May: concerns for the countryside.

No-one would lightly accuse Sir Robert May, the British government's chief scientific adviser, of being a romantic. The Australian-born theoretical-physicist-turned-population-biologist has established a powerful reputation for applying mathematical modelling to problems ranging from the preservation of biodiversity to the spread of AIDS.

His pragmatism has been well to the fore during the recent British controversy over the potential health effects of GM foods. A willingness vehemently to criticize the unscientific nature of many of the claims being made turned him into a key spokesman for the government. Equally passionate was his dismissal of the popular newspapers whose reports were fanning the controversy over so-called ‘Frankenstein foods’ as “straight entertainment”.

Where May does have concerns is about the long-term implications of GM-based agriculture on biodiversity. He points out that the history of agricultural change is in the direction of growing crops “that no one eats but us”. This has obvious consequences for the animals that also depend on the fields we use. May quotes, for example, recent surveys of the decline of many bird populations, and says he is convinced by evidence for corresponding effects on invertebrate and plant diversity. “The thrust of GM crops is to accelerate this trend.”

May admits that there remain scientific uncertainties about the health and environmental effects of GM food and crops. But he has little time for the claims by Scottish researcher Arpad Pusztai to have detected a depressed immune response from eating potatoes genetically engineered to produce the toxin lectin.

“That is not scientific uncertainty; as long as it remains unpublished, it is outside the canon of science,” says May.

May is confident that, if there had turned out to be such a danger with existing GM foods, Britain's regulatory authorities would have picked it up. But he also points out that the experience with bovine spongiform encephalopathy has brought home the need to expect the unexpected. “We must test,” he wrote in a paper for the Prime Minister Tony Blair. “No-one was looking for untoward effects in cattle. In the case of GM food, we are testing for unexpected and unwanted effects on health and the environment.”

Some widely quoted risks are, he says, relatively low, even if undesirable. One is the spread of ‘superweeds’ resulting from the interbreeding of herbicide-resistant crops with wild relatives. Although admitting that this could happen, he argues that the weeds would remain vulnerable to other herbicides.

Of slightly greater concern, he says, is possible cross-pollination with other crops. “We need to know rather more about this than we do at present.”

His real worry, however, is about the impact of GM crops on biodiversity. “We need wider mechanisms to reconcile farming with preservation of the countryside,” he says. “There is a much larger role for trying to understand how subsidies and other instruments interact with environmental protection.”

But May is adamant that the remaining uncertainties provide a basis for field trials “on a scale sufficient to answer the questions we face” — not for a moratorium on trials.