농약 사용에 관한 유전자조작 작물의 영향 (미국유기농센터의 연구결과)

유전자조작 옥수수, 콩, 면화 등 유전자조작(GM) 작물이 미국에 처음으로 상업적으로 도입된 1996년부터 2008년까지 13년 동안 농약사용에 어떤 영향을 미쳤는지에 대해 미 농무부(USDA) 자료를 근거로 실증적으로 분석한 연구결과입니다.

저자는 제초제 사용량이 엄청나게 늘어남에 따라 살충제 사용량이 줄어들었는데… 그 원인은 유전자조작 옥수수, 콩, 면화 등 유전자조작(GM) 작물때문이라고 분석하고 있습니다.

제초제 사용량의 증가는 제초제 내성 잡초의 출현을 불러왔습니다. 농업분야는 농약의 독성 공해 문제뿐만 아니라 기후변화와 세계인구 증가라는 2개의 도전에 직면해 있습니다.

유전자조작 산업(생명공학산업)은 이러한 문제를 해결할 수 있다고 광고하고 있습니다. 그들은 유전자조작 곡물이 농약사용량을 감소시킬 것이라고 약속한 바 있기도 합니다.

저자는 우리가 유전자조작 산업계의 이러한 광고와 약속을 문제의 해결책으로 수용하기 전에 이들의 처음 약속에 관한 기록들을 추적하여 냉정하게 데이터에 근거한 평가를 해봐야 한다고 주장합니다.

유전자조작(GM) 작물은 미국에 처음으로 상업적으로 도입된 1996년부터 2008년까지 13년 동안 3억1840만 파운드의 농약을  사용함으로써 제조체 내성 및 Bt 종자를 사용하지 않은 비유전자조작 작물과 비교해 볼 때  엄청나게 많은 농약을 사용했습니다.

Bt 옥수수와 면화는 지난 13년 동안 6420만 파운드의 살충제 사용을 감소시켰습니다. 그러나 제초제 내성 잡초들로 인해서 지난 13년 동안 3억 8260만 파운드의 제초제 사용량이 증가했습니다.

게다가 최근 GM 작물로 인한 제초제 사용량은 가파르게 상승하고 있습니다. 특히 옥수수, 콩, 면화 등 3가지 작물 경작에 사용된 제초제 사용량은 2007년과 2008년 경작년도에 48%나 증가했습니다. 제초제 내성 잡초들로 인한 제초제 사용량은 2007년과 2008년 경작년도에 31.4%나 증가했습니다.

유전자조작 작물은 상업적 도입 최초 3년간(1996~1998년)은 농약 사용량이 1996년 1.2%, 1997년 2.3%, 1998년  2.3%로 감소했습니다. 그러나 농약사용량은 2007년 20%, 2008년 27% 증가했습니다. 

이렇게 일반작물에 비해 유전자조작 작물의 농약사용량이 엄청나게 증가한 이유는 글리포세이트(glyphosate) 내성 잡초가 급격하게 많이 출현했기 때문입니다.

미국 농무부의 자료에 따르면,  유전자조작 작물이 재배되기 시작한 1996년 이후 글리포세이트(glyphosate) 사용량이 면화농장에서 3배씩, 콩농장에서 2배씩, 옥수수농장에서 39%씩 증가했습니다.(글리포세이트는  국내에서도 근사미,근자비,라운드업,글라신골드 성보글라신 등 다양한 명칭으로 상품화되어 판매되고 있으며, 몬산토에서 생산하는 대표적 농약이기도 합니다)

해마다 글리포세이트 사용량은 평균적으로 면화에서 18.2%, 콩에서 9.8%, 그리고 옥수수에서 4.3%씩 증가했습니다.

이러한 상태에서는 유전자조작 작물을 재배하는 미국의 농가의 입장에서도 경제적 이윤을 내기 힘들 것이라고 합니다. 왜냐하면 몬산토, 카길, 다우, 신젠타 등 유전자조작 기업은 유전자조작 종자를 로열티를 붙인 비싼 가격으로 판매하고 있으며, GM 종자와 패키지로 농약까지 판매하고 있기 때문에 수지타산을 맞추기가 어렵다는 분석입니다.

유전자조작 기업들은 비싼 특허종자를 판매하는 명분으로 농약사용량을 줄여서 재배농가가 더 많은 경제적 이윤을 획득하게 될 것이라고 홍보했었는데… 결국 이러한 홍보가 사실이 아니었다는 연구결과가 나왔다고 해석해야 할 것 같습니다.

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Impacts of Genetically Engineered Crops on Pesticide Use: The First Thirteen Years
November 2009
by Charles Benbrook

Accessing the report
The full report – pdf (3.68 MBs, 69 pages)
Executive Summary – pdf (1.44 MBs, 15 pages)
Supplemental Tables – pdf

Extracts collected and summarized by GMWatch

출처 : http://www.gmwatch.org/component/content/article/11696-cherry-picking-new-report-on-gm-and-pesticides
 
On the report’s purpose

This report explores the impact of the adoption of GM corn, soybean, and cotton on pesticide use in the United States, drawing principally on data from the US Department of Agriculture. The most striking finding is that GM crops have been responsible for an increase of 383 million pounds of herbicide use in the U.S. over the first 13 years of commercial use of GM crops (1996-2008).
 
