GM Free Cymru

Home truths on GM Crops and Foods

Soil Association Press Release, 19 June 2008

Fact: GM crops don’t increase yields, do have negative health impacts

Against all the evidence and in direct opposition to the recommendations of his Chief Scientist [1], Gordon Brown, like his predecessor, is being bamboozled by PR from the Agrobiotech lobby that GM crops ‘can feed the world’.

Contrary to the claims of some government ministers that are ‘there are no scientific arguments’ against GM crops, there is a strong body of published evidence that shows GM crops do not increase yields and also indicating negative health impacts for livestock eating GM feed and potentially for humans consuming produce from those animals. This research is set out below. [2]

But the main argument against GM crops is that they reinforce an outdated model of agriculture that is wholly unsuited for adapting to and contending with the conditions that climate change and more costly, scarcer oil bring for global food security. [3]

Patrick Holden, Soil Association director said, "The GM industry is desperate to prove it offers any benefits beyond the self-interested, commercial one of locking farmers into dependency on its own patented seeds and linked inputs of pesticides and fertilisers. The evidence after decades of claims is that GM crops are no better and often poorer in terms of yields, and more worryingly that there are real animal and human health concerns.

"GM’s greatest flaw is that it reinforces agriculture’s inherently unsustainable reliance on vast inputs of fossil-fuel derived inputs in the form of fertilisers and pesticides – which are becoming economically, as well environmentally unaffordable. Poor farmers in developing countries cannot afford expensive chemicals and even big arable producers in the UK question their viability as fertiliser costs double in price to over £350 a tonne. [4] GM crops will add to climate change, by requiring the added inputs of the same old chemical fertilisers that consume half of all the energy used in agriculture, so giving off vast amounts of damaging greenhouse gases. [5]

"The Prime Minister would do better to listen to his Chief Scientist at Defra, Professor Bob Watson, who chaired the recent international agricultural assessment that concluded ‘business as usual is no longer an option’ and called for a shift to ‘agroecological’ food production. The assessment questioned GM’s claims to be the solution to global poverty, hunger or climate change and in contrast inclined towards organic, causing the GM representatives to storm out of the process." [6]


For media enquiries please contact Clio Turton, Soil Association senior press officer, 0117 914 2448 /


Notes to editor:

[1] Professor Bob Watson, Chief Scientist at Defra, chair of the International Assessment of Agricultural Knowledge, Science and Technology for Development (IAASTD). Previously Chief Scientist at World Bank. Leading expert on climate change. ‘Discovered’ the Ozone Hole whilst working at NASA.

[2] Scientific evidence of health impacts of GM crops: Despite GM industry claims, over a dozen GM feeding trials (12 animal, 1 human) show negative health impacts of GM: Russian rat trial of GM soya: high mortality and stunted growth in offspring (Ermakova, 2005) Italian mice trial of GM soya: metabolic effects on body organs (Malatesta et al, 2002 and 2003; Vecchio et al, 2004) FSA-commissioned human trial of GM soya by Newcastle University: GM DNA transfers out of food into the body’s gut bacteria (Netherwood et al, 2004) Monsanto rat trial of GM maize: changes in body organs indicating toxic effects (report by Monsanto, 2002; review by Dr Pusztai, 2004; Séralini et al, 2007) Aventis chicken trial of GM maize: mortality doubled and significant change in composition of meat (reports for the Chardon LL hearing, 2002; review in “Food safety – contaminants and toxins, CABI publishing, 2003) Aventis rat trial of the novel protein of GM maize: reduced body weight and metabolic effects (same references as for Aventis chicken trial) UK study on sheep: in a few minutes, the genes in the GM maize move into the bacteria in the mouth, changing their characteristics (Duggan et al, 2003) Monsanto rat trials of GM oilseed rape: reduction in body weight and increased liver weight (significant as the liver is the organ of detoxification) (US FDA, 2002; Opinion of the Scientific Panel on Genetically Modified Organisms, 2004) Australian mice trial of GM peas: allergic reactions, including inflammation of lungs (Prescott et al, 2005) Calgene mice trials of GM tomatoes: gut lesions and 7 of 40 died within two weeks (review in “Food safety – contaminants and toxins, CABI publishing, 2003) UK Government-commissioned rat trial of GM potatoes by Rowett Research Institute: gut lesions (Ewen and Pusztai, 1999)

