왜 유전자조작이 가뭄에 대한 해결책이 아닌가

미국의 가뭄과 농업.pdf

High and Dry is the third in a series of reports highlighting genetic engineering’s limitations and demonstrating the importance of increasing public investment in more effective—but often neglected—agricultural technologies. The first two reports in the series are Failure to Yield and No Sure Fix.

Droughts can be devastating to farmers and to the people who depend on the food those farmers produce. The historic Texas drought of 2011 caused a record $5.2 billion in agricultural losses, making it the most costly drought on record.

While extreme droughts capture the most attention, mild and moderate droughts are more common and collectively cause extensive damage. Climate scientists expect the frequency and severity of such droughts to increase as the global climate heats up.

Furthermore, agriculture accounts for the lion's share of water extracted from rivers and wells, setting up conflicts between food production and other uses. Other important organisms, such as fish, also compete with humans for fresh water. So there is a vital need for crop improvements that will increase drought tolerance and water use efficiency (WUE).

Biotechnology companies such as Monsanto have held out the promise that genetic engineering can accomplish these goals, creating new crop varieties that can thrive under drought conditions and reduce water demand even under normal conditions. High and Dryoffers an analysis of the prospects for delivering on that promise.

Extent and severity of drought conditions in the U.S. on August 30, 2011. The darker areas are regions of severe to exceptional drought where cspB corn would likely be of little use. (Click on map for larger version with legend.)

A Small Bang for Big Bucks

Though the mid-2000's saw a surge in field trials for crop varieties with engineered drought tolerance traits, as of 2012 only one such variety—Monsanto's DroughtGard, containing the engineered genecspB—had been approved by the USDA.

The results so far paint a less than spectacular picture of DroughtGard's effectiveness: USDA analysis of data supplied by Monsanto show that DroughtGard produces only modest results, and only under moderate drought conditions at that. The report estimates that cspB corn would increase the overall productivity of the U.S. corn crop by only about one percent. And DroughtGard does not improve water use efficiency.

The evidence suggests that alternatives to GE—classical breeding, improved farming practices, or crops naturally more drought-tolerant than corn, such as sorghum and millet—can produce better results, often at lower cost. If we neglect these alternatives because of exaggerated expectations about the benefits of GE, we risk leaving farmers and the public high and dry when it comes to ensuring that we will have enough food and clean freshwater to meet everyone's needs.

Why Drought Tolerance Is So Challenging

There are several reasons why a GE magic bullet for drought tolerance may prove elusive. Drought tolerance is a complex trait that can involve many different genes, corresponding to different ways the plant can respond to drought; genetic engineering can manipulate only a few genes at a time. And in the real world, droughts vary widely in severity and duration, affecting the crop at different stages of its growth, so any engineered gene will be more successful under some drought conditions than others.

Genes that improve drought tolerance may have other effects on crop growth, some of which may be undesirable—a phenomenon known as pleiotropy. This has been commonly observed with many otherwise promising drought tolerance genes, and is likely a reflection of the interconnectedness of drought response with many other aspects of plant growth.

Molecular biologists try to reduce the negative effects of pleiotropy by ensuring that the engineered genes only become active under drought conditions, but if droughts are prolonged, the harmful effects may be hard to avoid.

Market Uncertainties

If Monsanto's cspB corn can meet these challenges, it will still face market hurdles. For starters, DroughtGard will have to compete in the marketplace with drought-tolerant varieties produced through less expensive breeding methods.

Another challenge for cspB corn is that farmers buy their seeds well before they plant. Because drought is not reliably predictable, many farmers may not want to pay the higher price of engineered drought tolerance just in case drought occurs. This may largely restrict planting of cspB corn mainly to areas where moderate drought is frequent, such as the western regions of the U.S. Corn Belt.

Other factors important for marketing seed include the overall quality of the corn varieties that the cspB is placed in and how these compare to competitors varieties.

Recommendations

Given the status of R&D on GE drought tolerance and water use efficiency and challenging questions about its prospects, UCS recommends that:

• Congress and the USDA should substantially increase support for public crop-breeding programs to improve drought tolerance.
• Congress and the USDA should use conservation programs funded under the federal Farm Bill to expand the use of available methods for improving drought tolerance and WUE.
• The USDA and public universities should increase research devoted to finding better ways to store and conserve soil water, groundwater, and surface water, and better farming methods to withstand drought.
• In particular, organic and similar methods that improve soil fertility simultaneously improve the capacity of soil to store water for crop use during drought, while mulches can reduce soil temperature and reduce evaporation. These methods should be encouraged through incentives.   
• Public and private research institutions should devote more funding and effort to improve crops that are important in drought-prone regions in the Southern Hemisphere.
• Researchers at the USDA and public universities should carefully monitor the efficacy and possible undesirable effects of cspB corn. Such monitoring is important because this variety is the first GE commercial drought-tolerant crop, and the resulting information would enhance our understanding of GE drought tolerance.
• The USDA and public universities should expand their research on using plant breeding to improve water use efficiency—a vital concern that has not attracted major efforts from the biotechnology industry.

미국의 가뭄과 농업.pdf

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