THE BOUNDARIES SAFE • Extinction rate — Extinctions for every 1 million species INCREASING RISK HIGH RISK Boundary for global average 1 extinction 100 to 1,000 Current assessment • Nitrogen — In megatons per year 62 Mt 150 Mt • Phosphorus — In megatons per year; flow from freshwater into ocean 11 Mt 22 Mt Forest cover — In percent coverage of original cover; global average Biogeochemical flows  Biosphere integrity Less than 75% 62% Climate change — Atmospheric carbon dioxide, in parts per million 350 ppm 396.5 ppm Ocean acidification — Seawater carbonate ion concentration compared with pre-industrial levels Less than 80% 84% Stratospheric ozone — Concentration compared with pre-industrial levels Less than 95% A problem in Antarctica in the spring (at 69%) but improving Freshwater use — In cubic kilometers used every year 4,000 km3 2,600 km3 • Biodiversity abundance — A measure of ecosystem degradation Not yet quantified Atmospheric aerosols — Can have serious human health impacts Not yet quantified Novel entities — New substances, modified life forms Not yet quantified KEY

SOURCE: Science.