"Today the concept of global carrying capacity has evolved into the idea of planetary boundaries. The boundaries set the environmental terrain "within which we expect that humanity can operate safely," a team of twenty-nine European and American scientists argued in an influential report from 2009. (It was updated in 2015.) To prevent "non-linear, abrupt environmental change," they said, humankind must not transgress nine global limits. That is, people must not 1. use too much fresh water; 2. put too much nitrogen and phosphorus from fertilizer into the land; 3. overly deplete the protective ozone in the stratosphere; 4. change the acidity of the oceans too much; 5. use too much land for agriculture; 6. wipe out species too fast; 7. dump too many chemicals into ecosystems; 8. send too much soot into the air; and 9. put too much carbon dioxide into the atmosphere."