In simple terms
The ocean absorbs CO₂. This slows atmospheric warming, but changes seawater chemistry and reduces carbonate available to shell-building organisms.
Why it matters
Corals, shellfish and many plankton depend on carbonate chemistry. Their decline can affect reefs, food webs, fisheries and the ocean’s wider role in the Earth system.
What puts pressure on it?
- Fossil-fuel CO₂ emissions
- Land-use emissions
- Regional nutrient and ecosystem pressures that can amplify local effects
How scientists track it
- Surface-ocean aragonite saturation state
What helps
- Cut fossil CO₂ emissions
- Protect marine ecosystems
- Reduce nutrient pollution reaching coasts
Planetary Boundaries are global guardrails. They are not personal quotas, and individual actions alone cannot restore them. Policy, infrastructure, business and collective change matter alongside household choices.