Biodiversity & Ecosystem Stability
Biodiversity describes the variety of life, while ecosystem stability describes how ecological systems respond to disturbance and change. These ideas are closely connected but are not identical.
Biodiversity & Ecosystem Stability
What Is Biodiversity?
Biodiversity is the variety of life in a particular area or on Earth as a whole. It can be considered at several levels, including genetic diversity within species, species diversity within communities, and ecosystem diversity across landscapes.
In ecology, biodiversity is not simply a count of how many organisms are present. Scientists may ask which species are present, how abundant those species are, how genetically different populations are, and how many different ecosystems occur across a region.
Biodiversity describes variety. Species richness tells you how many species are present, while species evenness describes how evenly individuals are distributed among those species.
Levels of Biodiversity
Genetic Diversity
Variation in genes among individuals or populations of the same species. Genetic variation can provide the raw material for natural selection.
Species Diversity
The variety of species in a community, including both the number of species and their relative abundances.
Ecosystem Diversity
The variety of ecosystems and habitats across a region, such as forests, wetlands, grasslands, rivers, and coastal systems.
Species Richness and Evenness
Species richness is the number of different species in a community. A community with 12 species has greater richness than a community with 5 species, assuming the comparison is made over equivalent sampling areas.
Species evenness describes how evenly individuals are distributed among the species present. Two communities can have the same richness but very different evenness.
How Does Biodiversity Relate to Ecosystem Stability?
Ecosystem stability describes how an ecosystem responds to disturbance and changes over time. Two useful ideas are resistance and resilience. Resistance is the ability to remain relatively unchanged when disturbed. Resilience is the ability to recover after a disturbance.
Higher biodiversity can sometimes increase stability because different species may perform overlapping ecological roles. If one species declines, another species may continue performing a similar function. This is sometimes described as functional redundancy.
Stay stable
The ecosystem changes relatively little when a disturbance occurs.
Recover
The ecosystem returns toward its previous structure or function after a disturbance.
However, biodiversity does not guarantee stability under every condition. The relationship depends on the ecosystem, the disturbance, and which species or functions are affected. A strong answer should explain the ecological mechanism rather than simply state that “more biodiversity equals more stability.”
Mechanisms That Can Increase Stability
Species differ in how they respond to environmental conditions. A drought may strongly affect one plant species but have a smaller effect on another. If several species contribute to the same ecosystem function, differences in their responses can reduce the impact of a disturbance on the overall function.
Biodiversity can also increase the number of interactions within a food web. These interactions can create multiple pathways for energy and matter to move through an ecosystem. Again, the exact outcome depends on the organisms and conditions involved.
On a test, connect biodiversity to stability by explaining what happens to ecosystem functions when one species is reduced or removed.
What Happens When Biodiversity Is Lost?
Loss of biodiversity can reduce the number of ecological roles represented in a community. It may also reduce genetic variation, simplify food webs, and make some ecosystem functions more dependent on a smaller number of species.
Major drivers of biodiversity loss include habitat loss and fragmentation, invasive species, pollution, overexploitation, and climate change. These pressures can interact rather than operating independently.
Common Misconceptions
If You See This on a Test, Think This
Quick Practice
1. What is biodiversity?
2. Two communities each contain five species. Community A has nearly equal numbers of individuals in all five species, while Community B is dominated by one species. Which has greater evenness?
3. What is the difference between resistance and resilience?
4. Why might biodiversity help an ecosystem maintain function after a species declines?
5. Does high biodiversity guarantee that an ecosystem will never change?
Key Takeaways
- Biodiversity is the variety of life at genetic, species, and ecosystem levels.
- Species richness is the number of species present.
- Species evenness describes how evenly individuals are distributed among species.
- Ecosystem stability can involve resistance and resilience.
- Different species can respond differently to the same disturbance.
- Functional redundancy can help maintain ecosystem functions when one species declines.
- Biodiversity can contribute to stability, but it does not guarantee a particular outcome.
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