Trees against deserts

  • 14/02/2000

Trees against deserts traditionally, human beings have been forest-dwellers - cradled in the tropics and surviving on the fruit of the trees. The garden was a clearing in the forest where vegetables were grown. Folklore and legend describe how trouble first came when humans gave up the garden culture and became a herdsfolk. To raise livestock, fields were enlarged, more forests were cleared and, frequently, the water cycle was broken. In time, as cities grew, pressure on land increased. It took time for humans to recognise the connection between tree cover, on the one hand, and the growth of food crops and desertification on the other.

Today, of the Earth's 12 billion hectares, more than 3.6 billion hectares are already desert. Land is being lost to deserts much faster than it is being reclaimed. Humans have a bad record as forest destroyers, cutting and burning greedily and recklessly, destroying the fertility of the soil accumulated through the centuries.Even in countries like usa , up to three-quarters of the land has been degraded by growing crops to feed animals which are, in turn, killed to feed humans.

Trees are needed to fix the soil and lift the water table and keep the land cool. The tree cover has to be restored to fix the soil and prevent quick runoff of water. The leaf-fall and humus on the floor of the forest will act as a sponge to retard quick-run off after a storm. Water will sink through to porous soil and form myriads of springs that feed the land and the rivers during the drier months of the year. Mountains and high-ground should be covered with protective forests up to the snowline. So by being responsible for the formation of humus and enriching the soil by the minerals that have been carried up to the leaves in the rising sap, trees give back to the earth more than they take.

To prevent deforestation in the tropics, the best way is to replant trees around fields. It will return fodder to the cattle, fruit and wood to the inhabitants, fertility to the soil and pure water to the rivers. Forests will increase naturally where there are mine-fields, depopulation and insecurity. Tree fellings cause a drop in the rainfall. Besides, planting shelter belts and shade trees help increase food production up to 100 per cent. The shade leads to a lower yield of the crops close to the trees, but it increases overall. A 1986 Food and Agriculture Organization (fao) study on the wind-break effects confirmed these results.

We do not need interdisciplinary researches but an interdisciplinary reflection. We must not speak of forests, deforestation and reafforestation but of trees, their destruction or their planting around fields, along river and canal banks. The rights of trees are linked to the rights of humans. The new alliance between humans and trees will begin with agroforestry, which should be written agro-treedom or as the equation field-tree partnership = organic agriculture + trees.

The Germans were regarded by the British as the leading foresters in Europe. Early in their history, they had been alerted to the necessity of maintaining tree cover in high country. When Alemanni tribes entered Germany from the south, they came to suffer from serious drought, accelerated erosion and desiccation. Some of the Alemanni, recognising the value of leaving the forest intact, had made only small clearings for the cultivations which they worked in rotation, allowing the trees to re-establish themselves. This led to a simple form of forest management that was retained through the ages. After Leonardo da Vinci had developed the first principles of forestry in France, the Germans had systematised them and, with scientific and mathematical precision, had developed schematic silviculture systems of an advanced nature. So, it was to Germany that generations of forestry students of India went to get their practical experience.

Under existing systems, food looms large and there is a constant threat of famine over wide areas, but if we treat reafforestation as seriously as we do national defence, and turn from an animal economy to a sylvan one, we would be able to look forward confidently to the time when food will not be a problem.

The author is an engineer based in France

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