It may prove to be the tropical agriculture equivalent of turning water into wine - a new cultivation technique that allows "slash and burn" farmers to grow crops on the same plot of land for many years instead of constantly opening up new areas of forest.
Slash and burn farmers scrape a living by cutting down and burning patches of forest in order to grow crops on the cleared areas. After a year or two without forest growing on it, the soil quality becomes too poor to support crops, and the farmers have to move on - at which point the cattle ranchers and soya farmers move in. The sheer number of slash and burn farmers, however, has turned a once sustainable type of agriculture into a major cause of rainforest destruction and species loss. In the Brazilian Amazon alone, an estimated 500,000 small farmers are each clearing an average of one hectare of forest per year.
But a groundbreaking technique, called "Inga alley cropping", means that farmers do not need to keep moving on, but can maintain soil fertility, prevent weed growth and grow their crops more easily.
"The system simulates what tropical forests do naturally," says tropical ecologist Mike Hands, who has developed the technique at Cambridge University over the past 20 years. "It provides a layer of decomposing matter on the soil surface and recycles nutrients."
Inga is a genus of small, tough-leaved, nitrogen-fixing tree adapted in Latin America to race up to the light. Alley cropping is like planting crops be tween hedgerows. Put the two together, and the thick mulch formed by the leaves of the trees stops rampant invasion of grass and weeds, while allowing the crop to grow through.
Although alley cropping has been widely used, it has not been done with the Inga tree, whose leaves were thought to be too tough to break down quickly. "Inga was rejected by the original alley-cropping researchers because they thought it was too tough and wouldn't decompose quickly enough," Hands says. "But to stop weed growth, you've got to smother the ground completely."
Following six-year experimental trials, funded partly by the EU, Hands worked with farmers in Honduras. "We offered 30 farmers the opportunity to try out the scheme on small areas of their land," he says. "The trials were big enough to make a point, but small enough not to put their livelihoods at risk. All 30 are now either expanding or looking for more seed in order to expand, and all are in their third or fourth year of cropping basic grains. More than 4,000 other farmers have been shown the system at work and the response has been really positive - they were all clamouring for seeds, seedlings and technical assistance. We didn't have enough Inga seed to respond to the demand."
The system is popular with farmers, he says, because it offers them food security. By growing crops on a fixed plot of land near their dwelling, they no longer have a typical walk of two or three hours to reach the temporary site they are cultivating. Other family members can help out, and the crops can be more easily nurtured and guarded. The system also produces a plentiful supply of firewood, and it is less time consuming.
Battling against weeds is also very time consuming: "One farmer had been spending 160 man days a year just cutting weeds with his machete, just to get a crop to eat," Hands says.
Although the system can potentially be used by millions of farmers worldwide, Stephen Jennings, tropical rainforest ecologist at ProForest Consultancy, says there are two factors that can put slash-and-burn farmers off adopting new schemes. "First, if people have no reserves of food or money they have to keep slashing and burning to get a quick crop," he explains. "And, second, the poorer they are, the more conservative they tend to be."
But Hands claims that the rewards are already showing, as farmers plant higher value crops. "One family has made over $1,000 (£560) to date from black pepper they've grown, processed and sold," he says. "Farmers can raise two fingers to the banana or palm oil plantation companies who are atrocious exploiters of labour."
The plantation monocultures are a major cause of deforestation and, as they expand, they force slash-and-burn farmers on to less favourable land. "There are vast mountain ranges - in Honduras, for example - that have been totally stripped of forest," Hands says. "It is common to see people trying to farm 45-degree slopes. What forest is left is fragmented, so the door is closed on any real regeneration."
More farmers using Inga alley-cropping, he says, would reduce the demand for cultivatable forest areas, leaving virgin forest untouched and letting degraded forest recover.
Inga cropping is not a magic cure, however. Supplies of Inga seed are limited at present, and further funding is needed. "We need to set up seed banks so more farmers can get started, and we need more demo farms," Hands says. "The system doesn't offer a quick fix, but farmers keep telling us they've found it worth the effort."
On a larger scale, says David Boshier, senior research associate at the Oxford Forestry Institute, the problems are immense. "This offers an alternative in areas where you have slash-and-burn agriculture going on," he says. "But it takes 10-20 years for things to filter through. If you started tomorrow, with some Honduran farmers, within four years you still wouldn't have slowed the deforestation rate in the Amazon.
"Donor countries are deluding themselves by throwing peanuts at these problems and expecting massive results. Hands is making a difference to individual farmers in a certain area, which is massively important, but if you are talking about solving it on a global scale then you need big changes in the way governments operate. Rather than throwing £5m at it over four years, you must throw the £5m at it over 10 years."
· More details from: mikehands@UK2.net