ngin - Norfolk Genetic Information Network

14 August 2002


As the editors of Nature in their Syngenta funded 'Nature Insight' on the "Food and the Future"[] have seen fit to reproduce Trewavas's anti-organic, "Urban Myths of Organic Agriculture," as one of their three Trewavas opinion pieces, published without any balancing comment, we thought we'd reproduce Angela Ryan's brilliant expose of how his propagandist claims are contradicted by the scientific literature.

for more on Trewavas:


Organics enter the science wars
ISIS News No 11/12 October 2001,
Institute of Science in Society,

Prominent scientists have been denigrating organic agriculture recently on both sides of the Atlantic. This debate has even reached the pages of  the top science journals. Angela Ryan reviews and rebuts the arguments put forward.
 Sir John Krebs, Head of the UK Food Standards Agency (FSA) said, "in my opinion and in the opinion of the FSA, consumers who buy organic produce are not getting value for money if they think they're buying food with extra nutritional quality or extra safety"[1].

Soon afterwards, as if on cue, an article appeared in Nature entitled, Urban Myths of Organic Agriculture, by Anthony Trewavas, Prof. of Plant  Biochemistry, Edinburgh University. It sets out to refute a common argument "that organic farming is 'holistic' and superior to reductionist 'chemical' agriculture".

This dichotomy is false, and "neither is superior". He claims "there is very little science to organic farming" [2].

Organic agriculture bans the use of synthetic pesticides, herbicides, fertilizers, fungicides, veterinary drugs (antibiotics, growth hormones), synthetic preservatives and additives, and irradiation, many of which are associated with harmful effects on health and biodiversity. Not only that, a United Nations Food and Agricultural Organisation (FAO) 1998 report on organic farming suggests considerations like ethical values and sustainable production principles are gaining weight in the food sector as "integral product values" for consumers [3].

The former UK Ministry of Agriculture Fisheries and Food (MAFF) 1998 Review examined comparative studies on biodiversity, and concluded,  "organic regimes have the greatest benefit for biodiversity at the farm level".

But according to Trewavas, organic farming practices do not "necessarily conserve the environment". He claims that "current synthetic pesticides  are very unstable; only transient declines of most field insects are reported even at full pesticide dosage". And conjectures, "lower levels of aphids observed on organic farms could well reflect lower nitrogen and protein content of organic crops".

A new study comparing arthropod communities and pest damage levels to fresh market tomato, Lycopersicon esculentum, was carried out on 18  commercial farms in California, representing a range of management practices, half operating as organic and half as conventional [4].

The study found that insect pest damage varied across the spectrum of farm management practices and organic and conventional farms did not  differ significantly for any type of damage to tomato foliage or fruit.

However, there was a significant difference between the actual community structures of arthropods. There was higher abundance of natural enemies,  and greater species richness of herbivores, predators, parasitoids and others in organic farms where arthropod biodiversity was one-third  greater.

Trewavas claims "developments in the past 25 years have shown how conventional agriculture can be much more sustainable and environmentally friendly than organic farming". He cites the Institute of Arable Crops Research (IACR) website as reference.

The scientific literature contradicts his claim. A new study in Nature compared the sustainability of organic, conventional and integrated apple production systems in Washington State from 1994 to 1999 and found the organic systems ranked first for environmental and economic sustainability, with the integrated second, and the conventional last[5].

The researchers measured soil quality, horticultural performance, orchard profitability, environmental quality and energy efficiency, which are all specific indicators of sustainability.

They found that all three systems gave similar apple yields. The organic and integrated systems showed higher soil quality and lower negative  environmental impact. But the organic systems produced sweeter and less tart apples, higher profitability and were more energy efficient. Tree  growth was similar for all three systems but analysis of fruit firmness at harvest and after storage showed that the organic fruit was firmer.

Environmental impacts were assessed using the rating index employed by scientists and growers. The total environmental impact rating of the  conventional system was 6.2 times higher than that of the organic system, and the integrated system was 4.7 times higher.

Energy accounting was divided into inputs (labour, fuel, fertilisers and so on), output (yield) and output/input ratios (energy efficiency).  Energy efficiency for the organic system was 7% greater than the conventional system and 5% greater than the integrated system.

Enterprise budgets were generated each year to calculate net returns from total costs and gross receipts. There was no price premium for integrated fruit but the price premium of organic apples averaged 50% higher than conventional prices. Hence, the organic system was more profitable.

The use of manure on organic farms results in higher, beneficial levels of biodiversity, especially earthworms, but Trewavas claims there are "numerous problems", including "possible effects on human health".

