Tampering With Wetlands, Rivers Costly

To redress these losses, the Washington-based research group is urging policy-makers to take account of the long-term damages caused by large dams and irrigation projects before launching new ones.

It is also asking that national and international authorities adopt integrated ecosystem-based planning at the local, national and international levels, instead of persisting in a fragmented and piecemeal approach to water and resource management.

"Both the concept of sustainability and the nature of ecosystems require that decisions affecting them look not only beyond the next few years but beyond the next few decades as well," writes the study's principal author, Janet Abramovitz.

In the last several years, advocates of big dams and related projects have suffered a number of setbacks, including the environmental destruction of the Aral Sea, the huge losses caused by the flooding of the Mississippi and Missouri rivers in 1993 and of the Rhine River in 1995, and the World Bank's withdrawal from a major dam project in the Narmada River Valley in India.

Nonetheless, major freshwater engineering projects, including the mammoth Three Gorges Dam project in China, the planned dam system for the Mekong River in Southeast Asia, and the proposed giant Hidrovia project of the Southern Cone of Latin America, are still proceeding. The new study suggests they and similar projects should be reassessed.

Abramovitz notes, for example, that, flood control improvements for the Mississippi river system, costing billions of dollars, actually increased both the frequency and severity of flooding, even while they crippled the river's ability to support native fauna and flora.

Indeed, among the greatest damages caused by such projects is a dramatic and irreplaceable loss of biodiversity in freshwater systems, according to the study. In most cases, that loss was caused by structures such as dams and reservoirs, but the introduction of alien fish, such as the Nile perch in Lake Victoria, has also had devastating results.

"Freshwater ecosystems are both disproportionately rich and disproportionately imperiled" by large dams, irrigation systems and widespread log the report says.

"As alarming as these numbers are, the rate of extinction is even more alarming -- a hundred to a thousand times the natural rate," says Abramovitz. The rate of freshwater species extinction far exceeds that of mammals and birds.

The study stresses that aside from their benefits for agriculture and industry, intact freshwater ecosystems are essential for human health and economies around the world.

The problem lies with policy-makers who do not take into account the long-term value of these benefits, Abramovitz argues. Instead, they are often dazzled by the promised short-term economic return of "mega-projects" which, in the long run, may prove much more costly.

Thus, one study cited by Worldwatch calculates the value of water in one Nigerian flood plain at $45 per 1,000 cubic meters if it is left alone to support local fisheries, farming and livestock. But, if that same water is diverted for other uses, its value drops to just 4 cents per 1,000 cubic meters.

Similarly, one 200,000 hectare swamp in Florida provides $25 million a year in water storage and aquifer replenishment, with no upkeep costs, according to the report.

And the value of intact mangrove swamps in Malaysia for flood control and storm protection alone has been estimated by economists at 4300,000 per kilometer, roughly the cost of rock walls that would be needed to replace them if they were cut down. If the value to fisheries of the swamps were included in the estimate, the total figure would be much higher.

The Worldwatch study calls for new approaches to freshwater management to redress the situation.

The most effective solution is to abandon the fragmented approach to managing rivers and their watersheds whereby dozens of agencies manage different parts or functions of a river system, according to Abramovitz.

Resources instead need to be managed in an integrated way over large enough areas and long enough time lines to allow species and natural ecological processes to remain intact.

To rehabilitate those systems which have already been heavily damaged by human intervention, the best and least costly way will be to reduce pollution, improve the flow of water and "encourage nature's own regenerative processes," Worldwatch says. "Once human pressures and stressed are removed, and natural processes are supported...a system can often achieve a self-sustaining state."

The study also urges greater participation in the planning and design of projects by local residents and non-governmental groups.