6.2—New herbicide-tolerant crops help the environment, reduce agricultural impacts

New herbicide-tolerant crops promote environmentally beneficial no-till farming and have shifted herbicide use to more-ideal chemicals.

See Genetic Roulette’s False Claims at Bottom of Page

Analysis of Peer-Reviewed Research:

The safety of herbicides has little to do with the safety of genetic engineering, and many herbicide tolerant crops – e.g. atrazine and imidazolidone tolerant crops- were not developed using genetic engineering.  Atrazine herbicide tolerant non-GM canola for instance, has been widely used even though atrazine herbicide is banned in some countries.  Herbicide safety is a farm management safety issue, not a genetic technology issue. Conventional crops that are herbicide-tolerant pose similar safety issues to those raised by GM crops.

Globally, no major increases in total amount of herbicide use can be attributed to genetically engineered crops. In some crops (cotton and canola) GM technology has led to significantly decreased (13 percent) usage of herbicide, measured as active ingredient applied per hectare.  More importantly, transgenic crops have allowed a shift to herbicides that have lower environmental impact, and GM crops have given 14  percent reduction in environmental impact world-wide (Brooks G, Barfoot P 2007). In the USA, US government reports show corn herbicide applications trending down from 1995 through 2002, as were cotton herbicide applications 1995 through 2001 (Fernandez-Cornejo and Caswell  2006). Genetic Roulette is out of date and incomplete on herbicide use statistics, and has missed these trends.

The main new use of herbicide made possible with transgenic crops, post-crop emergence spraying with glyphosate, the active component of Roundup Ready herbicide to control weeds, is very safe as glyphosate is non-toxic to humans and does not easily leach into streams and rivers. Glyphosate tolerant crops many provide safety and environmental benefits that Genetic Roulette doesn’t acknowledge. They have helped the widespread adoption of no-tillage farming in North and South America, saving soil, water, diesel fuel, herbicide run-off, and carbon emissions.  Reduced use of other herbicides than glyphosate, for instance,  imazethapyr, chlorimuron, pendimethalin, and trifluralin on soybeans (CASTS 2004), made possible by transgenic glyphasate tolerant soybean varieties, reduces potential health hazards from herbicide contamination.

1. Herbicides vary in their potential environmental and health impacts. Not all herbicides are the same. In terms of potential health effects, it is not just the amount of herbicide chemical residues present in soil or on crops, but what effect that herbicide has on living systems. This biological effect can be given a scientific ranking,  for instance by assessing different herbicides with an environmental impact quotient EIQ . A low EIQ means a safer herbicide (Brooks G and Barfoot P 2006; Brooks and Barfoot P 2007; Crossan and Kennnedy 2004; Devos and others  2008; Kovach and others 1992).

2.  Genetic engineering allows more choice in herbicides and the choice provides more safety. Herbicides are an important part of productive and sustainable farming. They can improve food output, reduce labour and fuel use, minimise soil loss and erosion, reduce leaching into water systems, and increase carbon build-up in the soil by helping the introduction of no-till farming and other environmentally friendly conservation tillage practices (Fernandez-Cornejo , Caswell  2006, Devos Y  and others 2008). Conventional crops often restrict the range of herbicides that can be used by farmers, and the available choice will often only be herbicides with higher EIQs.

3.  Biotechnology has not increased health risks from herbicide residues in food. Glyphosate is arguably the least toxic herbicide known. It has a very low EIQ. It rapidly converted to non-active breakdown products by microbes making it non-persistent. One of the glyphosate breakdown products, AMPA, is mentioned by Smith. He does not mention though, that AMPA is present in no more than trace quantities in foods and that it is considered to be of no toxicological concern (OECD  1999).  Neither glyphosate nor its degradation product AMPA  is absorbed from the gut. They do not bioaccumulate in any body tissue, and both have been extensively tested in rodent feeding trials for safeness (Williams and others 2000). As is often the case in Genetic Roulette, this safety testing is not mentioned even though it is provided in papers cited by Smith. He has done a very poor job at informing the reader about what is known about glyphosate and AMPA safety.

As the glyphosate used with greatly expanded acreages of transgenic crops has displaced other herbicides such as imazethapyr, chlorimuron, pendimethalin, and trifluralin herbicides from agriculture, decreasing their total usage by farmers, there is less chance of these other herbicides being present even in trace quantities in food. Genetic Roulette does not back up its claims that transgenic crops have increased herbicide contamination of food with any evidence about specific measurements of herbicide. They are just speculations that are almost certainly wrong.

4. Glyphosate-tolerant crops minimize herbicide run off into water systems. Glyphosate herbicide has several advantages as far as risks of chemical contamination in the water supply are concerned. It is strongly absorbed on to soil and so does not move with soil water. It’s rapidly metabolized to innocuous by products by soil microbes and so is not persistent in ecosystems. On top of its low toxicity, this means that aquatics ecosystems are less threatened by glyphosate use in agriculture than by use of other herbicides (Crossan and Kennedy 2004, CAST 2002). Similar safety for water ecosystems is provided by glufosinate-tolerance – the other major transgenic herbicide trait (Devos  and others  2008). Genetic Roulette does not discuss these environmental advantages of glyphosate and glufosinate even though they are very well documented.

