2.5C Ecosystem resilience Notes

1. The ability of an ecosystem to tolerate disturbances and maintain equilibrium depends on its diversity and resilience.
2. Ecosystems naturally experience disturbances, such as fires, floods, storms, volcanic eruptions, or human activities, but their response determines their long-term stability and sustainability.
3. Some systems can absorb shocks and return to their original state, while others shift into alternative stable states with new sets of species and ecological conditions.

Key Components Influencing Ecosystem Resilience

1. Biodiversity (Species and Genetic Diversity)

1. High biodiversity means more species are available to perform similar ecological functions (known as functional redundancy).
2. If one species declines or goes extinct, others can fill its role, maintaining stability in energy flow and nutrient cycling.
3. Genetic diversity within species enhances adaptability to changing conditions, improving survival under stress such as drought, disease, or temperature shifts.

2. Habitat Diversity

1. Ecosystems with diverse habitats (e.g., wetlands, forests, rivers) offer multiple niches, supporting a wide range of organisms.
2. This diversity cushions the ecosystem from large-scale collapse, as different habitats recover at different rates.

3. Trophic Complexity

1. Complex food webs (many interlinked feeding relationships) distribute energy more efficiently and prevent chain reactions of species loss.
2. Simple systems (e.g., monocultures) collapse more easily when a single species fails.

4. Functional Diversity

1. Refers to the variety of ecological roles or “functions” organisms perform, such as nitrogen fixation, decomposition, and pollination.
2. Greater functional diversity ensures the ecosystem continues functioning even when individual species are affected.

Human Impacts on Ecosystem Resilience and Succession

1. Deforestation

1. Removes canopy cover, alters the microclimate, and exposes soil to erosion.
2. Loss of biodiversity reduces redundancy and resilience.

2. Agriculture and Grazing

1. Overgrazing reduces vegetation cover → increases erosion and nutrient loss.
2. Intensive agriculture simplifies ecosystems (monocultures), reducing species and genetic diversity.
3. Soil compaction and fertilizer use alter nutrient cycling and water infiltration.

3. Mining and Urbanization

1. Removal of vegetation and topsoil destroys soil structure and microbial communities.
2. Pollution from chemicals disrupts aquatic and terrestrial food webs.
3. Recovery often slow due to severe alteration of abiotic factors.

4. Burning and Fire Management

1. Controlled fires can support natural succession (e.g., savanna ecosystems).
2. Uncontrolled fires destroy seed banks, alter nutrient cycles, and push ecosystems toward degraded states.
3. Frequent burning may prevent recovery of forests and lead to grassland replacement.

Alternative Stable States

1. An alternative stable state occurs when an ecosystem crosses a threshold and reorganizes into a new structure with different dominant species and functions.
2. These new states often have lower biodiversity and reduced productivity.
3. Recovery to the original state may be impossible without human intervention (e.g., restoration programs).