II.8: AGROFORESTRY

For thousands of years it’s been assumed that farming and trees don’t go together. But for many hundreds of years too farmers and growers of many kinds in many countries have been integrating trees with farming in many ingenious ways with many kinds of advantage. Farming combined with the serious culture of trees to the benefit of both, is called agroforestry.

Many different species of tree (or other woody perennial) are pressed into service in many kinds of arrangement. Alley cropping is geometrically simple, with rows of trees about 18 or so metres apart, with scope for any kind of husbandry between: arable, livestock, and all manner of horticulture. In one example in the flat lands of eastern England the rows of trees include hazel and willow for quick growth and immediate use; fruit trees; and hardwoods for long-term investment. On hills in many systems worldwide the trees are grown along the contours to help contain the flow of water and so reduce erosion and the risk of flooding below. Always, traditionally, in many parts of the world, there are or were copses at the tops of hills to take the brunt of heavy rains.

Contrary to expectation, the yield even of arable crops between alleys of trees is not significantly reduced, provided the trees are oriented so as not to cut out too much light. The microclimate that trees create can be of benefit: wheat in the middle of open fields, even in Britain, can be heat-stressed. Organic farming becomes easier as the trees serve as “beetle banks”, full of potential predators of pests. Livestock benefits from the shade and (when the trees are big enough to withstand some onslaught) from browsing their leaves, twigs, and fruits. All domestic species apart perhaps from sheep are basically woodland animals. The black pigs among the cork oak forests of Portugal and Andalusia give the finest ham in the world and dairy cattle in woods in Costa Rica may give 30% more milk than in open fields. If there is some loss of yield in individual crops this is made up for by the principle of “land equivalence ratio”: the value of trees and crops combined is greater than either trees or crops would give from the same area if grown as monocultures. Clearly, too, the trees can be enormously rich in wildlife. The East Anglian farm mentioned above is rich in voles. Barn owls have returned to prey on them and bumblebees nest in their vacated burrows.

Small wonder, then, that more and more farmers and agriculturalists worldwide are now adopting agroforestry. This is one of the few bright stars on an otherwise largely dismal horizon. (So far the British government has failed to take a positive interest, presumably because agroforestry does not offer immediate cash returns. But we cannot afford to wait for governments).