Water— the Issue of This Century
The world is running short of fresh water．Populations are growing bigger and thirstier(渴的), with the result that fresh water is becoming increasingly scarce(缺乏)．Half the world's wetlands have disappeared during the last century, while estimates suggest that water use will rise by 50% in the next 30 years.
The World Bank report estimates that as much as half of the world's population, concentrated in Africa, the Middle East and south Asia, will face 'severe water shortages' by 2025．Local water conflicts and the loss of freshwater ecosystems appear large in some regions.
A similar picture emerges from the globe's salt water regions．Three-quarters of the world's people may live within 100 km．of the sea in 2025, putting even more pressure on stretched coastal ecosystems．Two thirds of fisheries(渔业) are exploited at or beyond their sustainable limits, and half the world's coral reefs(珊瑚礁) may perish in 100 years．Almost 60% of coral reefs and 34% of fish species are at risk from human activities, the Bank says.
The report concludes that there is ample evidence to justify immediate and coordinated action to safeguard supplies and use water more efficiently.
Fresh water consumption is rising quickly, and the availability of water in some regions is likely to become one of the most pressing issues of the 21st century.
A third of the world's population—around two billion people—live in countries that are experiencing moderate to high water shortages．That proportion could (at current population forecasts) rise to half or more in the next 30 years unless institutions(制度) change to ensure better conservation and allocation of water.
China is one country where the portents(征兆) are gloomy．The most water-stressed country in East Asia, China is exploiting 44% of its usable water, a figure projected to rise to 60% by 2020．Primary withdrawal of water of more than 60% is widely considered by water experts to exceed the environmental carrying capacity of a river basin system．Although China's total use appears still to be reasonable, it has several basins that are severely stressed environmentally.
Withdrawals exceed environmental limits in Afghanistan and Pakistan, and will exceed them in India by 2020．In the Middle East and North Africa, only Morocco has unexploited water resources．The rest have exceeded environmental limits and many are mining aquifers(蓄水层)—bodies of water-bearing rock—the report says.
It is estimated that water use will rise by 50% in the next 30 years.