Dammed rivers: do or don’t?

At first glance, hydroelectric power from big dams appears to be a greener way to generate electricity than burning fossil fuels. But an organisation called "The World Commission on Dams" has concluded that dams' impact on eco-systems is "mostly negative" – results announced by no less than Nelson Mandela.

According to the commission, which is backed by the World Bank and industry:

Dam construction projects destroy habitat, reservoirs cover forest and farmland and downstream land is deprived of water and nutrients.

Moreover, rotting vegetation trapped in reservoirs emits methane and carbon dioxide.

Some estimates put the contribution of gases emitted by man-made reservoirs at more than one-quarter of the world's "global-warming potential."

And although dams make valuable economic contributions, projects have been undertaken for purposes of national pride – rather than electrical demand – and thus some have proved unprofitable, slow to deliver energy or water, and prone to corruption.

The commission estimates that the world has 45,000 large dams, with nearly half the world's rivers having at least one.

One-third of countries depend on hydropower for over half their electricity.

Over one-third of the world's irrigated land depends on dams.

The cheap irrigation water subsidises much of the world's food.

Some 80 million people have been displaced by dams, mostly through government force, and over $2 trillion has been invested in them.

That leaves experts to theorise that it might have been better to create electricity by burning gas, oil or even coal.

Source: A Barrage of Criticism, Economist, November 18, 2000.

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