Planetary Boundaries

The boundaries that should not be crossed for us to keep the Earth in its currently desirable state (Holocene)

Some of these boundaries show evidence of planetary scale tipping points and some do not. Those that don’t show evidence of tipping points, however, are helpful in regulating and preventing tipping points of other boundaries.

There are strong interactions among the different boundaries. Transgressing one boundary may cause cascading effects on others

CORE BOUNDARIES

Operate and regulate the entire Earth system, and they are the endpoint depending upon how the other boundaries operate.

1. climate change (TRANSGRESSED)
   • Climate can get into glacial or extremely hot periods
   • Control variable: GHG Concentration
2. Biodiversity loss (TRANSGRESSED)
   • Biodiversity is key to regulating the Earth’s functions and provision of Ecosystem Services
     • Pollinating bees and agriculture
     • Plant carbon sequestration
3. Chemical Pollution -Novel Substances-
4. Ocean acidification
   • Ocean can be in an oxygen rich state or oxygen free
5. Ozone Depletion
   • Necessary to protect biosphere from harmful radiations
6. [[ Land Use Change ]]
   • 40% of land is used for agriculture and urban areas
     • Affect biodiversity and ecosystem services provision
7. Biogeochemical loading: Global Nitrogen and Phosphorus Cycle
8. Global freshwater use
   • 25% of large rivers no longer reach the ocean because we’re taking out so much water
     • More water will be needed to feed a growing population
     • All biodiversity depends on water
9. Aerosol Loading

How Are Boundaries Measured?

• For each boundary we identify one or more control variable (e.g. GHG concentration)
• Then we look at what science says is the range of safety for that variable
• At which level will the variable cause a regime shift or start affecting other boundaries?
  • There’s high uncertainty on those
  • The lowest bound of the range is considered (for precaution)

Boundaries Co-evolution

• Planetary boundaries co-evolve with Humans and technology
  • The ozone depletion boundary co-evolved from humans’ emission of ozone-depleting substances

Resources:

• Course - Planetary Boundaries