NB: These studies were all designed to identify health impacts; the animal trials often referred to by the GM companies as ‘showing no negative impacts’ are largely irrelevant as proof of safety, because they are mostly studies carried out for commercial purposes on the efficacy of the feed, rather than ‘toxicological’ studies involving tissue analysis.


GM Crop do not increase Yields: the Science

GM crops in general Firstly, the current generation of GM crops were modified for insect resistance and weed control), not to increase the intrinsic yield capacity of the plant. An April 2006 report from the United States Department of Agriculture (USDA) states that “currently available GM crops do not increase the yield potential of a hybrid variety. In fact, yield may even decrease if the varieties used to carry the herbicide tolerant or insect- resistant genes are not the highest yielding cultivars”. (Fernandez- Cornejo, J. and Caswell, 2006) UN Food and Agriculture Organization 2004 report on agricultural biotechnology acknowledges that GM crops can have reduced yields (FAO, 2004). 2003 report published in Science stated that “in the United States and Argentina, average yield effects [of GM crops] are negligible and in some cases even slightly negative”. (Qaim and Zilberman, 2003). Yields of both GM and conventional varieties vary - sometimes greatly - depending on growing conditions, such as degree of infestation with insects or weeds, weather, region of production, etc. (European Commission, 2000)

Roundup Ready (RR) GM soya Studies from 1999 - 2007 consistently show RR GM soya to yield 4 – 12% lower than conventional varieties: A 2007 study by Kansas State University agronomist Dr. Barney Gordon suggests that Roundup Ready soya continues to suffer from a yield drag: RR soya yielded 9% less than a close conventional relative. A study by University of Nebraska agronomists found that RR soya varieties yielded 6% less than their closest conventional relatives, and 11% less than high yielding conventional lines (Elmore et al, 2001). This 6% ‘yield drag’ was attributed to genetic modification, and corresponds to a substantial loss in production of 202 kg/ha. In 1998 several universities carried out a study demonstrating that, on average, RR soy varieties were 4% lower in yield than conventional varieties (Oplinger et al., 1999). These results clearly refuted Monsanto’s claim to the contrary (Gianessi, 2000).

Yields of GM soybeans are especially low under drought conditions. Due to pleiotropic effects (stems splitting under high temperatures and water stress), GM soybeans suffer 25% higher losses than conventional soybeans( Altieri and Pengue, 2005) 5 studies between 2001 -2007 show that glyphosate applied to Roundup Ready soybeans inhibits the uptake of important nutrients essential to plant health and performance. The resultant mineral deficiencies have been implicated in various problems, from increased disease susceptibility to inhibition of photosynthesis. Thus, the same factors implicated in the GM soya yield drag may also be responsible for increased susceptibility to disease. (Motavalli, et al., 2004; Neumann et al., 2006; King, et al.,2001; Bernards,M.L, 2005; Gordon, B., 2007).

The yield drag of RR soya is reflected in flat overall soybean yields from 1995 to 2003, the very years in which GM soya adoption went from nil to 81% of U.S. soybean acreage. By one estimate, stagnating soybean yields in the U.S. cost soybean farmers $1.28 billion in lost revenues from1995 to 2003 (Ron Eliason, 2004).

More recent evidence shows that the kilogram per hectare ratio of soybean has been in decline since 2002, leading to the conclusion that RR soy does not have an impact on yield (ABIOVE, 2006a).

