fertilizer runoff

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.

Where: Coastal areas
Cost: $800 million per square mile of island

The Problem The wetlands are losing ground. Crops and condos are rapidly overtaking much of the waterlogged land-home to thousands of bird and animal species-while pollution and sea-level rises take care of the rest. With this loss comes drastically reduced water quality, increased flooding of surrounding areas and the looming specter of the extinction of many species.