5. Herbicide tolerant soybeans do not have altered phytoestogen levels.  Smith claims that herbicide tolerant soybeans have lower isoflavone levels than comparable conventional soybeans, quoting a group involved favouring herbal remedies for diseases. Oddly, he doesn’t notice that another paper he sites (Duke and others 2003) in a high-quality scientific journal, says there are no differences between transgenic and non-transgenic varieties, and this latter papers sites further studies that come to the same conclusion (Taylor and others 1999). There is an explanation for this difference between Smith’s opinions and the scientific literature — environmental conditions can cause isoflavones to go up or down dramatically. Smith has not been careful enough about taking into account the full range of conditions that can affect on food composition. He simply ignores evidence in papers he cites that contradicts his assertions.

References

Brooks G, Barfoot P (2006). Global impact of biotech crops: Socio-economic and environmental effects in the first ten years of commercial use. AgBioForum, 9(3): 139-151.

Brookes G, Barfoot P (2007). Global impact of biotech crops: Socio-economic and environmental effects, 1996-2006. AgBioForum, 11: 21-38. Available on the World Wide Web: www.agbioforum.org/

CAST (2002). Comparative Environmental Impacts of Biotechnology-derived and Traditional Soybean, Corn, and Cotton Crops.

Council for Agricultural Science and Technology, Carpenter, J., A. Felsot, T. Goode, M. Hammig, D. Onstad, and S. Sankula.

Ames, Iowa. www.cast-science.org. Sponsored by the United Soybean Board. www.unitedsoybean.org. Thus, soil behavioral characteristics of glyphosate make it an environmentally favorable herbicide compared to the available conventional herbicide options in soybean. Water quality would be significantly improved with the use of glyphosate in glyphosate tolerant soybean because of its tight and rapid soil sorption, rapid degradation by microorganisms, and significantly lower half-life compared to competing soybean herbicides.

Crossan A and Kennedy I (2004). University of Sydney report: A Snapshot of Roundup Ready® Cotton in Australia – Are there environmental benefits from the rapid adoption of Roundup Ready cotton in Australia? www.seedquest.com/News/releases/2004/august/9487.htm accessed Jan 14 2009

Devos and others  (2008). Environmental impact of herbicide regimes used with genetically modified herbicide-resistant maize. Transgenic Res (2008) 17:1059–1077DOI 10.1007/s11248-008-9181-8 Results showed that the environmental impact of herbicide regimes solely relying on the active ingredients glyphosate (GLY) or glufosinate-ammonium(GLU) is lower than that of herbicide regimes applied in non-GMHR maize. Due to the lower potential of GLY and GLU to contaminate ground water and their lower acute toxicity to aquatic organisms, the POCER exceedence factor values for the environment were reduced approximately by a sixth when GLYor GLU is used alone.

Duke SO and others (2003). Isoflavone, glyphosate, and aminomethylphosphonic acid levels in seeds of glyphosate-treated, glyphosate-resistant soybean.  J. Agric. Food Chem., 2003, 51 (1), 340-344

Fernandez-Cornejo J, Caswell M (2006). The First Decade of Genetically Engineered Crops in the United States, USDA-ERS. Economic Information Bulletin Number 11.

Adoption of GE crops is associated with reduced pesticide use.

Kovach, J., Petzoldt, C., Degni, J., & Tette, J. (1992). A method to measure the environmental impact of pesticides. New York’s Food and Life Sciences Bulletin. Geneva, NY: NYS Agricultural Experiment Station, Cornell University. Available on the World Wide Web: hdl.handle.net/1813/5203 accessed Jan 15 2009.

Organisation for Economic Co-operation and Development (OECD). 1999. Consensus Document on General Information Concerning the Genes and Their Enzymes That Confer Tolerance to Glyphosate Herbicide. Series on Harmonization of Regulatory Oversight in Biotechnology, No. 10, OECD Environment Directorate, Paris. www.oecd.org/ehs/public.htm

Sandermann H (2006) Plant biotechnology: ecological case studies on herbicide resistance. Trends in Plant Science Vol.11 No.7 July 2006

Taylor, N. B., and others (1999). Compositional analysis of glyphosate-tolerant soybeans treated with glyphosate. J. Agric. Food Chem. 1999, 47, 4469-4473.Herbicide treated soybeans do not different  isoflavone content.

Fernandez-Cornejo J, Caswell M (2006). The First Decade of Genetically Engineered Crops in the United States, USDA-ERS. Economic Information Bulletin Number 11.

Adoption of GE crops is associated with reduced pesticide use.

Pesticide use rates (in terms of active ingredient) on corn and soybeans have declined since the introduction of GE corn and soybeans in 1996 (fig. 8). In addition, ERS research suggests that, controlling for other factors, pesticide use declined with adoption. There was an overall reduction in pesticide use associated with the increased adoption of GE crops (Bt and HT cotton, HT corn, and HT soybeans combined, using 1997/1998 data), resulting in a significant reduction in potential exposure to pesticides (Fernandez-Cornejo and McBride, 2002). Overall pesticide use on corn, soybeans, and cotton declined by about 2.5 million pounds, despite the slight increase in the amount of herbicides applied to soybeans. In addition, glyphosate used on HT crops is less than one-third as toxic to humans, and not as likely to persist in the environment as the herbicides it replaces (Fernandez-Cornejo and McBride, 2002).

Williams GM, Kroes R, Munro IC. (2000). Safety evaluation and risk assessment of the herbicide Roundup and its active ingredient, glyphosate, for human. Regul Toxicol Pharmacol 31:117–165.

“The oral absorption of glyphosate and AMPA is low, and both materials are eliminated essentially unmetabolized. Dermal penetration studies with Roundup showed very low absorption. Experimental evidence has shown that neither glyphosate nor AMPA bioaccumulates in any animal tissue. No significant toxicity occurred in acute, subchronic, and chronic studies.”