"A number of scientists have warned in recent years that if we keep pushing the planet this way, we will cause sudden, irreversible damage to the systems that made human civilization possible in the first place. Typically, they've just focused on one of these tipping points at a time. But in today's issue of the journal Nature, Rockstrom and 27 of his fellow environmental scientists argue that we have to conceive of many tipping points at once. They propose that humans must keep the planet in what they call a "safe operating space," inside of which we can thrive. If we push past the boundaries of that space - by wiping out biodiversity, for example, or diverting too much of the world's freshwater - we risk catastrophe.
Unfortunately, the authors of the Nature paper maintain, we've already started pushing out beyond these boundaries without knowing where they actually are."
Three of the thresholds suggested by the paper have already been passed, and the other four will be soon, according to the authors.