IB Environmental systems and societies 2.1K Planetary Boundaries Model and Biosphere Integrity Notes

Planetary Boundaries: Nine Limits That Keep Earth Safe for Humanity

The Planetary Boundaries Model

1. The planetary boundaries model, developed by Johan Rockström and colleagues, defines nine critical Earth system processes that regulate the planet's stability.
2. Each boundary marks a safe operating space within which humanity can keep thriving without triggering large, hard-to-reverse environmental change.
3. Crossing a boundary raises the risk of tipping points that can push global systems into a new, less stable state.
4. One of these nine boundaries is biosphere integrity, the health, diversity, and functioning of the living systems that sustain life on Earth.

Biosphere Integrity: Genetic and Functional Diversity Underpin Every Other Boundary

1. Biosphere integrity measures how intact and functional Earth's biological systems are.
2. Genetic diversity is the variation within and between species that lets populations adapt to change.
3. Functional diversity is the range of roles species perform, such as pollination, decomposition, and nutrient cycling.

How Ecosystem Health and Species Diversity Depend on Each Other

1. Diverse communities give ecosystems resilience, the capacity to recover after a disturbance.
2. Stable ecosystems in turn supply the habitats and resources that keep species populations going.
3. When biodiversity falls, ecosystems lose resilience, driving further loss in a positive feedback loop toward collapse.

Human Pressures That Erode Biosphere Integrity

1. Habitat destruction and fragmentation from deforestation and urbanization.
2. Pollution of air, water, and soil.
3. Climate change shifting temperature, rainfall, and habitat ranges.
4. Invasive species displacing native biodiversity.
5. Overexploitation through overfishing, hunting, and mining.