Royal Agricultural Society of England

Field of Genes

As a biologist and science writer who has watched the development of genetic engineering from the start, I see genetic modification (GM) as just the latest technology to serve the massive intensification of agriculture. There is nothing new about either the benefits it promises or the risks it threatens, many of which are already upon us.

For example, farmers have been spraying herbicides and insecticides for decades, wiping out anything they think competes with their harvests. Naively, one thinks a bumper harvest makes for a happy farmer. In reality, the farmer does best out of scarcity, as the Porter in Macbeth knew full well: Knock, knock, knock! Who's there, in the name of Beelzebub? Here's a farmer that hanged himself on the expectation of plenty.

Plenty pushes prices down. Best for the farmer is to have plenty in a time of general scarcity. The farmer who can afford to protect a crop from pests will more than recoup his costs by selling into a short market; but that is true for all farmers. The result is an upward spiral in which all farmers are using more pesticides than they should be, biologically and economically. This undermines the value of the pesticides, and means the farmers often fail to recoup their costs. Worse, it squanders the pesticide by selecting for resistance.

For pesticide performance, the darling of the genetic engineers is a bacterium called Bacillus thuringiensis, or Bt for short. Organic farmers like it, too, because it is a natural product and therefore must be good. However, several economically important pests have become resistant to Bt - not because they feasted on crops that had been genetically modified to make Bt toxin, but because in their efforts to eradicate Bt, farmers overused ordinary, old-fashioned pesticide spray.

Warning signs about the resistance of Bt appeared in 1986 on the island of Oahu in Hawaii. A watercress grower noticed that some diamondback moths in his field were not succumbing to Bt. Experts at the University of Hawaii decided the numbers involved were insignificant, and the farmer continued to spray. By 1989, three years later, the proportion of resistant moths had doubled. Moths resistant to Bt had turned up in another watercress field on Oahu, and in a cabbage field on the big island of Hawaii. Resistant moths appeared in Thailand, the Philippines, Japan, Florida, and New York. In every case, the growers were using frequent, high doses of Bt. One sprayed 15 times in a single year.

Plant diseases have become resistant in exactly the same way, with no help from genetic manipulation. Government and industry have tackled the question of resistance by drawing up management plans and hoping these will do the trick. Take Bt, for example. In 1996, corn engineered to express the Bt toxin accounted for less than 1 percent of all U.S. production. By 1998, it had risen to 19 percent - 4.2 million acres. The risk of selecting resistance is greater than with a spray, because Bt is present all through the season and in all the plants, instead of temporarily and patchily.

Novartis Seeds, an industry leader with its Bt corn, offered a financial incentive to help farmers make the tough decision to forego certain methods of pest resistance. Novartis offers growers substantial savings if at least 20 percent of each order includes non-Bt hybrids. The idea is that farmers will create refuges of non-Bt corn, where susceptible pests can survive and thrive, mating with occasional resistant specimens. (But only if they buy all their seed from Novartis.)

The irony is that, having seen the value of Bt corn, farmers are unwilling to sacrifice a single ear. The National Corn Growers Association noted that if the refuge requirements are too onerous, growers will not be able to justify using the technology from an economic perspective. One Canadian farmer said the refuge strategy would fail because no farmer will pay a premium price for Bt hybrids if he has to plant junk hybrids on 25 percent of his acreage. Most progressive farmers, he said, would buy and plant the new hybrids edge to edge and leave it to their less progressive neighbors to stick with the older, cheaper varieties lacking the Bt gene. To date, farmers have shown no evidence of having the greater good at heart; and why should they, when (as in other industries) they tend to reap profits themselves, while society at large pays the costs?

I have dwelled at some length on issues of pests and diseases, but one can detect the same pattern - conventional agriculture got there first - in all other concerns about GM food. Some protesters worry about a gene smog - the uncontrolled dispersion of modified plant genes across long distances. But pollen has always traveled, and unless the conventional crop is being raised to produce fresh seed (in which case, contamination is something the farmer ought to be on guard against no matter what its source), the fact that the pollen is from a genetically modified plant presents no additional hazards.