Manure is also widely used on conventional farms. Faecal matter is known to contain a range of human pathogens but properly treated manure is effective and safe. Furthermore, unlike conventional regimes, mandatory organic certification bodies inspect farms to ensure standards are being met.

Trewavas states, "ploughing in of legume crops on organic farms to improve soil fertility and continued manure breakdown leads to nitrate leaching into aquifers and waterways at identical rates to conventional farms".

The occurrence of nitrates is a major public health hazard as they can be converted to nitrosamines, which are carcinogens and nitrates impair the ability of blood to carry oxygen.

But FAO reports that nitrate content on organic farms is "significantly lower" due to absence of soluble fertilizers and the governments of Germany and France encourage conversion to organic farming in a bid to improve water quality in certain areas.

Furthermore, the use of 'biosolids' from wastewater treatment facilities (sludge) on conventional farms raises concern over heavy metals, toxic organic compounds, such as dioxin, PCBs and persistent microbial pathogen contamination. The Codex and EU organic standards prohibit the use of sewage sludge and the US National Organic Programme also bans it.

Organic regulations recommend hay for animal feeding, but Trewavas claims "hay-fed animals infected with Escherichia coli 0157 incubate this dangerous organism longer than conventional animals fed with grain".

FAO report that the US Centres for Disease Control (CDC) identifies the main source of E. coli infection as meat contaminated during slaughter.  Virulent strains of E. coli such as 0157, develop in the digestive tract of cattle that are fed mainly with starchy grain [6]. Cows fed with hay generate less than 1% of E.coli found in faeces of grain-fed animals. FAO concludes, "ruminants like cattle and sheep fed in the organic system reduce the risk of E. coli infection".

Trewavas writes, "food mycotoxins from contaminating fungi definitely contribute to European cancer rates, and fumonisin and patulin are both  reported to be higher in organic products". He claims "failure to use effective fungicides on organic farms has led to these farms acting as repositories of disease" and "organic farms may be protected from the full effects of disease outbreak because they are surrounded by conventional farms using proper fungicides."

Mycotoxins are toxic by-products of certain moulds that can grow on food. Since fungicides are not allowed in organic systems, many studies have investigated their presence in both organic and conventional foods [7]. From these, FAO conclude, "it cannot be concluded organic farming leads to an increased risk of mycotoxin contamination".

FAO report two studies that found aflatoxin levels in organic milk were lower than conventional, suggesting additional risks involved with feeding mainly grain to conventionally raised livestock. Aflatoxins are most toxic and can induce liver cancer at low doses if ingested over time. The report states, "as organically raised livestock are fed higher proportions of hay, grass and silage there is a reduced opportunity for mycotoxin contamination."

Several other hazards are associated with conventional food production. In Central and Eastern Europe, there are areas of high contamination due  to industrial activities, from mining, smelting, the energy sector, agricultural practices and disposal of hazardous and municipal wastes.

FAO reports, "A more widespread use of organic agriculture would contribute to a reduction of environmental degradation, ultimately resulting in reduced levels of contaminants in food". Furthermore, "EU member states increasingly see organic agriculture as a tool for improving rural economies and stability, while simultaneously increasing biodiversity and environmental sustainability".

It is clear that holistic approaches that link ecology and economics benefit both the ecosystem and human health, and are competitive in commercial markets.

[1]Urban Myths of Organic Farming, by Anthony Trewavas, Nature, Vol 410,
22 March 2001 pp 409-410

[2]'Nutritionists question study of organic food', Nature, Vol 412, 16th August 2001

[3]Twenty Second FAO Regional Conference for Europe, Porto, Portugal, 24-28 July 2000, Agenda Item 10.1, Food Safety and Quality as Affected  by Organic Farming, Available for download at

[4]D.K. Letourneau & B Goldstein (2001) Pest damage and arthropod community structure in organic vs. conventional tomato production in  California, Journal of Applied Ecology, vol 38, pp 557-570

[5]John P Reganold, Jerry D Glover, Preston K Andrews and Herbert R Hinman (2001), Sustainability of three apple production systems, Nature,  Vol 410, 19th April, pp 926- 930

[6]Couzin, J et al (1998) Cattle Diet Linked to Bacterial Growth, Science Vol 281, pp1578-1579

[7]Marx H, Gedek,B & Kallarczil, B (995) Comparative investigation of mycotoxicological status of alternative and conventional grown crops, Z  Lebensm Unters Forsch, 20, 83-6

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