Biodiversity Index Calculator
Simpson's Index of Diversity.
Formula first
Overview
Simpson's Index of Diversity (D) measures the probability that two individuals randomly selected from a sample will belong to different species. It integrates species richness and evenness into a single value, where a result closer to 1 indicates high diversity and a value closer to 0 indicates a monoculture.
Symbols
Variables
D = Diversity Index, (n/N)^2 = Sum of (n/N)^2
Apply it well
When To Use
When to use: Use this formula when evaluating the ecological health of a habitat or comparing different biological communities. It is best suited for scenarios where you have a sample representing the total population and want to account for the dominance of specific species rather than just the total number of species.
Why it matters: This index is a standard metric in conservation biology for identifying resilient ecosystems that can better withstand environmental changes. High biodiversity indices often correlate with complex food webs and greater ecosystem stability, helping scientists prioritize areas for environmental protection.
Avoid these traps
Common Mistakes
- Confusing D with the sum term.
- Using percentages instead of proportions.
One free problem
Practice Problem
A biologist surveying a coastal tide pool finds 2 species: 15 sea anemones and 35 hermit crabs. Calculate the Biodiversity Index (D) for this community.
Solve for:
Hint: First find the total population N, then calculate the sum of (n/N)² for both species before subtracting from 1.
The full worked solution stays in the interactive walkthrough.
References
Sources
- Wikipedia: Simpson index
- Britannica: Simpson's diversity index
- Ecology: From Individuals to Ecosystems (Begon, Townsend, Harper)
- Magurran, Anne E. Ecological Diversity and Its Measurement. Princeton University Press, 2004.
- Begon, Michael, Colin R. Townsend, and John L. Harper. Ecology: From Individuals to Ecosystems. Wiley-Blackwell, 2006.
- AQA A-Level Biology — Biodiversity