A quick fix

The tension between agriculture and ecology shows up clearly in the current debate over transgenic crops. In 1999, about 40m hectares of genetically engineered crops were grown by a dozen countries, a 44% increase on the previous year (see 7). Most of the crops were bred to resist herbicides, such as Monsanto's Roundup, or to produce insecticidal proteins, known as Bacillus thuringiensis, or Bt, toxins. Such genes are now found in a variety of commercial crops, such as soyabeans, maize, canola (oil seed rape) and cotton, increasingly put together in one plant. Their corporate purveyors promised higher yields with better pest control and lower expenditure on chemicals.

The technology has yet to deliver on all its promises, but has provided enough benefit to keep farmers planting. Four years after their launch, these crops have been taken up by farmers far more rapidly than the previous wonder, hybrid corn. Whether the inbuilt chemical protection of such genetically modified crops has reduced the use of pesticide is highly contested. A new study by Leonard Gianessi and Janet Carpenter at the National Centre for Food and Agricultural Policy in Washington, DC, seems to bear out both the hopes of farmers and the fears of environmentalists. It finds that in 13 American states that have been growing transgenic soyabeans, herbicide applications per acre have fallen by 9%, but 14% more herbicide is being used in total because acreages have expanded as well. And genetic modification has not increased yields.

"Post-emergence" herbicides such as Roundup, also known as glyphosate, work by killing all the plants in the field, both weeds and crop: the point of the genetic modification is to make the crop plants resistant to the chemical. This should eliminate the need for tillage, thus reducing mechanical damage to the soil. Gordon Wassenaar, who has been growing soyabeans in Iowa since the 1950s and remembers the bad old days of the highly toxic pestkiller DDT, is puzzled by the objections to GM crops. Like other farmers, he finds glyphosate much safer. "It beats me how to please these environmentalists. As soon as we meet one bar, another goes up."

Ecologists such as Margaret Mellon at the Union of Concerned Scientists worry that genetic modification not only perpetuates the problems of intensive agriculture but also adds new ones. They fret about the dominance of one "broad-spectrum" herbicide that both reduces the biodiversity in a field by killing all the plants and causes a few hardy weeds to develop resistance. They also fear, not unreasonably, that the added gene might be transferred from the crop plant to relatives in the field.

American maize farmers like Bt plants, crediting them with keeping levels of their chief pest, the European corn borer, so low as to benefit both GM and unmodified varieties. But such transgenic crops are even more troubling to environmentalists who fear they will also make pests more resistant. Last year, the news that pollen containing one of the Bt genes can stunt or kill Monarch caterpillars enraged butterfly enthusiasts around the world. The equally lethal effects on green lacewings got much less publicity, yet these insects do a useful job by feeding on the corn borer. Researchers have also shown that Bt toxins of the sort produced by the transgenic plants stay in the ground longer than expected, and may kill local insects and soil organisms. But these experiments were carried out in the laboratory. Real-life results are less alarming, but more tests are needed.

Some of agriculture's most serious environmental problems -- such as lack of water -- can be eased with technical solutions. Parched countries like Israel have mastered a number of neat tricks -- such as using a continuous drip of salt or waste water -- to make crops grow better. But how to encourage others to adopt such practices?

Most countries have relied on a mixture of regulation and prohibition to deal with environmental offences, such as taxing pesticides, penalising the discharge of manure and removing fertiliser subsidies. Both the European Union and America make direct payments to promote the use of less intrusive forms of cultivation and the setting aside of land. This is designed to cut production but has welcome environmental side-effects. On the whole, however, carrots for good ecological behaviour are less common than sticks for bad.

An exception is water marketing. Irrigation water is rarely priced at its real value, but without a price tag it is often wasted. In Chile, Mexico and California, however, farmers are able to trade "water rights" -- allocated by the state -- to those in need, such as industry. This seems to encourage farmers to invest in water-saving technologies so they can sell some of their rights, rather than quit altogether.

Having it all

Many ecologists, not content with improvements in conventional farming, would like to see completely new ways of farming adopted. Or, rather, old ways, going back to the traditions of half a century ago, when yields in the industrialised West depended more on nature and labour, and less on artificial aids. A mix of crops, trees and ground cover, rather than monocultures, helped buffer pest infestations and severe weather. Nutrients were recycled from livestock to crops. Nitrogen was introduced into the soil by rotating the main field crops with pulses. Rotation also helped keep down insects, weeds and diseases by breaking their life cycles. This kind of farming caused less environmental degradation than today's intensive, highly specialised agriculture, which produces much higher yields but may prove hard to sustain in the long term.

Those who advocate going back to agriculture's roots argue that their approach -- known as agro-ecology -- is just as scientific as the latest GM technology, because it relies on a detailed understanding of the complex interactions between soil, water, plants and animals. Miguel Altieri, an agro-ecologist at the University of California at Berkeley, points out that this is not the same as much of modern organic agriculture, which still largely relies on monoculture.

But in a world of industrialised farming, agro-ecology is hard to put into practice, if only because of the vested interests of agribusiness. One company that is easing itself towards encouraging this kind of agriculture is Unilever. For the past two years the Anglo-Dutch giant has been running pilot projects with growers to spread expertise around the world. It has found, for example, that natural forest left among its Kenyan tea plantations harbours insects that keep nasty bugs in check and acts as a windbreak, as well as providing fuel for the locals. This technique is now being passed on to the firm's plantations in India. Producers venturing into agro-ecology hope that it will lower their costs in the long run. But conversion is expensive, and although consumers say they want "clean, green and pristine" agriculture, they are not always willing to pay a higher price for it.