2.1K Planetary boundaries model and biosphere integrity Notes

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 represents a safe operating limit within which humanity can continue to thrive without causing irreversible environmental change.
3. Crossing these boundaries increases the risk of tipping points that can destabilize global systems.
4. One of these nine boundaries is biosphere integrity, which focuses on the health, diversity, and functioning of ecosystems and species that sustain life on Earth.

Understanding Biosphere Integrity

1. Biosphere integrity reflects how intact and functional Earth’s biological systems are.
2. It encompasses both:
   1. Genetic diversity: variation within and between species that enables adaptation.
   2. Functional diversity: the roles species play (e.g., pollination, decomposition, nutrient cycling).

Interrelationship Between Ecosystems and Species Diversity

1. Ecosystem health and species diversity are mutually dependent:
   1. Diverse species ensure resilience, enabling ecosystems to recover from disturbances.
   2. Stable ecosystems provide habitats and resources that sustain species populations.
2. When biodiversity declines, ecosystems lose resilience, leading to ecosystem collapse and further biodiversity loss in a positive feedback loop.

Human Activities and Loss of Biosphere Integrity

1. Habitat destruction and fragmentation (deforestation, urbanization).
2. Pollution (air, water, and soil contamination).
3. Climate change altering temperature, rainfall, and habitats.
4. Invasive species displacing native biodiversity.
5. Overexploitation of resources (overfishing, hunting, mining).

Evidence for Crossing the Biosphere Integrity Boundary

Extinction Rates

1. The background extinction rate (natural rate) is 0.1–1 E/MSY (extinction per million species-years).
2. The current human-induced rate is estimated at 100–1000 E/MSY, meaning extinctions are occurring 100 to 1000 times faster than natural rates.
3. This level indicates the biosphere integrity boundary has been transgressed.

Biodiversity Intactness Index (BII)

1. BII measures the average abundance of native species compared to an undisturbed ecosystem.
2. A BII ≥ 90% = within safe boundary (ecosystem resilient).
3. A BII between 30–90% = reduced resilience and ecosystem degradation.
4. A BII ≤ 30% = ecosystem collapse risk.

Why Reversal is Urgent

1. The biosphere supports all life and underpins every other planetary boundary (e.g., climate regulation, nutrient cycling, freshwater stability).
2. Without biosphere integrity, Earth’s resilience declines, making other boundaries harder to maintain.
3. Reversing biodiversity loss is essential to avoid irreversible tipping points where ecosystems collapse and new, less habitable equilibria emerge.

Strategies to Reverse Loss of Biosphere Integrity

1. Habitat Protection and Restoration

1. Preserve existing ecosystems such as forests, wetlands, coral reefs, and grasslands.
2. Restore degraded ecosystems through reforestation, wetland rehabilitation, and soil recovery.
3. Create ecological corridors to connect fragmented habitats and allow species migration.

2. Species Conservation

1. Protect endangered species through captive breeding, reintroduction, and anti-poaching measures.
2. Maintain genetic diversity to enhance species’ adaptability to environmental change.

Example

Conservation of the black rhinoceros in Kenya through anti-poaching patrols and community partnerships has stabilized its population.

3. Sustainable Resource Management

1. Adopt sustainable agriculture and forestry (e.g., agroforestry, selective logging).
2. Limit overfishing and hunting to prevent species decline.
3. Manage water use to maintain wetland and freshwater ecosystems.

4. Legislation and Protected Areas

1. Expand protected areas and enforce biodiversity laws
   1. Convention on Biological Diversity (CBD)
   2. CITES (Convention on International Trade in Endangered Species)
   3. UN Sustainable Development Goals (SDG 14 & 15)
2. Implement international agreements that prioritize ecosystem-based management.

5. Reducing Pollution and Climate Change

1. Transition to renewable energy and low-impact technologies.
2. Reduce pesticide and plastic use that harm ecosystems.
3. Curb greenhouse gas emissions to prevent temperature and ocean chemistry shifts.

6. Community Involvement and Education

1. Engage local communities in conservation and sustainable livelihoods.
2. Promote education about biodiversity’s importance to climate, economy, and well-being.

Protecting Niche Requirements

1. Each species occupies a unique ecological niche, its role and habitat requirements in an ecosystem.
2. By protecting ecosystem integrity, we preserve the niches necessary for species survival.
3. When ecosystems are restored (e.g., replanting trees, reintroducing apex predators), species interactions recover, strengthening biosphere integrity.