Contents - Previous - Next

The need for land evaluation

The nature of land

'Traditional systems of resource management and land husbandry are rapidly being abandoned; soil and environmental degradation are proceeding rapidly over large areas of the world. An alternative approach is essential.'

When populations were far smaller than today most societies were able to live in balance with their natural environment. As numbers expanded, man had a greater impact on the land through clearance for farming and in order to obtain fuel and construction material.

In most places this was a gradual process, and social groups were able to develop often complex systems for exploiting natural resources on a sustainable basis.

More recently, human populations have increased very rapidly, especially in developing countries, and demand for food and fuel has grown alarmingly. At the same time, changing economic and social conditions have undermined or destroyed traditional systems of land resource management.

Thus, not only is the land being cropped and grazed more intensively, with rest or fallow periods being drastically reduced or eliminated, but effective systems for maintaining fertility are no longer being applied. The result has been massive soil degradation on a world scale, through loss of plant nutrients and organic matter, erosion, buildup of salinity, and damage to soil structure.

Increasing demand for food, plus the fact that parts of the land most suited to crop production have been damaged or destroyed, has led to the expansion of cultivation and grazing into areas less suited to such uses, and ecologically more fragile. This has upset or destroyed natural ecosystems and modified or eliminated natural populations of flora and fauna.

Terraced rice fields

Land such as these terraced rice fields in Indonesia (left) is under intense pressure from the expansion of the human population. If land is not to be destroyed by these pressures, land evaluation studies must be carried out to ensure that maximum productivity is achieved, and can be sustained far into the future.

Much of the damage is irreversible, as when fertile topsoil has been stripped off to expose infertile subsoil or bare rock, or where plant or animal species have been wiped out. In other cases the damage can be economically irreversible, such as when millions of hectares become infertile due to the build-up of salinity.

There is an urgent need for a new approach. Traditional systems must be preserved and strengthened wherever possible, but it is clear that they alone are far from sufficient in view of the magnitude of the problem and the rate of destruction of the world's land resources.

How people or nations use their land depends on complex, interrelated factors which include the characteristics of the land itself, economic factors, social, legal, and political constraints, and the needs and objectives of the land users. In order to make rational decisions it is necessary to:

• collect the right information about the physical, social, and economic aspects of the land area in question; and

• asses the land's relative suitability for different uses in the light of the needs and objectives of the land user and the community.

This process is known technically as land suitability evaluation, or simply as land evaluation, and the basic methodology was set out in the 1976 FAO publication A Framework For Land Evaluation (Soil Bulletin 32).

Land evaluation is part of the process of land-use planning.

Food for the future

In 1982, the FAO study Land Resources for Populations of the Future concluded that, of 117 developing countries examined, no less than 64 would be unable to meet the food needs of their expanded populations in the year 2000 without the use of fertilizers, pesticides, improved seeds or improved conservation measures. In fact, of course, some agricultural inputs are being used in all these countries but large quantities of food still have to be imported.

The same study showed that if a modest increase in the level of agricultural inputs was projected, the situation improved significantly, with 28 of the 64 critical countries achieving self-sufficiency. At an optimistically high level of inputs, equivalent to that of Western Europe, a further 17 highly populated or exceptionally dry countries could become self-sufficient.

Decisions about land use need to be made at national level, provincial or district level, and at the level of the plot or farm. The basic process is the same, but the level of detail and map scale are quite different.

Successful land evaluation is necessarily a multi-disciplinary process and therefore the use of a standardized framework is essential to ensure logical, and, as far as possible, quantitative analysis of the suitability of the land for a wide range of possible land uses.

The nature of land

In the context of land evaluation, land is much more than the solid surface of the Earth. It includes the soils and rocks beneath, the atmosphere with its climates, the cyclic interchange of water between the sky, the ground, the rivers and the sea, and the whole mantle of living things, both plant and animal.

All of this is subject to the aims, abilities and stupidities of the human population. And a single change in any aspect of the land can precipitate a change in many others. Understanding the complexity of land, and the snowball effects of interacting changes that occur when balances are altered by development or disturbed by changing circumstances such as population growth, is essential to successful land evaluation.

It is impossible to foresee all the changes that may result from a single action. The art of land evaluation is to predict the most important changes, to decide whether these are desirable or acceptable, and thus to categorize the proposed action as a wise or an unwise use of land.

Contents - Previous - Next