Truth: GM has had little impact on the adoption of no-till farming, and no-till with GM herbicide-tolerant crops is not environmentally friendly

Myth at a glance

GMO proponents claim that GM herbicide-tolerant crops, notably GM Roundup Ready (RR) crops, are environmentally friendly because they allow farmers to adopt the no-till system of cultivation. No-till farming avoids ploughing in order to conserve soil and water. It is claimed to reduce carbon dioxide emissions by sequestering more carbon in the soil.

In no-till cultivation of GM herbicide-tolerant crops, farmers try to control weeds through herbicide applications rather than mechanically, by ploughing.

However, USDA data show that the introduction of GM crops did not significantly increase no-till adoption.

A study comparing the environmental impact of GM RR and non-GM soy found that once the ecological damage caused by herbicides is taken into account, the negative environmental impact of GM soy is greater than that of non-GM soy in both no-till and tillage systems. Also, the adoption of no-till raised the negative environmental impact level, whether the soy was GM RR or non-GM.

No-till fields do not sequester more carbon than ploughed fields when carbon sequestration at soil depths greater than 30 cm is taken into account.

Claims of environmental benefits from no-till herbicide-tolerant farming systems are unjustified.

GMO proponents claim that GM herbicide-tolerant crops, notably GM Roundup Ready (RR) crops, are environmentally friendly because they allow farmers to adopt the no-till system of cultivation. No-till farming avoids ploughing in order to conserve soil and water. It is claimed to reduce carbon dioxide emissions by sequestering more carbon in the soil.

In no-till cultivation of GM herbicide-tolerant crops, farmers try to control weeds through herbicide applications rather than mechanically, by ploughing.

There are several problems with the inflated claims made for the environmental benefits of this farming system, which are detailed below.

GM is not needed to practise no-till

No-till or low-till farming can be – and is – practised in chemically-based non-GM and agroecological farming. Farmers do not have to adopt GM crops or use herbicides to practise no-till.

GM has not significantly increased the adoption of no-till

The vast majority of no-till and low-till adoption in the US occurred before GM crops came onto the market and rates of adoption have stagnated since, according to a US Department of Agriculture report. The report says that adoption of no-till and low-till for soybeans grew from 25% of the soybean acreage in 1990 to 48% in 1995, the 5-year period previous to the introduction of GM herbicide-tolerant soybeans. Growth of no-till and low-till increased further in 1996, the year herbicide-tolerant soybeans were introduced, but then stagnated to 50–60% in the following years.1

Biotechnology expert Dr Doug Gurian-Sherman of the Union of Concerned Scientists commented on the findings: “Roundup Ready crops have made no-till easier, but so have no-till seed drills, and Farm Bill incentives that went into effect in 1986. If you actually look at the additional adoption of no-till after 1996, it is only a few per cent in corn, almost nothing in cotton, and a little more in soy (maybe 5 to 10% of acres). So contrary to the widespread myth, the data do not support a major role of GM crops in the increase in no-till over the past few decades.”2

Claims of environmental benefits for no-till with GM are misleading

Claims of environmental benefits for GM herbicide-tolerant crops with no-till cultivation are misleading. One study compared the environmental impacts of growing GM RR and non-GM soy, using an indicator called Environmental Impact Quotient (EIQ). EIQ assesses the negative environmental impacts of the use of pesticides and herbicides on farm workers, consumers and ecology (fish, birds, bees and other beneficial insects).

The study found that in Argentina, the negative environmental impact of GM soy was higher than that of non-GM soy in both no-till and tillage systems, because of the herbicides used. These are broad-spectrum in nature – that is, they kill all plants except GM plants engineered to tolerate them. Also, the adoption of no-till raised the EIQ, whether the soy was GM RR or non-GM. The main reason for the increase in herbicides used in no-till systems was the spread of glyphosate-resistant superweeds.3

The spread of herbicide-resistant superweeds has undermined the GM no-till model of farming, forcing farmers back to ploughing and even pulling weeds by hand.4

No-till farming does not sequester more carbon

Chemically-based agriculture is a major contributor to climate change, producing over 20% of greenhouse gas emissions.5 GMO proponents claim that soil in no-till systems sequesters (stores) more carbon than ploughed soil, preventing the carbon from being released into the atmosphere as the greenhouse gas carbon dioxide and thus helping to mitigate climate change.

However, a comprehensive review of the scientific literature found that no-till fields sequester no more carbon than ploughed fields when carbon sequestration at soil depths greater than 30 cm is taken into account. Studies claiming to find carbon sequestration benefits from no-till only measure carbon sequestration down to a depth of about 30 cm and so do not give an accurate picture.6

Conclusion

Claims of environmental benefits from no-till farming with GM crops are misleading and unjustified. No-till farming can be and is practised by chemically-based non-GM and agroecological growers and it is not necessary to grow GM crops to practise it. The introduction of GM crops has not significantly increased no-till adoption.

No-till farming with GM herbicide-tolerant crops is not environmentally friendly. A study carried out in Argentina found that the negative environmental impact of GM soy was higher than that of non-GM soy in both no-till and tillage systems, because of the herbicides used. No-till fields also do not sequester more carbon than ploughed fields when soil depths greater than 30 cm are taken into account.

References

  1. Fernandez-Cornejo J, McBride WD. The adoption of bioengineered crops. Agricultural Economic Report No. 810. Washington, DC: US Department of Agriculture; 2002. Available at: http://www.ers.usda.gov/publications/aer810/aer810.pdf.
  2. Gurian-Sherman D. Comment on: Science, dogma and Mark Lynas. The Equation. http://blog.ucsusa.org/science-dogma-and-mark-lynas. Published January 24, 2013.
  3. Bindraban PS, Franke AC, Ferrar DO, et al. GM-related sustainability: Agro-ecological impacts, risks and opportunities of soy production in Argentina and Brazil. Wageningen, the Netherlands: Plant Research International; 2009. Available at: http://bit.ly/Ink59c.
  4. Neuman W, Pollack A. US farmers cope with Roundup-resistant weeds. New York Times. http://www.nytimes.com/2010/05/04/business/energy-environment/04weed.html?pagewanted=1&hp. Published May 3, 2010.
  5. Intergovernmental Panel on Climate Change (IPCC). Working Group III: Mitigation. A Report of Working Group III of the Intergovernmental Panel on Climate Change. Geneva, Switzerland; 2001. Available at: http://www.ipcc.ch/ipccreports/tar/wg3/index.php?idp=21.
  6. Baker JM, Ochsner TE, Venterea RT, Griffis TJ. Tillage and soil carbon sequestration – What do we really know? Agric Ecosyst Environ. 2007;118:1–5.