Skip to main content
Calcimator

Island Biogeography Calculator

Predict species richness from island area and distance using the species-area relationship (S = cA^z) from MacArthur & Wilson's theory.

Inputs

km²
mi

Results

Predicted Species Richness

26.6

Species at Half Area22.4
Species at Double Area31.6
% Lost if Area Halved15.9%
Immigration Rate3.68 spp/time
Extinction Rate4.73 spp/time
Isolation LevelModerate
Species Gained Double5.03
Equilibrium Species15.12
How to Use This Calculator
  1. Enter Island Area (km2) and Distance from Mainland (km).
  2. Set the z Exponent (typically 0.20-0.35) and c Constant from the species-area relationship.
  3. Review Predicted Species Richness, and the species count at half and double the current area.
  4. Check % Lost if Area Halved to evaluate the conservation impact of habitat fragmentation.
  5. Use Immigration and Extinction Rates to understand equilibrium dynamics on the island.

How the result changes with c Constant

c ConstantPredicted Species Richness
100265.9
350930.7
6501,728.4
9002,393.2

What each input means

Island Area
Total area of the island or habitat fragment in square kilometers.
Distance from Mainland
Distance from the nearest mainland or large source habitat in km. Affects immigration rate.
z Exponent
Species-area exponent. Typical values: 0.20-0.35 for oceanic islands, 0.12-0.17 for mainland habitats.
c Constant
Taxon- and region-specific constant. Depends on the taxonomic group and biogeographic region.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Island Area = 50, Distance from Mainland = 100, z Exponent = 0.25, c Constant = 10 = 4 input(s) provided
  2. Calculate Predicted Species Richness
    Predicted Species Richness
    26.6 = 26.6
  3. Calculate Species at Half Area
    22.4 = 22.4
  4. Calculate Species at Double Area
    31.6 = 31.6

Related Calculators

The questions that sit next to this one — chosen by subject, including calculators filed under a different category.

Ecology

Species Diversity Index Calculator

Calculate Shannon-Wiener (H'), Simpson's Diversity Index, and evenness from species abundance data for up to 10 species.

Ecology

Population Growth Calculator

Model logistic and exponential population growth over time using initial population, growth rate, and carrying capacity.

Ecology

Habitat Suitability Score Calculator

Calculate a Habitat Suitability Index (HSI) from food, water, cover, and disturbance scores using the geometric mean method.

Marine Biology

Marine Protected Area Size Calculator

Estimate minimum MPA size from species home range, viable population targets, species-area relationships, and protection level requirements.

Conservation

Biodiversity Index Calculator

Calculate Shannon-Wiener, Simpson's, and Margalef biodiversity indices from species count data for conservation assessment.

More in Environment, Weather & Climate.