Lakes in need of restoration

Lakes are a source of food, commerce and energy for millions of people

CNN -- Most of the world's freshwater lakes and reservoirs, about five million of them, are facing serious ecological threats.

There are two major reasons: overuse, especially from diversion of lake water for irrigation; and contamination, by toxic waste and nutrients from industry, farms and sewage.

According to scientists, lakes are the most vulnerable of all natural ecological systems, and difficult to restore. But policy makers in many countries have widely ignored what is happening to their lakes.

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The amount of water stored in the world's freshwater lakes is about 35 times the amount in rivers.

At least one billion people depend directly on lakes for their livelihood and for drinking water. Lakes are a source of commerce, food and energy production, and a major habitat for plant and animal species.

Experts attending an international lake conference in Japan have called for new measures to protect and restore lakes, focusing on surrounding watersheds and the runoff carrying contaminants that slowly accumulate in lakes.

"You have to pay attention to these and stop them from accumulating because you won't see, if you're just looking at the lake, you don't see these signs until it's too late," William Cosgrove of the World Water Council.

After a lake becomes degraded, especially a large lake, it takes a long time and extensive capital investment to restore it.

That is why successful restorations are rare, especially in developing countries and why scientists say it is critically important to save the world's lakes, while there is still time.