Each wedge of this graph represents one of the nine proposed boundaries. The green zone covers what the scientists call a "safe operating space for humanity." The red zone shows whether the planet is in or out of bounds, and by how much. We have exceeded three boundaries -- extinction rates, nitrogen loading and global warming -- and the scientists note "significant uncertainty" about how long we can live in the red zone before the damage is irreparable.
"For the first time in human history, the human demand for the natural resources we are dependent upon is, for some critical resources, beginning to approach, in some cases exceed, their global supply," said Katherine Richardson, a boundaries co-author and professor of biological oceanography at the University of Copenhagen. The scientists' work continues to evolve, from re-analyzing the role of phosphorus pollution -- originally included in the nitrogen boundary -- to quantifying nature's life-support systems.
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