3.2H Loss of biosphere integrity (HL) Notes

1. Biosphere integrity is one of the nine planetary boundaries that define a "safe operating space" for humanity.
2. It measures the stability and resilience of Earth's ecosystems, including:
   1. Genetic diversity (variation within species)
   2. Functional diversity (variety of ecosystem roles performed by species)
   3. Species diversity (overall richness of species)
3. Scientists have determined that the loss of biosphere integrity is one of only two planetary boundaries already dangerously exceeded.
4. Species extinctions are occurring far beyond natural background rates, meaning Earth’s ecological balance is becoming increasingly unstable.

How Much Has the Boundary Been Exceeded?

1. The boundary for biosphere integrity has already been crossed.
2. Current extinction rates are 100 to 10,000 times higher than the natural background rate.
3. Natural extinction rate (background rate): ~1 species per 1 million species per year (Smithsonian estimate)
4. Current estimated extinction rate: Up to 10,000× higher than background
5. Human drivers include:
   1. Deforestation
   2. Overexploitation
   3. Pollution
   4. Climate change
   5. Habitat fragmentation
   6. Invasive species introduction

Consequences of Loss of Biosphere Integrity

1. Reduced Ecosystem Stability

1. Biodiverse ecosystems have functional redundancy, multiple species performing similar ecological roles.
2. When species are removed, redundancy declines, and ecosystems become more fragile.
3. A drop in key species can destabilise entire food webs, nutrient cycles, and biological interactions.

2. Loss of Critical Ecosystem Services

1. Declining biodiversity reduces:
   1. Pollination
   2. Soil fertility and nutrient cycling
   3. Water purification
   4. Carbon sequestration
   5. Disease regulation
2. When these services collapse, food security and human well-being are directly threatened.

What are Tipping Points?

1. A tipping point is a critical threshold beyond which a small change results in rapid, irreversible shifts to a new state.
2. Once passed, the system cannot return to its original state even if pressures are reduced.

1. Amazon Rainforest Dieback

1. Deforestation and warming reduce moisture recycling
2. Regions shift from rainforest → savannah