Species Diversity Calculator Formula

Understand the math behind the species diversity calculator. Each variable explained with a worked example.

Use the Species Diversity Calculator

Formulas Used

Shannon Diversity Index

diversity_index = shannon_index

Maximum Possible H'

max_h = max_diversity

Evenness (J)

evenness_out = evenness

Average per Species

avg_per_species = total_individuals / num_species

Variables

VariableDescriptionDefault
num_speciesNumber of Species10
total_individualsTotal Individuals200
evennessDistribution Evenness(0-1)0.8
max_diversityDerived value= log(num_species)calculated
shannon_indexDerived value= log(num_species) * evennesscalculated

How It Works

How to Calculate Species Diversity

The Shannon Diversity Index (H') measures both species richness and evenness of distribution.

Formula

H' = -Sum(pi * ln(pi)) for each species

Simplified: H' = ln(S) * J

Where S = number of species, J = evenness (0-1)

Interpretation

  • H' < 1: Low diversity
  • H' = 1.5-3.5: Moderate diversity
  • H' > 3.5: High diversity

    • Worked Example

    A habitat with 10 species, 200 total individuals, and 0.8 evenness.

    num_species = 10total_individuals = 200evenness = 0.8
    1. 01Max diversity: ln(10) = 2.303
    2. 02Shannon index: 2.303 * 0.8 = 1.842
    3. 03Average per species: 200 / 10 = 20 individuals
    4. 04This indicates moderate diversity

    Frequently Asked Questions

    What is the Shannon Diversity Index?

    The Shannon Index (H') combines species richness (number of species) and evenness (how equally individuals are distributed). Higher values indicate more diverse communities.

    Why does evenness matter?

    A habitat with 10 species where 90% are one species is less functionally diverse than one where all 10 species are equally represented. Evenness captures this distinction.

    What is a healthy level of biodiversity?

    It depends on the ecosystem. Tropical forests may have H' > 4, while tundra naturally has H' < 1. The concern is when diversity decreases relative to historical levels.

    Ready to run the numbers?

    Open Species Diversity Calculator