2. Water pollution.

One of the most urgent environmental problems in the world today is the shortage of clean water. Table 1 shows the causes of the water shortage.

Increase in water consumption	Pollution of water supplies	Decrease in water reserves
Population growth Increase in per capita consumption	Acid rains Industrial waste Sewage	Dams Irrigation schemes Intensive farming Deforestation

Table 1. Causes of the world water shortage.

Access to clean drinking water is a basic human right. But acid rain, industrial pollution and sewage dumping have made sources of water undrinkable. Water pollution from industry can occur intentionally, when factories discharge their effluents directly into rivers, lakes, seas and oceans, or unintentionally, when accidents cause leakage of toxic waste into the water supply.

The Mediterranean Sea, for instance, occupies 1% of the world's water surface. But it is the dumping-ground for 50% of all marine pollution. Sixteen countries border on the Mediterranean. Almost all of them regularly dump shiploads of industrial waste a few miles off shore. Sewage effluents pour into the sea only meters from popular bathing beaches.

Another pollutant of water is oil. Some of it comes from accidents like the oil spill in the Gulf of Mexico in 2010, some from deliberate washing of tanks at sea and some from industrial effluents. Oil coats the feathers of sea birds and the scales of fish. It also has a less visible toxic effect: it reduces the level of oxygen dissolved in the water. Without dissolved oxygen, the sea cannot support any life at all. As well as the fish and seagulls that we can see, oil kills millions of tiny plants and animals in the deeper layers of the ocean.

Another cause is thermal pollution. Industries which use water for cooling (such as nuclear power stations) increase the temperature of nearby rivers and lakes by 5-10 degrees. Thermal pollution kills some animals and plants outright.

3. Soil destruction.

The earth is losing 24 billion metric tons of topsoil every year through intensive farming methods and deforestation. The end stage of this loss of topsoil is desertification, where all the organic and mineral content of the soil has disappeared, leaving only poor quality subsoil, which cannot support plant growth. About 20 million hectares of productive land become barren every year because of soil erosion. 30% of the world's land surface is threatened with desertification. Another hazard is salinization, which is caused by perennial irrigation (that is, irrigation year after year without a break) in dry climates.

The quality of soil can be improved by adding fertilizers and pesticides. But they cause environmental damage. These chemicals kill insects and other pests but they are poisonous to many other living things as well – including man. They are absorbed by the crops and often become concentrated in the food. Some of them accumulate in the human body and cause cancer or even birth defects.

Intensive farming techniques increase crop yield in the short term but deplete the quality of the soil in the long term, particularly in tropical regions. At best, crop yields fall and at worst, the soil becomes ecologically bankrupt and unable to sustain crops at all. Intensive farming is yet another example of the “live now, pay later” philosophy that may ultimately cost us the earth.

Soil pollution also occurs when industrial waste is buried or dumped on the land, and via polluted air and water. Industrial effluents include carbon, grease and other petroleum products, iron, mercury, dioxin and others.