Climate Change
The Nine Planetary Boundaries
In 2009, a team of Earth system scientists led by Johan Rockström identified nine processes that regulate the stability of the Earth system. Together they define a “safe operating space” for humanity — thresholds that, once crossed, risk triggering abrupt, irreversible environmental change.
Source: Stockholm Resilience Centre · Planetary Health Check 2025 · Richardson et al. (2023)
Carbon Dioxide (CO₂)
The concentration of carbon dioxide in the atmosphere has surpassed safe limits, driving unprecedented global warming and destabilising Earth's climate systems.
Biosphere Integrity
Species are going extinct at more than 100 times the natural background rate — the most dramatic loss of life since the dinosaurs disappeared 66 million years ago.
Land-System Change
Forests, wetlands and other natural ecosystems are being converted to farmland and urban areas faster than they can recover, disrupting carbon, water and nutrient cycles.
Freshwater Change
Human alteration of river flows, groundwater extraction, and disruption of soil moisture is destabilising the global freshwater cycle far beyond safe limits.
Biogeochemical Flows
Industrial fertiliser production has flooded ecosystems with reactive nitrogen and phosphorus, creating ocean dead zones and toxic algal blooms worldwide.
Ocean Acidification
The ocean has absorbed so much CO₂ that its chemistry is changing, becoming more acidic and threatening the survival of coral reefs, shellfish and marine food chains.
Novel Entities
Over 350,000 synthetic chemicals — plastics, pesticides, PFAS 'forever chemicals' and more — are being released into the environment faster than we can assess their safety.
Atmospheric Aerosol Loading
Airborne particles from burning fossil fuels and biomass affect climate, monsoon patterns and human health — but globally this boundary remains within safe limits.
Stratospheric Ozone Depletion
Thanks to the 1987 Montreal Protocol — the most successful environmental treaty in history — the ozone layer is recovering and this boundary remains within safe limits.
About the Planetary Boundaries Framework
The Planetary Boundaries framework was first published in 2009 by a group of 28 Earth system scientists led by Johan Rockström of the Stockholm Resilience Centre and Will Steffen of the Australian National University.
For the past 10,000 years — the Holocene epoch — Earth has remained in a remarkably stable environmental state. Human civilisation, agriculture, and technology all developed within this narrow window of stability. The framework identifies nine biophysical processes that maintain this stability and proposes quantitative limits for each.
As of the latest scientific assessment (2025), seven of the nine boundaries have been transgressed: climate change, biosphere integrity, land-system change, freshwater change, biogeochemical flows, ocean acidification, and novel entities. Only atmospheric aerosol loading and stratospheric ozone depletion remain within safe limits.
Crucially, these boundaries interact. Crossing one boundary increases the risk of crossing others. Climate change and biosphere integrity are considered the two “core boundaries” because they fundamentally influence the state of all other processes.
The ozone layer recovery — driven by the Montreal Protocol (1987) — provides a powerful precedent: when the world acts decisively with clear scientific evidence, we can pull back from the brink.
Key References
- Rockström et al. (2009). “A safe operating space for humanity.” Nature 461, 472–475.
- Steffen et al. (2015). “Planetary boundaries: Guiding human development on a changing planet.” Science 347(6223).
- Richardson et al. (2023). “Earth beyond six of nine planetary boundaries.” Science Advances 9(37).
- Sakschewski et al. (2025). Planetary Health Check 2025. Potsdam Institute for Climate Impact Research.