Soil Conservation Is World-wide Problem

Press, Volume XCVIII, Issue 29068, 3 December 1959, Page 24

Soil Conservation Is World-wide Problem

[By ANTONIO DE GAMARRAI

The huge dams and hydro-elec-tric schemes that have sprung all over the world during the last few years are proof of the progress made in the rational use of water and soil conservation. New land has thus been made available for agriculture and stock-raising. But in spite of these achievements, experts are pessimistic about the future: according to present-day estimates, the world population should double in the next 50 years, and this implies tremendous growth in food resources.

That is why science has begun to look into the problem of reclaiming land which is now lying waste; and today scientists from many different countries are studying the climate, the flora and fauna, and the composition of the soil in the arid and semi-arid regions which cover a third of the world's total land area. During a symposium held recently in Madrid under the auspices of UNESCO and the Spanish Government, specialists from 18 different countries examined some of the basic problems raised in this respect, particularly those concerning the relations between water and vegetation. The 42 papers read during the meeting showed the efforts being made by-- laboratories and institutes throughout the world which are devoting themselves to. the study of plants and their physiological reactions.

Seventy specialists reported on research now going on in this field —research which is so highly diversified that it involves such varied branches of science as physics, chemistry, ecology, geology, meteorology and biology. One of the participants, Professor Emberger, of the Botanical Institute of Montpellier, stated that the 10 working meetings at Madrid had enabled the scientists present to take an inventory of the main work being carried out in North and South America, Russia, Australia, Israel, India and Pakistan, and Spain. Obtaining such information from books and journals, he pointed out, “would have required four or five years.” Reports submitted by Spanish experts showed that in four-fifths of the territory of Spain the soil is affected by erosion and other phenomena characterising arid or semi-arid areas. Specialists taking part in the symposium were able to see this at first hand during a field-trip to the regions of Jaen, Granada, Almeria and Murcia. They were able to study soil conservation methods applied in the Guadiana and Guadalquivir valleys and to observe the damage wrought by extreme drought in the province of Almeria. They only had to look at the Mediterranean from the top of the cliffs to see huge ochre blotches in the sea: these blotches were lost land. Modern science considers land to be well-protected against erosion when no more than 12

tons of soil are lost each year per hectare (2.47 acres) —that is, an almost imperceptible layer only a few tenths of a millimetre in thickness. “In our country," said Mr J. Aguilo of the Spanish DirectorGeneral de Agriculture,” the effects of erosion are sp tragic that an average thickness of five millimetres (more than 3-16ths of an inch) is lost every year. If things go on at this rate, we will be farming rocks a hundred years from now." These problems of. erosion and aridity, of course, are not confined to Spain. The symposium brought out that 80 per cent, of the surface of Israel is arid and that countries such as Russia and the United States are not Completely immune from the ravages of drought over large stretches of their territory. “Water is lost through evaporation and infiltration,” said Pro fessor Victor Kovda, head of UNESCO’s Department of Natural Sciences. “It is only by controlling the transpiration and the photosynthesis of plants that we will be able to achieve really useful results in desert regions." In certain semi-arid areas, rainfall is rarer but intense. Water races down the mountainsides carrying away soil components and substances upon which plants feed. These torrents, which ruin the soil, must be stopped before they reach the hills and valleys below. This can only be done by planting appropriate vegetation which will catch the rain-water and, by reducing the flow down the mountainsides, will make it penetrate more effectively into the soil. Several papers presented to the Madrid symposium dealt with drought-resistant plants. Phytosociological maps of semi-arid regions were also produced. These involve a great deal of research: first, an inventory is taken of the natural vegetation in a given region, and then the plants are classified by species in order to determine which ones adapt themselves best to the area’s general geographical and climatological conditions. Such analyses have shown, for example, that in some parts of central and southern Tunisia, where the a aual rainfall never exceeds ten inches, it would be possible to replant olive trees on nearly 2,500,000 acres of land that is now lying fallow. Other questions such as the salinity of water and soils and hydroponics (soilless agriculture) were also discussed at the Madrid meeting. The Food and Agriculture Organisation—was represented at the symposium, serving as a reminder of some of the tremendous issues at stake: by the year 2000 there will be .probably nearly 5,500,000,000 mouths to feed.

The problem of the arid lands is a world problem and its solution requires international cooperation on a world-wide scale. This is the purpose of UNESCO’s major project on scientific research in the arid lands. (UNESCO.)