ECOLOGY: The Other H's.

Fisheries scientists have long identified the factors implicated in salmon decline as the "four H's": hydropower dams, harvesting, habitat degradation, and hatchery misuse. According to a new plan by nine federal agencies, known as the "All-H Paper," improvements in the other three H's will provide benefits that are more certain and widespread than those from dam breaching. But addressing the other H's may be even more costly than breaching dams.