Lecture 2

• Quadruple Squeeze: simultaneous pressures on the Earth System

  • Population growth
  • Climate change
  • Ecosystem decline
  • Surprise
• Population growth:

  • "20/80 dilemma" - 20% of the world's population are responsible for most acceleration of environmental pressures, yet 80% are those most vulnerable to the impacts
• Climate change:

  • affects all biophysical systems
  • 550/450/350 dilemma - we want no more than 450ppm but are headed for 550ppm and higher
• Ecosystem decline:

  • healthy ecosystems vital in functioning and provide important services
  • 60% loss dilemma - over 60% of ecosystem functions have declined over the last 70 years
• Surprise/Uncertainty:

  • changes to climate system and ecosystems occur abruptly, irreversibly and are hard to predict
  • 99/1 dilemma - 99% of the changes tend to result form 1% of events
• Tipping point: the potential extreme dangers that exist beyond the current challenges faced by the earths ecosystems - which could alter its state - may be irreversible

  • Thresholds beyond which they cannot recover
• Resilience: the ability of a system to maintain key functions and processes in the faces of stresses or pressures - resists then adapts to change
• Resilient systems: adaptable, flexible and able to cope with change and uncertainty
• Planetary Boundaries: 9 processes that regulate the stability and resilience of the Earth system

  • quantitative - within which humanity can continue to develop and thrive
  • crossing these boundaries - increases risk of large-scale abrupt of irreversible environmental changes
• Examining the Planetary Boundaries Chart:

  • Green: process is within the safe operating space - boundary has not been crossed
  • Orange: boundary has been crossed - the bigger the wedge the higher risk of destabilising the earth system
  • Grey: process is not yet quantified - not sure how to measure it although it is important
• A planetary boundary is placed well before reaching the threshold of an earth-system process
• 9 planetary boundaries:

  • Freshwater change - green water (orange), freshwater (grey)
  • Stratospheric ozone depletion - grey
  • Atmospheric Aerosol Loading - grey
  • Ocean acidification - grey
  • Biochemical flows - orange
  • Novel entities - orange
  • Land-system change - orange
  • Biosphere integrity - grey and orange
  • Climate change - orange