This dramatic increase in the volume of herbicides applied swamps the decrease in insecticide use attributable to GM corn and cotton, making the overall chemical footprint of today’s GM crops decidedly negative. The report identifies, and discusses in detail, the primary cause of the increase — the emergence of herbicide-resistant weeds.
 
The steep rise in the pounds of herbicides applied with respect to most GM crop acres is not news to farmers. Weed control is now widely acknowledged as a serious management problem within GM cropping systems. Farmers and weed scientists across the heartland and cotton belt are now struggling to devise affordable and eff ective strategies to deal with the resistant weeds emerging in the wake of herbicide-tolerant crops.
 
But skyrocketing herbicide use is news to the public at large, which still harbors the illusion, fed by misleading industry claims and advertising, that biotechnology crops are reducing pesticide use.
 
In addition to toxic pollution from pesticides, agriculture faces the twin challenges of climate change and burgeoning world populations. The biotechnology industry’s current advertising campaigns promise to solve those problems, just as the industry once promised to reduce the chemical footprint of agriculture. Before we embrace GM crops as solution to these new challenges, we need a sober, data-driven appraisal of its track record on earlier pledges.
 
While the USDA continued to collect farm-level data on pesticide applications during most of the 13 years covered in this report, the Department has been essentially silent on the impacts of GM crops on pesticide use for almost a decade. This is why this report by Dr. Charles Benbrook was commissioned.
 
On the impacts of GM crops on pesticide use
 
GM crops have increased overall pesticide use by 318.4 million pounds over the first 13 years of commercial use, compared to the amount of pesticide likely to have been applied in the absence of HT (herbicide tolerant) and Bt seeds.
 
Bt corn and cotton have delivered consistent reductions in insecticide use totaling 64.2 million pounds over the 13 years. HT crops have increased herbicide use by a total of 382.6 million pounds over 13 years. HT soybeans increased herbicide use by 351 pounds (about 0.55 pound per acre), accounting for 92% of the total increase in herbicide use across the three HT crops.
 
Recently herbicide use on GM acres has veered sharply upward. Crop years 2007 and 2008 accounted for 46% of the increase in herbicide use over 13 years across the three HT crops (corn, soy and cotton). Herbicide use on HT crops rose a remarkable 31.4% from 2007 to 2008.
 
GM crops reduced overall pesticide use in the first three years of commercial introduction (1996-1998) by 1.2%, 2.3%, and 2.3% per year, but increased pesticide use by 20% in 2007 and by 27% in 2008.
 
Two major factors are driving the trend toward an increase in the pounds of herbicides used to control weeds on an acre planted to HT seeds, in comparison to conventional seeds:
*The emergence and rapid spread of weeds resistant to glyphosate, and
*Reductions in the application of herbicides applied on non-GM crop acres.
 
USDA NASS data show that since 1996, the glyphosate rate of application per crop year has tripled on cotton farms, doubled in the case of soybeans, and risen 39% on corn. The average annual increase in the pounds of glyphosate applied to cotton,
soybeans, and corn has been 18.2%, 9.8%, and 4.3%, respectively, since HT crops were introduced.
 
HT crops account for the lion’s share of total GM trait acreage – 72% over the first 13 years of commercial use and around three-quarters in most years. HT soybeans account for almost one-half of all GM trait acres. This is why HT soybeans are so important in terms of the overall impact of GM crops on the pounds of pesticides applied.
 
On the impact of Bt crops on pesticide use
 
The methodologies used by USDA to project pesticide use on conventional and GM-crop acres require a number of assumptions and projections, which may not be true.
 
1. One assumption is that Bt crop growers apply no chemical insecticides for the pests targeted by these traits, including cotton rootworm. But University of Illinois entomologists have documented spotty performance of Bt corn for Corn Root Worm control, especially under high population pressure, and reported that some growers have applied soil insecticides on Bt corn acres. So this assumption overstates the benefits of Bt technology regarding reducing insecticides.
 
2. Another assumption is that Bt corn planted for European Corn Borer and Southwestern Corn Borer can be credited with displacement of all the pounds of organophosphate or synthetic pyrethroid insecticides that would be applied to corn without the Bt trait. This assumption would overstate the benefits of the Bt technology regarding reducing insecticides, since a portion of most of these insecticides are applied by farmers for the control of other insects, including the Corn Root Worm.
 
3. A third assumption is that some portion of the acres planted to Bt corn displace insecticides. But before the commercial availability of Bt corn seed, some farmers were not treating their fields with insecticides. Historically, only around 35% of corn acres have been treated each year with an insecticide for control of the European Corn Borer, Southwestern Corn Borer, Corn Root Worm, and other insect pests. So this assumption overstates the benefits of Bt technology regarding reducing insecticides.
 