Bt Maize Only GM maize has shown a persistent trend for yield increase, but even here the rate of increase is no greater than those being achieved by conventional varieties. A US study conducted under controlled conditions demonstrated that Bt maize yields anywhere from 12% less to the same as highly similar, but conventional varieties (Ma & Subedi, 2005).

Bt Cotton Despite the claims, Bt cotton has delivered no significant impacts in real terms: Average cotton yields have increased 5-fold since 1930, surging from 1980 to the early 1990s. Cotton yields then went flat, and stagnated during the seven years of GM cotton’s rise to dominance. The steep yield and production increases in 2004 and 2005 were chiefly attributable to excellent weather conditions (Meyer et al., 2007). Bt cotton, introduced to Australia in 1996, has not offered a boost to the cotton sector, and since its adoption has not provided improvements in either yield, or quality (ISAAA, 2006b). Cotton South Africa show constant yield levels before and after adoption of Bt cotton (Witt et al 2005, cited in FoEI Who Benefits 2007), in contradiction to ISAAA claims that Bt has brought about a 24% yield increase in the region. Outbreaks of the secondary pests that are not killed by the Bt insecticide have rendered Bt cotton ineffective in China (Connor, S., July 27, 2006), and are also becoming a problem in North Carolina (Caldwell, D. 2002) and Georgia (Hollis, P.L., 2006). An article in Nature Biotechnology notes that the poor performance of Bt cotton varieties used in India (which were developed for the short U.S. growing season) is linked to the loss of their insecticidal properties late in India’s longer growing season, and because Bt cotton insecticide is not expressed in 25% of the cotton bolls of India’s preferred hybrid cotton varieties (Jayaraman, K.S., 2005)

[3] Agriculture, like all sectors, must cut its greenhouse gas emissions that drive climate change by 60-80%. Detailed studies of ten agricultural sectors by Cranfield University for Defra, and earlier studies of five other vegetables, show that organic farming uses on average around 26% less energy per tonne of output than conventional systems

[4] In the UK, the price of nitrogen fertiliser has doubled over the past year to around £330 per tonne. With oil currently at over $130 a barrel and with OPEC warning it could reach $200 by the end of the year, it has been suggested that the price of fertiliser could hit £500 a tonne. At these prices, the claimed efficiency of fossil-fuel and fertiliser dependent industrial farming begins to collapse.

[5] The environmental imperative of cutting greenhouse gas emissions by 60-80% across all sectors to curb dangerous climate change already make intensive agriculture’s dependence on nitrogen fertiliser unsustainable: The manufacture of nitrogen fertiliser is the main use of energy in agriculture, accounting for 37% of total energy use Agriculture in the UK, 2004 Globally agriculture is the single largest source of the powerful greenhouse gas, nitrous oxide – over 310 times more damaging than carbon dioxide For each tonne of fertiliser made 6.7 tonnes of carbon dioxide equivalent greenhouse gases are emitted Fertiliser manufacture is also a major user of water, requiring 37 tonnes of water to make 1 tonne of nitrogen fertiliser

Organic farming does not use artificial chemical fertilisers, instead building soil fertility through crop rotations and particularly the use of clover that fixes nitrogen naturally from the atmosphere using the Sun’s energy and photosynthesis. Clover can fix 200 kg of nitrogen per hectare over a year. Average applications of N fertiliser across all arable and grassland are 110 kg/ha (arable = 150kg/ha; grassland = 77kg/ha). Fertiliser Statistics, 2005 report, AIC) 6. ‘Representatives of the biotechnology industry, for example, stormed out of the negotiations earlier this year, arguing that the potential of GM crops to help poor farmers and comabat global warming was being overlooked and undue weight given to alternatives such as organic farming,’ NewScientist feature on IAASTD report, 5/4/08.


For full references for note [2] above please see the following press release: 'Soil Association report shows GM crops do not yield more - sometimes less 848d689047cb466780256a6b00298980/3cacfd251aab6d318025742700407f02!OpenDocument