet of LocalHarvest, a web site that helps people find farmers markets, CSAs, and other local food sources in their area.

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Climate Change and Farming
 by Guillermo Payet, LocalHarvest

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's Contribution to Global Climate Change

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.

— Grinning Planet


Agriculture—Bracing for Global Warming

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

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

  • 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.
  • A Colorado State University study shows that warming will cause Colorado's grazing lands to become less productive.
  • Florida is expected to get heavier rains and flooding, which will be hard on citrus and other crops.
  • 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.

— Grinning Planet

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.


It's Note Hopeless—We Haven't "Bought the Farm" Yet

The good news is that we can still do something about it. Supporting sustainable agriculture by buying from your local organic farms is a significant action to take. Many small farms are now developing highly productive farming systems with low environmental impact. These are the right kinds of farms for the future. We are likely to achieve better results by learning to collaborate with nature rather than using brute-force to bend it to our will, as is the norm with today's widespread industrial agriculture practices.

The type of food we eat is as important as how farmers grow our food. Eating "lower on the food chain"—getting less of our protein from meat and more from nuts, seeds, beans, legumes, grains, and vegetables—can make a huge difference in the energy consumption associated with our personal menus.

Regardless of what corporate marketeers tell us, we cannot "save the world by shopping." Global climate change will dictate that the over-consumption binge of the last 50 years will have to come to an end. Changes in our eating habits and food systems will be a part of much larger changes in our culture. Adapting to the coming changes and avoiding further harm will require us to abandon the principle of immediate gratification and once again learn the benefits of frugality, conservation of resources, and thinking and acting with future generations in mind.

Changing our diets to healthier, more sustainable foods is not as hard as you might think. As the author Michael Pollan says:

"Eat food. Not too much. Mostly plants."

Add to that:

"Buy local and organic whenever possible."

Doing so will help reduce agriculture's effect on global warming and contribute to an overall healthier environment and better future.

Guillermo Payet is the founder of LocalHarvest, which works to help small farms develop relationships with local consumers and other market channels. Discover the safer, tastier, more varied, and better quality foods available via the listings at  

~    ~    ~


Grinning Planet Wrap-Up

Before we leave this topic, here are a few more facts, observations, and predictions regarding the effects of global warming on agriculture.

Global warming effects on California agriculture will be devastating to the US, which has, up to now, been self-sufficient in food production largely because of the productivity of California's farm fields. Increasingly frequent heat waves may reduce California's long-term agricultural output. Due to a three-week heat wave in 2006, beef, dairy, and poultry losses amounted to $85 million in Fresno County alone. Thousands of cows in San Joaquin Valley dropped dead in the heat. The timing of plant blossoming and the availability of pollinating insect may get out of sync. Fruit trees may yield less because there will be fewer cool nights (which help trees recover between harvests). Improved water management may be able to mitigate the problem of reduced mountain snowpacks to some extent, but water-management technology costs money! Expect higher food prices as the region that produces nearly half of US fruit and vegetables comes under climate-change stress.

Half a world away, China—the world's most populous nation—faces its own climate-induced agricultural meltdown. Chinese scientists recently stated that global warming and climate change will increase the instability of China's food production, reducing output of wheat, corn and rice by as much as 37% in the latter half of the century. They also noted that evaporation rates for some inland rivers would increase by 15%, exacerbating China's already severe shortages of water for drinking and irrigation.

Fighting global climate change is not just a "green thing"; it's not just a cause célèbre born of Hollywood stars; it's a matter of survival. Learn what you can do on our Global Warming Solutions page.

Thanks again to LocalHarvest for today's guest article! If you want to find local food in your area—which we strongly recommend, both as one solution to global warming and as a hedge against peak oil—you can't beat the database at LocalHarvest.

Know someone who might like this article about the effects of global warming on agriculture?  Please forward it to them.

Grinning Planet publish date: 08-MAY-2007

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George Monbiot offers an ambitious program to avoid climate catastrophe—by cutting CO2 emissions by 90% by 2030. He supports his proposals with a rigorous investigation into what works, what doesn't, cost factors, and hurdles. He wages war on bad ideas as energetically as he promotes good ones. Monbiot's sense of urgency is genuine: "We are the last generation that can make this happen, and this is the last possible moment at which we can make it happen." (by George Monbiot)

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Where once scientists were concerned about gradual climate change, more and more now fear abrupt change resulting from the triggering of hidden tipping points. With Speed and Violence covers phenomena such as the melting permafrost in Siberia, the huge meltwater systems beneath the icecaps of Greenland and Antarctica, the thermohaline (ocean) conveyor system—and explains what such things portend for our future.


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