From space, most of our planet is a deep, satisfying blue. Water, the essential ingredient for life, seems to be everywhere. But, as this issue highlights, the prospects at ground-level are not so agreeable. It is salutary to realize that in our issue of this very date 5 years ago, we wrote an Editorial that, with small amendments, we might well have simply reprinted this week (see Nature 422, 243; 2003).
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