According to researchers who gathered here at a high-powered summit this month, toxicology may be on the verge of changing the way it collects raw data--adopting a process that could reduce animal use and improve test results. The new approach, called "toxicogenomics," uses DNA arrays to profile gene expression in cells exposed to test compounds. But some leaders in the field warn against rushing too quickly to embrace DNA tests, which are still difficult to interpret.
J ust outside the small town of Stabler in Washington, hydrologist Bengt Coffin surveys a mountain river that he helped to revive from a decades-long coma. Today, the clear waters of Trout Creek run fast and cool between banks covered in young alder trees. But just five years ago, an 8-metre-high concrete wall blocked the river at this site. The dam and the reservoir behind it had tamed the river and made it difficult for endangered steelhead trout (Oncorhynchus mykiss) to reach their spawning grounds upstream. In 2009, Coffin led the US Forest Service effort to remove the dam, and Trout Creek has since regained the look of a young river. Vegetation has covered the scars left by the dam and reservoir, and steelhead and other species have started to rebound. The revival of Trout Creek is part of a growing trend in the United States. About half of the nation's roughly 85,000 known dams no longer serve their intended purposes, and an increasing number are being removed. Around 1,150 have gone so far, mostly in the past 20 years, according to a tabulation by the watchdog group American Rivers in Washington DC. In an era when many countries are still building dams, the United States is taking them out. "It used to be a crazy idea. Now it's accepted, " says Amy Kober, director of communications for American Rivers. Most of the demolished structures were lower than 5 metres, but in the past few years, projects in the Pacific Northwest have removed much taller ones. At the top end of the spectrum, the US National Park Service is dismantling the 64-metrehigh Glines Canyon Dam, the largest of a pair of big dams on Washington's Elwha River. Many of the larger dams were removed because their operators decided that it was too costly to bring the old Rivers on the run As the United States destroys its old dams, species are streaming back into the unfettered rivers.
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