Earth has crossed key 'planetary boundaries', scientists warn.

Human activity threatens eight of the planet's critical life-support systems, and seven of them have already moved into the danger zone, according to a large-scale Earth science survey by more than 60 researchers published Wednesday in The Lancet Planetary Health .

Looking at the needs of a viable Earth—including climate, freshwater systems, biodiversity, and soil nutrients—researchers found that nearly all exceeded critical thresholds. Aerosols are the only global system that has not yet exceeded safe limits, even though small particle air pollution contributes to 8 million deaths annually. (Eric Roston, more at bloomberg.com)