The environmental damage caused by mountaintop removal mining across Appalachia has been well documented. But scientists are now beginning to understand that the mining operations’ most lasting damage may be caused by the massive amounts of debris dumped into valley streams.

The Mekong has long flowed freely, supporting one of the world’s great inland fisheries. But China is now building a series of dams on the 2,800-mile river that will restrict its natural flow and threaten the sustenance of tens of millions of Southeast Asians.

Led by China, the developing world is engaged in a flurry of dam construction, touting hydropower as renewable energy in an era of global warming. But critics point out that the human and environmental costs of dams remain high.

Geologist Yong Yang has serious concerns about plans for a massive Yangtze River diversion project. When he went public with them, he found out how difficult it can be to challenge a government decision in China. The third in a series on Chinese environmentalists.

With the support of Gov. Sarah Palin, mining interests have defeated an Alaska ballot measure that could have blocked a huge proposed mining project. Now, plans are moving forward to exploit the massive gold and copper deposit at Bristol Bay, home of one of the world’s greatest salmon runs.