|
Definition:
Modifications of soil features or, more generally, of its chemical and biological balance, caused by the discharge of polluting substances.
There are four sorts of polluted land:
Places where gas works, oil refineries, oil storage depots nuclear power stations and chemical factories have been built
Refuse dumps where domestic and industrial waste are deposited
Agricultural land where modern farming methods have been practised
The rest of the world?s land surface
The first might be regarded as the price we have to pay for what such places produce as long as the pollution stays where it is. Unfortunately movement of vehicles on to and off the land, run-off of rain water and dust carried by the wind spread the pollution further afield. There is also no way to prevent wildlife getting onto such land and picking up the injurious material directly.
The second is the result of wilful refusal to build in the cost of treating such waste to make it less harmful when calculating the prices of products and of refuse disposal.
The third is the result of the use or misuse of chemical ?aids? such as fertilisers, pesticides, herbicides and so on, coupled with the practice of monoculture which creates the illusion of their necessity.
Chemical fertilisers were introduced because of a shortage of organic ones as animal husbandry changed and declined. Applied with care, using the correct amounts to correct deficiencies that have been measured in the soil, they increase yields and do little harm. They are usually applied without prior checks to determine need, and usually in too large quantities despite the extra cost this involves.
The surplus leaches out into the drainage system (the nearest river) upsetting the balance of nutrients in the water and causing excessive growth of water plants such as blanket weed. Other plants are choked and the food chains of which they are parts wither away and die.
Insecticides have been used for many years. The old ones quickly degraded in the soil and did no harm. Their modern equivalents persist for many years, pass up the food chain to affect insectivorous fish, birds and mammals and the predators that feed on them, at the same time destroying many soil micro-organisms on which the natural fertility of the land depends.
They also drift well beyond the areas to which they are intended to be applied, often affecting land where domestic pets are exercised. The animals absorb the pesticides through the skin of their feet or ingest it when grooming themselves, an increasingly common cause of domestic pet ailments.
The fourth type of polluted land results from phenomena such as ?acid rain?. Quantities deposited at a time are very small, but because the materials are so persistent the effect is cumulative over many years. Often the effect is not visible for a long time, then there is a sudden decline in the health of the ecosystem and a near-desert results.
|
Quick Reply
