全球变暖威胁美国和世界农业

Global Warming a Threat to United States and World Agriculture

Added by Chester Davis on April 1, 2014.

global warmingIn a review of scientific papers published since 2007 the Intergovernmental Panel on Climate Change declared that the world is already experiencing the impacts of climate change in areas like global security and food production. Global warming is a threat to agriculture in the United States and around the world, say the report’s authors.

These results were part of an extensive analysis and summary of climate change research published this week by the IPCC. Lead author Dr. Michael Oppenheimer said that food supply is the most pressing matter.

In North America, the IPCC reports several likely ways that food production will be disrupted. The report states with high confidence that climate change will have major impact on fisheries off both the East and West coasts of the United States.

Climate change will have a major impact on snow, rain and ice packs in the Rocky Mountains, and on potential rainfall in California. Both of those impacts are reported with high confidence that climate change will have a major impact in those areas. Climate change will affect rainfall in the Midwest, with moderate confidence.

The effects of climate change will be felt in key food-producing regions of the United States, the report stated. Apple orchards in Washington, cherry orchards in California, and wine-growing regions across the country could be negatively affected in coming decades.

Wine grapes are currently grown in several U.S. states, including California and Virginia. Portugal and British Columbia may become better wine-growing areas though.

Fish species that are a critical source of food for many, will move to escape warming waters. Catches in some parts of Antarctica and the tropics could decrease by 50 percent in coming decades. North American fisheries may also be hurt.

The new report highlights food security as an area of particular concern as crop yields for maize, rice and wheat are expected to decline in coming decades. About one in 10 projections show losses of over 25% for those crops.

Previous climate change studies have found mixed impacts on food production, with production increasing in some areas and other areas being hurt badly. The report authors state with high confidence that those negative impacts have been more common than the positive ones.

In 2007 the IPCC reported that it was too early to tell if climate change would increase or decrease food production, so there was still a possibility of the world becoming greener. In the past few years scientific research has shown that climate change hurts food production, according to Chris Field, of the Carnegie Institution of Science and the climate report’s lead author.

The report also explains that global warming is altering rainfall patterns, melting snow and ice, and negatively affecting water resources, with medium confidence. To the extent this is correct, climate change is a threat to agriculture in the United States and around the world.

After 2050, the risk of severe impacts on yields increases, along with boom-and-bust cycles in many regions. At the same time, global demand for food will grow as the population rises to an estimated nine billion.

According to the Summary for Policymakers, food prices are likely to rise from three percent to 84 percent by 2050 due only to climate change. That increase varies with the severity of climate change.

Some weather-related impacts of climate change are evident, the IPCC found. Hurricane Sandy, a 2011 storm that did over $20 billion in damage to the eastern United States, was not caused by climate change, but was made worse because sea level is about a foot higher than it was a century ago.

The projected impacts of climate change on food production could be mitigated in several ways, the report notes. More use of plants genetically engineered to resist drought, use of drought-tolerant crop varieties, and better irrigation methods could all be used to deal with unreliable water supplies.

That global warming threatens food production in the United States, and the world, in coming decades now seems certain unless dramatic adaptation efforts begin soon, according to the IPCC.

By Chester Davis