Measure ecological diversity using Shannon-Wiener index, evenness, and Simpson's index.
Last updated: March 2026
Diversity score
ln(richness)
0 to 1
Dominance
Richness (number of species)
5
Total individuals
100
| Species | Count | % of Total |
|---|---|---|
| Species 1 | 45 | 45.0% |
| Species 2 | 30 | 30.0% |
| Species 3 | 15 | 15.0% |
| Species 4 | 8 | 8.0% |
| Species 5 | 2 | 2.0% |
Shannon diversity index (H') is a mathematical measure of species diversity in ecology. It accounts for both the number of species (richness) and how evenly distributed they are (evenness). A community with many equally abundant species has high diversity; a community dominated by one species has low diversity. Shannon index is widely used in ecology, conservation, and environmental monitoring.
The index is derived from information theory and ranges from 0 (only one species) to ln(S) where S is the number of species. Higher values indicate greater diversity. Evenness (J') normalizes Shannon index to a 0-1 scale: 0 means one species dominates completely, 1 means all species are equally abundant. Simpson's index (D) measures dominance as the inverse of concentration.
These metrics are critical for assessing ecosystem health, evaluating conservation efforts, and comparing biodiversity across different habitats or time periods. They help ecologists identify whether diversity is changing and why.
Bird Species in Two Habitats
It depends on context. Typical natural ecosystems range H' = 1.5 to 3.5. Very low values (<1) suggest dominance by few species (possible environmental stress). Very high values (>4) suggest rich, balanced communities with many species.
Richness is the count of species only (ignores abundance). Diversity accounts for both count AND evenness. Two habitats with same richness can differ greatly in diversity if abundance is unequal. Diversity is usually more informative.
Evenness (J', 0-1) indicates how balanced abundance is. J' ≈ 1 means all species equally common (high evenness). J' ≈ 0 means one species dominates (low evenness). Can have high richness but low evenness if one species dominates.
Both measure diversity, but emphasize different aspects. Shannon H' is intuitive and commonly used. Simpson's D emphasizes dominance (Σp²). For most ecological work, Shannon is standard. Simpson's is sometimes preferred when dominance matters more than rare species.
Yes, if methods are consistent. However, differences depend on sampling effort and methods. Use evenness (J') for normalized comparison. Be cautious comparing communities with very different richness levels—evenness may be more meaningful.
High diversity usually indicates a healthy, stable ecosystem with good ecological conditions. Low diversity can signal stress (pollution, habitat loss, invasive species). However, some ecosystems naturally have low diversity (deserts, tundra). Context matters!
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