4. A fourth assumption is that the Bt toxins manufactured within the cells of Bt crops do not count as insecticides “applied” on Bt-crop acres. Opinions differ among experts on whether it is appropriate to count Bt toxins manufactured inside GM plants as equivalent to a Bt liquid insecticide sprayed on the outside of the plant.
 
One factor to bear in mind when considering this question is that liquid sprays expose pest populations to short-lived selection pressure, thereby reducing the risk of resistance. Bt liquid sprays are applied only when and as needed, consistent with the core principles of integrated pest management (IPM).
 
Bt plants, however, produce the toxin continuously during the growing season, not just when needed, and in nearly all plant tissues, not just where the toxins are needed to control attacking insects. In a year with low pest pressure, farmers can decide not to spray insecticides on a corn field, but they cannot stop Bt hybrids from manufacturing Bt toxins in nearly all plant cells.
  
On glyphosate-resistant weeds
 
Glyphosate-resistant (GR) weeds were practically unknown before the introduction of RR crops in 1996. Today, nine or more GR weeds collectively infest millions of acres of U.S. cropland. Thousands of fields harbor two or more resistant weeds. The South is most heavily impacted, though resistant weeds are rapidly emerging in the Midwest, and as far north as Minnesota, Wisconsin, and Michigan. Farmers can respond to resistant weeds on acres planted to HT crops in five ways:
*Applying additional herbicide active ingredients,
*Increasing herbicide application rates,
*Making multiple applications of herbicides previously sprayed only once,
*Through greater reliance on tillage for weed control, and
*By manual weeding.
In the period covered by this report, the first three of the above five responses have been by far the most common, and each increases the pounds of herbicides applied on HT crop acres.
 
GR pigweed (Palmer amaranth) has spread dramatically across the South since the first resistant populations were confirmed in 2005, and already poses a major threat to U.S. cotton production. Some infestations are so severe that cotton farmers have been forced to abandon cropland, or resort to the preindustrial practice of “chopping cotton” (hoeing weeds by hand).
 
GR weeds are not only driving increases in the use of glyphosate, but also the increased use of more toxic herbicides, including paraquat and 2,4-D, one component of the Vietnam War defoliant, Agent Orange.
 
On how GR weed problems will impact health and the environment
 
Growing reliance on older, higher-risk herbicides for management of resistant weeds on HT crop acres is now inevitable in the foreseeable future and will markedly deepen the environmental and public health footprint of weed management on over 100 million acres of U.S. cropland. This footprint will both deepen and grow more diverse, encompassing heightened risk of birth defects and other reproductive problems, more severe impacts on aquatic ecosystems, and more frequent instances of herbicide-driven damage to nearby crops and plants.
 
On the road ahead for GM crops
 
Crop year 2009 will probably mark several tipping points for RR crops. The acres planted to HT soybeans fell 1% from the year before, and will likely fall by a few additional percentage points in 2010. Farmer demand for conventional soybeans is outstripping supply in several states, and universities and regional seed companies are working together to close the gap. Reasons given by farmers for turning away from the RR system include the cost and challenges inherent in dealing with GR weeds, the sharply increasing price of RR seeds, premium prices offered for non-GM soybeans, the poorer than expected and promised yield performance of RR 2 soybeans in 2009, and the ability of farmers to save and replant conventional seeds (a traditional practice made illegal with the purchase of HT/RR seeds).
 
In regions where farmers are combating resistant weeds, university experts are projecting increases of up to $80 per acre in costs associated with HT crops in 2010. This increase represents a remarkable 28% of soybean income per acre over operating costs.
 
The economic picture dramatically darkens for farmers combating resistant weeds under average soybean yields (36 bushels) and market prices ($6.50 per bushel). Such average conditions would generate about $234 in gross income per acre. The estimated $80 increase in 2010 costs per acre of HT soybeans would then account for one-third of gross income per acre, and total cash operating costs would exceed $200 per acre, leaving just $34 to cover land, labor, management, debt, and all other fixed costs. Such a scenario leaves little or no room for profit at the farm level.
 
Monsanto and Syngenta are now offering to pay farmers rebates on the order of $12 per acre to spray herbicides that work through a mode of action different from glyphosate. Monsanto’s program will even pay farmers to purchase herbicides sold by competitors, a sign of how seriously Monsanto now views the threat posed by resistance to its own product.
 
While corn, soybean, and cotton farmers view the spread of resistant weeds as a slow moving train wreck eroding their bottom line, the seed and pesticide industry sees new market opportunities and profit potential arising in the wake of resistant weeds. A large portion of industry R&D investments are going into the development of crops that will either withstand higher rates of glyphosate applications, or tolerate applications of additional herbicides, or both. In short, the industry’s response is more of the same.
 
One major biotech company has applied for and received a patent covering HT crops that can be directly sprayed with herbicide products falling within seven or more different chemical families.