The human environment
For most people in the developed world, the degradation of the human environment is at east a passing concern. But more often than not public attention is devoted to emotion-laden areas like disappearing species and population growth.

In the Third World ecological catastrophe means little to the mass of the poor concerned with day-today survival. Yet their poverty is probably the greatest threat to the environment. In their relentless search for food, fuel and land they often disrupt the ecological balance and jeopardize the natural world they depend on to survive.

Here we outline some of the world's major environmental issues and assess their impact on the people and the planet.

Carbon dioxide (CO₂) is released into the air by burning fossil fuels like coal, oil and wood. Clearing forest and brush also adds to the CO₂ build up. CO₂ allows the sun's heat to reach the earth but inhibits heat loss back into space. Scientists agree this 'Greenhouse effect' will increase the earth's temperature and may result in significant climatic changes.

Burning fossil fuels has released 140 billion tonnes of carbon into the atmosphere since 1850. Current fossil fuel consumption dumps 4.5 billion tonnes of carbon into the sky every year. The US, USSR and Europe have accounted for about 75 per cent of all CO₂ released to date.

Access to clean, safe water and sanitary facilities is perhaps the world's most pressing environmental issue. Over 25 per cent of the Third World's urban population and 71 per cent of the Third World's urban population lack access to clean water. Forty-seven per cent of urban and 87 per cent of rural Third World residents lack decent human waste disposal facilities.

It is estimated that drinking water and sewage systems could halve the incidence of diseases like typhoid, dysentry, cholera and schistosomiasis.

About 19 per cent of the earth's surface - 20 million sq km - and 80 million people are under direct threat of desertification - the destruction of once arable land by:

• over cultivation
• overgrazing and
• Improper irrigation

60,000 sq km of land are lost yearly - 650,000 sq km of productive land has been lost in the Southern Sahara over the last 50 years. In the Sudan the desert advanced by 100km from 1958 to 1975.

The world's most moist tropical rainforests are being cleared at the rate of 14 hectares per minute or 7.3 million hectares a year - mainly for agriculture and logging. As a result fragile tropical soils are being turned into wastelands, many tribal peoples are being decimated and thousands of unique plant and animal species are being destroyed.

Most trees are lost to agriculture rather than timber cutting. Peasants are forced to clear new farmland because available land is owned by large land-owners who grow crops for export. So forests act as safety valves for governments and the rich who wish to avoid land reform.

• 75% of all Central American forests have been destroyed since 1975 to produce beef for export to the US. Over the same period beef consumtion in Guatemala fell by half.

• In Java 85% of the population is landless. A government policy to move 500,000 people to other heavily forested Indonesian islands is well under way.

Industry continues to flood the world with up to 1,000 new chemicals a year - many of them untested. Only about 13 per cent of the 55,000 chemicals in commercial use have been tested for cancer in animals.

* In 1950, world production of organic chemicals was 7 million tonnes. By 1985 it is expected to rise to 250 million tonnes.

Industries in the West are slowly responding to public pressure to clean up. Large particle emissions have generally been reduced, although fine particle emissions continue to rise. However, there is a tendency for hazardous industries to move to Third World countries where pollution standards are less strict and governments desperate for jobs at any cost.

According to a 1975 study US corporations spend 50 per cent less on pollution control in the Third World than at home.