Threats to soil quality

There are now many uses to which soils are put (See Soil Functions). Each of these uses depends on certain soil properties and what might suit. Requirements of soil for agriculture, for example, may not suit certain types of forestry or biodiversity. There are many examples in history of glaring mismatches between the use of a soil for a particular purpose and the ability of the soil to deliver adequately for that purpose, i.e. the use is not sustainable. This has led to many examples of catastrophic soil damage which clearly reflect the mismatch. There is a whole catalogue of damage to soil quality brought about partly by ignorance and partly by lack of interest or concern. This is why desertification is now affecting 70 per cent of the drylands of the world, up to 20 million hectares are affected by salinisation, and 6-7 million hectares of soils are being lost annually by soil erosion.

In addition to the huge losses of land by erosion, desertification and salinisation, there are also several other problems affecting the soils of the world which jeopardise their quality and ultimately their sustainability. The tremendous growth in industry in the last 250 years has left behind a legacy of pollution and contamination of soils. This includes large areas of contaminated land, much of which cannot now be decontaminated, which is now either derelict or so contaminated that it cannot be used for any useful purpose. While being mainly a product of the developed world there is much evidence now that rapidly developing countries such as India and China are also subject to significant contamination by industry, with the accompanying loss of much good land. Building on land also presents a major threat to soil quality because it 'seals' the ground usually in a way that prevents its use for any other purpose. Again there is a huge increase in urbanisation worldwide which leads to the sealing of significant areas of land.

One of the other lessons we have learned in the last 50 years is that intensification of agriculture to produce more crops can have undesirable side effects if not managed properly. Thus in Western Europe, for example, following World War II there was major intensification of agriculture. This involved more intensive use of fertiliser, more pesticides to kill unwanted pests, more intensive cultivation of land and increased planting of crops on steep slopes. The result of this has been damage, such as soil compaction and loss of organic matter, impacts on biodiversity and loss of highly fertile organic soils. Importantly, this has led to leaching of excess nutrients into streams and rivers where it seriously affects the aquatic systems. The problems here are now recognised and steps have been taken in many countries to reduce the problem. It shows, however, that as we need to use soils more and more intensively so we need to know about their qualities and resilience if we are not to seriously damage them and the environment.