Managing soil and water

Although humans have a long and distinguished history of economic and technological development, alongside this has been a general lack of consideration of the environment. Some worthy technological developments have been made at the expense of the environment, and damage to soils and water quality. For many centuries humans have practiced irrigation in the dryland areas of the world to turn drylands into fertile lands but much of this has been accompanied by increasing salinisation of the soils. Water brought into the dryland areas via rivers and channels or pumped up from the groundwater levels contains salts which as it evaporates leaves behind salts. Where this is an annual process the salts accumulate in the soil and eventually the soils become so saline that crops are unable to grow in them.

This salinisation of soils is believed to be one of the principal causes of the fall of some of the great empires. Salinisation now affects some one billion hectares of land in the dryland areas of the world such as in western United States, China, the Middle East, India and Pakistan. Here large regions are now either completely unable to support crops or at best only a very limited range of crops. It is of great concern to many observers that this problem gets steadily worse. It is an important example of damage to soil and water resources.There are numerous cases worldwide in which pollution in one form of another has affected soils, and has been passed from the soil into the various water systems, causing pollution of the water and damaging ecosystems. In the attempt to increase the yields of crops post World War II, farmers in the developed world used greatly increased quantities of fertiliser. While having the desired effect on crop yield which as much as trebled, there were some severe side effects.

Often less than half the fertiliser applied was used by the crops and much of the remainder was washed out of the soil into the river courses and underground water supplies. Here it caused pollution of rivers and streams, leading to algal blooms, deoxygenation of water courses, loss of aquatic life and damage to the ecosystems. It is a problem that has been recognised by many countries and steps are being taken in some countries to prevent continuation of this problem.There are some important situations in which soil and water have a particularly close relationship in the landscape, for example, in floodplains of rivers, coastal marshes, wetlands, in fact most low lying areas. With the need to grow more food for the growing population these areas have come under scrutiny for extending crop production and already many are now being put to such use. Examples of this include the draining of the fenlands to turn them into high quality, high yielding soils. This greatly alters the land use and the water balance in the landscape and precludes the use of the normally wet land for much wildlife and moisture loving flora. As humans continue to exploit the soil it is often at the expense of precious ecosystems.