minimal environmental impact

Publishing in the journal Nature, a group of 29 scientists have established a comparative scale for rating the immediate threat posed by nine environmental hazards--everything from climate change to ocean acidification. And while our warming climate gets most of the attention, more immediate problems may be brewing in our intensifying lack of biodiversity and out-of-whack nitrogen cycle.

The u.s. has some 2,100 terawatt-hours of near-shore wave power, about one eighth of which could be developed with minimal environmental impact, according to a recent marine-energy study for the electric industry. That amount of usable energy is equivalent to the output of all our existing hydroelectric dams.