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... Looking at necessities of a livable Earth -- including the climate, freshwater systems, biodiversity and soil nutrients -- the researchers find almost all have crossed crucial thresholds. The only global system yet to breach safe limits is aerosols, even as small-particle air pollution contributes to 8 million deaths a year.

The new paper updates a scientific project that began in 2009 to assess "planetary boundaries" (since renamed "Earth-system boundaries") and how transgressing them will pose risks to human society and nature around the world.

Researchers assessed each of these systems on two factors. One was safety, or how long until the system may no longer perform in the way people have relied on it to. The other was justice, or "the risk of significant harm" to people alive today and those not yet born.

They conclude that to avoid further destabilization, countries should keep at least half of the planet's ecosystems intact, limit groundwater extraction and set hard limits on use of nitrogen and phosphorus fertilizers.

The new work offers a way for countries, businesses and cities to begin to define their own responsibilities, based on efforts such as the Science Based Targets initiative, which helps companies set climate goals, and the Task Force on Climate-Related Financial Disclosures, which set down guidelines for assessing climate risk and communicating it to shareholders and others. ...