Those in peril in the sea

have been altering habitats—sometimes deliberately and sometimes accidentally—at least since the end of the last Ice Age. Now, though, that change is happening on a grand scale. The plough and the chainsaw bear much of the blame, but is a growing factor, too. Fortunately, the human ingenuity that is destroying nature can also be brought to bear on trying to save it. Some interventions to save ecosystems are mind-boggling long-shots. Consider a scheme to reintroduce, by Asian elephants, something resembling a mammoth to Siberia. Their feeding habits could restore the grassland habitat that was around before mammoths were exterminated, increasing the sunlight reflected into space and helping keep carbon compounds trapped in the soil. But other projects have a bigger chance of making an impact quickly. As we report, one example involves .