Magazine article Geographical

Damned If You Do ... on All of the World's Great Rivers, from the Amazon to the Zambezi and the Nile to the Mekong, Large Dams Are Being Planned to Help Cope with Climate Change and Promote Development. but Will Their Construction Inevitably Come with Social and Environmental Costs

Magazine article Geographical

Damned If You Do ... on All of the World's Great Rivers, from the Amazon to the Zambezi and the Nile to the Mekong, Large Dams Are Being Planned to Help Cope with Climate Change and Promote Development. but Will Their Construction Inevitably Come with Social and Environmental Costs

Article excerpt

A large dam, rising 200 metres and holding back several billion cubic metres of water, can be an undeniably breathtaking spectacle. But while they often feature on lists of the modern engineering wonders of the world, the impact of dams is often far more than visual. Large dams are now found on every continent--and on 60 per cent of the world's rivers--and environmentalists continue to question whether their benefits are outweighed by the repercussions they cause downstream.

In many countries, large dams are important contributors to development, About half of the world's large dams were built primarily for irrigation and many powered the Green Revolution of the 196Os and '7Os. They're estimated to contribute directly to 12-16 per cent of global food production, and account for 40 per cent of irrigation. They also provide at least 19 per cent of the world's electricity, according to the World Bank.

A large dam, according to the logically named International Commission on Large Dams, is defined as more than 15 metres high. Worldwide, their number stood at 5,000 in 1950, three quarters of them in North America, Europe and other industrialised regions. By 2000. there were 45,000 across 140 countries. After a brief hiatus, construction has picked up again, and according to International Rivers, there are now more than 54,000 large dams.

Their impacts are far reaching. 'It's strange to think that a dam can cause problems 2,000 kilometres away in a river delta, but it's true,' says Dr Jian-hua Meng, WWF's sustainable hydropower specialist.

Rivers and lakes are more fragmented and degraded than any other ecosystem, according to Diversitas, an international group of biodiversity experts, with extinction rates for freshwater species of animals such as fish, frogs, crocodiles and turtles 'four to six times higher than their terrestrial and marine cousins'.

DEVASTATING IMPACT

The impact of large dams on poor and rural communities has also often been devastating. 'Environmental and social issues are the big Achilles heels for dams,' says Aviva Imhof campaigns director for International Rivers. 'In the past, the experience of the impact of dam building globally has been very poor.'

Many dams are in remote areas whose people have a distinct social and cultural identity that not only separates them from energy-seeking urban centres, but exposes them to disadvantage by development. By the mid-2000s--when the most recent figures were produced--between 40 million and 80 million people had been displaced from their homes by dam construction. Since then, Imhof points out, a further 20 million Chinese and ten million Indians have been displaced.

Other studies suggest that the wider impact reaches extraordinary levels. The authors of Lost in Development's Shadow. The Downstream Human Consequences of Dams conservatively estimate that 472 million people have been directly affected by changes in river flows and ecosystems. Imhof believes that the true figure could be as high as 800 million.

'Construction is mature--the industry knows how to build dams, but the social side of this engineering is more tricky,' says Meng. 'We can't endorse the building of dams for the benefit of a few while others pay a high price in terms of loss of homes and income. It's about building the right dams in the right places. Done properly, hydropower can make a powerful contribution to energy-poor people and to carbon-free energy on a global scale. But if you leave a downstream river dry, or with a constant flow something that's unnatural--you don't have the river dynamics for keeping wetlands alive.'

TIPPING POINT

And some of the world's most iconic rivers are set to be affected. The Amazon has had a lot thrown at it but now, in addition to deforestation, it faces an onslaught of dam building. The Brazilian government has plans to build more than 60 large dams along the river and its tributaries over the next 20 years, and hundreds more are planned for the wider Amazon basin. …

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