Drivers along Britain's roads can already marvel at conventional genetic pollution. Smears of the brilliant yellow flowers of oilseed rape (Brassica napus) are a familiar sight wherever grain lorries have spilled their unmodified seed. That, and the spread of agriculturally improved varieties of wildflower, are clear evidence of genetic pollution that owes nothing to genetic engineering.

Conventional agriculture has also already managed to realize yet another of the big fears: superweeds, resistant to all the pesticides one can throw at them. In Manitoba on the Canadian prairies, two-thirds of the cropland has patches of wild oats resistant to two or more classes of herbicide. In 1997, triple- and quadruple-resistant oats appeared. Weed scientists with Agriculture and Agri-food Canada blamed farmers who ignored advice to rotate crops and herbicides.

In 1996, an annual ryegrass resistant to glyphosate appeared in Australia. It was the first resistant plant species in 20 years of glyphosate use. Some Australian populations of annual ryegrass can now survive all herbicides registered for their use. Goosegrass has become resistant to dinitroaniline herbicides such as trifuralin and oryzalin. Scientists finally understand at a detailed molecular level exactly why they are resistant. (They proved this, incidentally, by manipulating the mutant gene into maize to make it resistant, too.) But as the researchers point out, in the wild this resistance has arisen, and been selected for, as a result of repeated exposure to this class of herbicide.

A final fear is that eating GM foods can be dangerous. Again, GM foods pose no new threats. The intensification of the food supply industry has contributed to the safety (or lack thereof) of ingredients and food in many ways. A simple example: Feeding cattle grain considerably increases the number of Escherichia coli bacteria in their guts, and those bacteria are more resistant to acid than E. coli from grass-fed cattle. Because they are more numerous, the E. coli from grain-fed cattle are, all else being equal, more likely to make their way into the human digestive system. They are also better able to resist acid attack, and more likely to survive their trip through the stomach. If they are of the virulent strain 0157, the result can be fatal.

Cattle are fed grain because it is cheaper and more fattening than hay, but farmers do not have to abandon grain feed (and consumers do not have to stomach the increase in meat prices that would accompany a switch back to grass). Feeding cattle hay or silage for five days before slaughter greatly diminishes the number of acid-resistant E. coli in the gut.

It is also worth bearing in mind that the human diet contains a huge number of entirely natural, unselected items that are extremely unsafe if not properly prepared. People with nut allergies may react very badly to a GM food or ingredient that contains genes from nuts. But they have always run the risk of unwanted pieces of nut finding their way into, say, chocolate bars. The issue is one of information about the food, not of the processes that created the ingredients.

GM crops pose no potential threats that intensive agriculture has not already made a reality. But because opponents have focused on scientific worries, the biotech industry has been able to respond by trying to show that those fears are groundless. The results on both sides have been pretty unedifying. Basing an argument on the desire for scientific certainty, especially in a culture that understands neither statistics nor risk and has not embraced the precautionary principle, always permits one's opponents to come up with countervailing conclusions. My suspicion is that the opposition to GM crops is actually much more emotional and less scientific than most people will admit.

Opponents of GM food crops should come out with it and admit that they just don't like the idea. Farmers would do well to stand back and ask whether they cannot reap the benefits offered by GM crops by using other techniques, with the added gain of supplying products people might actively prefer (for whatever dubious reasons).

Jeremy Cherfas has a Ph.D. in animal behavior but is a now a freelance journalist and communicator by trade. He has been biology editor of New Scientist, European correspondent of Science, and a reporter for several BBC Radio Four programs about agriculture and the environment.

(Edited version of a contribution to Old Crops in New Bottles? Six Thoughts on the Science of Genetically Modified Crops, published on December 2, 1998 by the Royal Agricultural Society of England.)