Shannon Diversity Index Calculator
The Shannon Diversity Index H' = -Σ(pᵢ × ln(pᵢ)) measures biodiversity, where pᵢ is the proportion of species i. Typical range 1.5–3.5. Evenness E = H'/ln(S). Used for biodiversity assessment and conservation planning. Developed by Claude Shannon (1948).
🌍 Why This Matters for the Planet
Why It Matters
Biodiversity is essential for ecosystem function and resilience. The Shannon Index quantifies diversity by combining species richness and evenness. It helps ecologists compare sites, monitor restoration, and prioritize conservation.
How You Can Help
Enter counts for up to 6 species (use 0 for unused slots). The calculator computes H', evenness E, species richness S, effective species e^H', Simpson's D, H_max, total individuals, and dominant species %.
Key Insights
- ●H' > 3.0: high diversity (rainforest, coral reef)
- ●H' 2.0–3.0: good diversity (forest, grassland)
- ●H' < 1.0: low diversity (monoculture, disturbed)
- ●Evenness E=1 means perfectly even distribution
📋 Quick Examples — Click to Load
For educational and informational purposes only. Verify with a qualified professional.
🌎 Planet Impact Facts
Shannon Index H' typical range 1.5–3.5, rarely >4
— Ecology
Developed by Claude Shannon in 1948 from information theory
— History
Evenness E = H'/ln(S) ranges 0–1; E=1 means perfectly even
— Ecology
Used globally for biodiversity assessment and conservation
— Conservation
Effective species = e^H' answers species-equivalent diversity
— Ecology
Simpson's D = 1 - Σ(pᵢ²) is more sensitive to dominant species
— Ecology
The Shannon Diversity Index H' = -Σ(pᵢ × ln(pᵢ)) measures biodiversity, where pᵢ is the proportion of species i. Typical range 1.5–3.5, rarely >4. Higher = more diverse. Evenness E = H'/ln(S) where S = number of species; E ranges 0–1. Used for biodiversity assessment and conservation planning. Developed by Claude Shannon (1948) from information theory.
Key Takeaways
- • H' = -Σ(pᵢ × ln(pᵢ)); pᵢ = countᵢ / total for each species with count > 0
- • Evenness E = H'/ln(S); E=1 means perfectly even distribution
- • Effective species = e^H'; Simpson's D = 1 - Σ(pᵢ²)
- • Richness S = number of species with count > 0; H_max = ln(S)
Did You Know?
How the Formulas Work
Proportion pᵢ
pᵢ = countᵢ / total. Only species with count > 0 are included. Sum of pᵢ = 1.
Shannon H'
H' = -Σ(pᵢ × ln(pᵢ)). Natural log (ln) is used. Each species contributes -p×ln(p); maximum diversity when all p equal.
Evenness E
E = H'/ln(S). H_max = ln(S) is the maximum possible H' for S species. E normalizes H' to 0–1.
Simpson's D
D = 1 - Σ(pᵢ²). Probability that two random individuals are different species. Dominant species reduce D more.
Expert Tips
Compare to Reference Sites
Compare your H' to typical ecosystems: rainforest ~3.5, coral reef ~3.2, forest ~2.5, grassland ~2.0, farm ~0.8.
Sample Size Matters
Small samples underestimate richness. Use adequate quadrat size and replication for reliable H'.
Evenness vs Richness
Two sites can have same S but different H' if evenness differs. Check both richness and evenness.
Conservation Use
Shannon Index helps prioritize conservation areas and monitor restoration success over time.
Typical H' Ranges by Ecosystem
| Ecosystem | Typical H' | Context |
|---|---|---|
| Tropical Rainforest | 3.0–4.0 | Very high diversity |
| Coral Reef | 2.5–3.5 | High diversity |
| Temperate Forest | 2.0–2.8 | Moderate-high |
| Grassland | 1.5–2.5 | Moderate |
| Farm / Monoculture | 0.5–1.5 | Low diversity |
Frequently Asked Questions
What is the Shannon Diversity Index (H')?
The Shannon Diversity Index H' = -Σ(pᵢ × ln(pᵢ)) measures species diversity, where pᵢ is the proportion of species i. It combines richness (number of species) and evenness (how evenly distributed they are). Typical range 1.5–3.5, rarely >4. Higher H' = more diverse. Developed by Claude Shannon (1948) from information theory.
What is evenness E?
Evenness E = H'/ln(S) where S is species richness. E ranges 0–1. E=1 means perfectly even (all species equally abundant); E near 0 means one species dominates. Evenness tells you whether diversity comes from many species or from balanced abundances.
What is Simpson's D?
Simpson's D = 1 - Σ(pᵢ²) measures the probability that two randomly chosen individuals are different species. Higher D = more diverse. It is more sensitive to dominant species than Shannon; rare species contribute less to Simpson's D.
What is effective number of species?
Effective number of species = e^H'. It answers: 'How many equally abundant species would give the same H'?' For example, H'=2.0 → e²≈7.4 effective species. It makes H' interpretable in species-equivalent terms.
When is Shannon Index used?
Shannon Index is used for biodiversity assessment, conservation planning, ecological monitoring, and comparing sites. It is standard in ecology for quantifying community diversity. It works best with count data (individuals per species) from quadrats, transects, or surveys.
How do I interpret H' values?
H' < 1.0: low diversity (e.g., monoculture, disturbed site). H' 1.0–2.0: moderate. H' 2.0–3.0: good diversity (typical forest, grassland). H' > 3.0: high diversity (tropical rainforest, coral reef). Compare your site to reference ecosystems for context.
Key Statistics
Official Data Sources
⚠️ Disclaimer: The Shannon Diversity Index is a simplified measure of biodiversity. Real ecosystems have spatial heterogeneity, temporal variation, and sampling bias. Use for educational and exploratory purposes. For formal conservation or monitoring, consult ecological standards and professional ecologists.
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