Climate Change
Climate Change
Stabilizing greenhouse gas concentrations to avoid global warming beyond safe levels.
Example: Atmospheric CO₂ exceeding 350 ppm indicates boundary transgression.
Biosphere Integrity
Biosphere Integrity
Preserving biodiversity and ecosystem functionality across the planet.
Example: Extinction rates more than 10× natural background levels.
Land-System Change
Land-System Change
Maintaining forest and ecosystem cover to support resilience and climate regulation.
Example: Global forest cover falling below 75% of original extent.
Freshwater Use
Freshwater Use
Ensuring sustainable withdrawal of surface and groundwater.
Example: Planetary boundary set at 4000 km³/year of consumptive use.
Biogeochemical Flows
Biogeochemical Flows
Controlling nitrogen and phosphorus cycles to avoid eutrophication and dead zones.
Example: Over 60% of applied nitrogen escapes into the environment.
Ocean Acidification
Ocean Acidification
Maintaining pH levels to protect marine ecosystems and carbonate chemistry.
Example: Aragonite saturation falling below 80% of pre-industrial levels.
Atmospheric Aerosol Loading
Aerosol Loading
Controlling particulate matter concentrations that affect climate and health.
Example: High black carbon levels disrupting monsoon systems.
Novel Entities
Novel Entities
Limiting introduction of new synthetic compounds with persistent ecological effects.
Example: PFAS, microplastics, and endocrine disruptors exceeding safe limits.
Stratospheric Ozone Depletion
Ozone Depletion
Preventing loss of ozone layer critical to shielding Earth from UV radiation.
Example: Antarctic ozone hole and CFC-induced ozone layer thinning.