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GEO-3: GLOBAL ENVIRONMENT OUTLOOK  
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Environmental change

Two basic functions performed by the environment are the 'source' or production function that supports the livelihood of millions who depend upon environmental resources, and the 'sink' or pollution absorption and cleansing function essential for human health and well-being. Not only are these two functions closely connected in a cycle of production and renewal but they are being increasingly impaired and degraded by human impacts.

Watershed management and flooding

Poor land-use management can have profound effects on people. By 1986, deforestation in the upper reaches of the Yangtze basin in China had reduced forest cover from 22 per cent of total area in 1957 to only 10 per cent. As a result, soil erosion from the upper reaches and siltation in the middle and lower reaches had become intense. In 1998, the most severe flood in Chinese history hit the Yangtze valley, affecting 223 million people and causing more than US$36 billion in economic losses (Shougong 1999).

In July 1997, vast areas of southern Poland, the eastern Czech Republic and western Slovakia experienced one of the most disastrous floods in history when the Oder, Elbe, Vistula and Morava Rivers overflowed. In Poland alone, flooding affected one-quarter of the land area, including nearly 1 400 towns and villages, destroyed 50 000 homes and caused 162 000 people to be evacuated. Total damage was estimated at US$4 billion. The severity of the floods was attributed to the destruction of forest and wetlands, engineering works on the main rivers and tributaries, and the removal of water-retaining vegetation which made riverine areas more susceptible to flooding. Floods have become an increasingly regular occurrence for more than a decade (EEA 2001).

Degradation of natural resources such as land, fresh and marine waters, forests and biodiversity threatens the livelihood of many people but especially the poor. For example, water tables are falling fast under the North China plain. In 1997, almost 100 000 wells were abandoned apparently because they ran dry as the water table fell, but 221 900 new wells were drilled. The drilling of so many wells reflects a desperate quest for water (Brown 2001).

The 'sink' function of the environment operates through such processes as nutrient recycling, decomposition, and the natural purification and filtering of air and water. When these functions are impaired, health can be jeopardized by contaminated household water, sanitation problems, indoor air pollution, urban air pollution and agrochemical pollution.