31.6
species
1.5
2
31.6
species
1.5
2
The Species-Area Relationship Calculator predicts the number of species expected in a given area using the classic power-law relationship from island biogeography. The species-area relationship (SAR) is one of the oldest and most well-established patterns in ecology, describing how species richness increases with habitat area.
This relationship is fundamental to conservation biology for predicting species loss from habitat destruction, designing nature reserves, and understanding biodiversity patterns on islands and habitat fragments.
The species-area relationship follows the power function:
S = c × Az
Where:
On a log-log scale, this becomes a linear relationship: log(S) = log(c) + z × log(A).
Inputs
Results
S = 10 x 100^0.25 = 10 x 3.16 = 31.6 species predicted for a 100 km² island with these parameters.
Inputs
Results
A 100-fold increase in area from 100 to 10,000 km² roughly triples species richness from 31.6 to 100.
For oceanic islands, z typically ranges from 0.20 to 0.35, with 0.25 being a commonly cited average. For habitat fragments on continents, z tends to be lower (0.12-0.18) because of rescue effects from surrounding habitat. Very isolated archipelagos may have z values approaching 0.35.
The constant c represents the number of species expected in one unit of area. It varies by taxonomic group, geographic region, and productivity. Tropical regions typically have higher c values than temperate regions for the same taxonomic group, reflecting higher baseline biodiversity.
The species-area relationship predicts that reducing habitat area will cause species extinctions. A common rule of thumb is that a 90% reduction in area leads to approximately 50% species loss (when z = 0.25). This helps conservation biologists estimate extinction risk from deforestation and habitat fragmentation.
Roboculator Team
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