The 'GM helps climate change' myth unravels

September 2014

Photo of tractor applying fertiliser to an untilled field
Fertiliser applied to no-till field in US.
CC photo By Lynn Betts [Public domain], via Wikimedia Commons
In contrast with the traditional ploughing-under of weeds before the sowing of seeds, no-till agriculture involves destruction of weeds on the surface then planting of seeds in grooves or holes with minimal disturbance to the soil.

There are several recognised benefits of no-till. In particular, valuable soil structure is preserved, reducing erosion and increasing important biological activity, plus the retained plant-matter holds more water. For the farmer, no-till means reduced labour and fuel costs.

Also, because breaking up the soil by ploughing triggers a loss of the carbon locked up by soil organisms, no-till has become part of the solution to climate change (see below).

Although GM herbicide-tolerant crops are not, in fact, the only way to farm without ploughing, the biotech industry has long marketed them as enabling no-till, and helping to save the world from climate change.

In 2012, biotech industry consultants managed to conclude that “Crop biotechnology has contributed to significantly reducing the release of greenhouse gas emission from agriculture practices. This results from less fuel use and additional soil carbon storage from reduced tillage with GM crops. In 2010, this was equivalent to removing 19.4 billion kg of carbon dioxide from the atmosphere or equal to removing 8.6 million cars from the road for one year.”

By 2014, these claims had hyperboled into “The use of biotech crops has led to saving about 27 billion kg worth of carbon emissions that could have been released in the atmosphere if the technology did not exist ... This is equivalent to taking 12 million cars emitting carbon dioxide and other greenhouse gases off the road”.

Years before such grand figures emerged from its consultants, Monsanto was trying to claim carbon credits for no-till agriculture using its Roundup herbicide and GM crops [1].

Even the UN, in a 2013 report from its Environment Programme, restated the claim that “changing to no-till practices in agriculture, as an alternative to conventional tillage, causes an accumulation of organic carbon in soil, thus mitigating climate change through carbon sequestration.”

However, a recent review of the evidence, including a critical look at the bases on which the data were collected, has seriously questioned the climate-saving potential of no-till.

The authors pointed out that measurements have been largely restricted to the top few centimetres of soil. In a no-till system, the soil surface is largely dead plant-matter with very little solid soil particles mixed in. Readings taken down to 20 cm from the surface will suggest a very high organic content. However, if the measurement depth is doubled, the total proportion of organic matter is actually little different from a tilled system. What this means is that carbon is not being sequestered in the soil, and moreover, that most of it is located where it will easily be lost to the atmosphere (especially in the event of occasional ploughing which is often part of a no-till regime).

The timing of the measurements can also lead to false conclusions. Realistically, carbon accumulation in soil will quickly reach its maximum. This means that the rapid rates of carbon increase recorded in the early years after a switch to no-till can't be extrapolated very far into the future.

It was also noted that the positive UN report was heavily based on a 2010 current status report of no-till globally. This study was primarily a comparison of opinions on no-till in different regions of the world with virtually no data on soil organic carbon.

The review concluded that although “There are some genuine opportunities for mitigating climate change in the agricultural sector, largely through improved management of water and nutrients - especially nitrogen from fertilizer and manure - and through improved feeding practices and management of ruminant livestock”, the global potential for soil carbon sequestration has been overstated.

As Professor David Powlson of Rothamsted Research said:
“Over-stating the climate change benefits of no-till is serious as it gives a falsely optimistic message of the potential to mitigate climate change through altered agricultural practices”
and stressed the need to “decrease greenhouse gas emissions from other aspects of agriculture and from other sectors of human activity”.


The 'too short, too shallow' theme seems to be recurrent in all safety and environmental testing carried out on GM crops.

No-till practised appropriately (for example, not in soils prone to water-logging) is a beneficial agricultural technique. Achieving no-till by using a toxin, such as the glyphosate herbicide widely used on GM crops, which becomes sequestered by attachment to soil particles and is damaging to the biological activity of the soil, is not good practice.

Using the same GM-crop/herbicide packages with no-till year-on-year props open the door to plant disease.

GM crops are aimed at high-tech farming systems with an inherent high dependency on climate-damaging chemicals produced using fossil fuels. The idea that factoring in no-till to an inherently damaging system will somehow make them OK is a scam.

Next time you hear the media trotting out biotech industry claims that GM will help climate-change, don't hesitate to pour some cold water on it.



Agriculture's contribution to climate change

In 2013, the level of carbon dioxide in the atmosphere reached 400 parts per million for the first time in human history. 

Soil is capable of sequestering carbon captured from the air, but can release it again.

The carbon locked up on soil organic matter in natural areas is huge, estimated to be three times the amount of carbon (as carbon dioxide) in the air.

Clearance of forests for expanding agriculture has led to significant losses of the carbon sequestered in their soil, and to increases in carbon emissions. 

Organic farming systems have been show to increase the organic matter in soil, but decades of intensive agriculture have done just the opposite.

Besides direct damage to our food crops from destabilised weather patterns, a recent study has found that higher carbon dioxide levels reduce the levels of essential nutrients in important crops. For example, wheat grown in an atmosphere of higher carbon dioxide had 9% less zinc, 5% less iron and 6% less protein rice. Maize and soyabeans showed similar results.


  • David S. Powlson, et al., 2014, Limited potential of no-till agriculture for climate change mitigation, Nature Climate Change, 4 August
  • GMO climate change myth bites the dust, GM Watch 1.08.14
  • Limited potential of no-till agriculture for climate change mitigation, Farming Online, 31.07.14
  • Rob Percival, Nutrient deficit, Living Earth Autumn 2014

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