2025: The year mankind hits the point of no return?

The most important news of 2012 won't be the Wisconsin recall, the European financial meltdown, or the possibility of Iranian nukes, says James Fallows at The Atlantic. It'll concern a sprawling new report in the journal Nature, which claims that Earth may very soon hit a tipping point that could trigger huge, disastrous planetary changes — bad news for Earth's occupants. Here's what you should know:

What does the paper say?

The argument goes that humans have already converted roughly 43 percent of the planet's usable land area into farms, livestock ranches, and cities. As many studies have already suggested, when more than 50 percent of our natural landscape is lost, the ecological web that sustains humanity will collapse beyond repair. The new study suggests that this "tipping point" will be "marked by extinctions and unpredictable changes on a scale not seen since the glaciers retreated 12,000 years ago," says Stephanie Pappas at LiveScience. Under "business-as-usual conditions," this could take place as soon as 2025.

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How did the researchers reach this conclusion?

By sorting through piles and piles of data. The findings all point to the same conclusion: If humans continue to use up resources at the current rate, "there will be a reduction in biodiversity and severe impacts on much of what we depend on to sustain our quality of life, including, for example, fisheries, agriculture, forest productions, and clean water," says Anthony Barnosky, a professor of integrative biology at UC Berkeley and the lead author of the paper. At that point "it really will be a new world, biologically."

Can we take action to stop this?

Maybe not. A team of 22 scientists from the Berkeley Initiative in Global Change Biology assembled the study in preparation for the Rio+20 global sustainability summit this week in Rio de Janeiro. Expectations for the gathering are low, but many environmental groups are "pushing for action," says Justin Gillis at The New York Times. But at the original meeting 20 years ago, world leaders failed to meet "even a fraction of the promises" avowed, such as reducing global emission rates, which have since skyrocketed.

Is something catastrophic really going to happen?

The authors provide clear examples of large-scale ecological disasters that have already affected society, says Gillis, like the collapse of cod fisheries in the North Atlantic, outbreaks of invasive species, and extinctions penetrating the far corners of the globe. However, many scientists think that the event can be avoided, and the "ecological limits to human population and economic growth" can be solved through human innovation (though it isn't clear exactly what that would be). Says Barnosky: "Looking into the past tells us unequivocally that, yes, it can really happen. It has happened. The last glacial/interglacial transition 11,700 years ago was an example of that."

Sources: The Atlantic, LiveScience, New York Times, Rolling Stone