Species refers to the number of species within the vision extent. We estimate the number of species for each taxon separately, including plants, freshwater fish, marine fish, amphibians, reptiles, birds, and mammals. To determine the number of species (aka species richness), we use species-area relationships that are specific to each taxa. The species-area relationship is one of the best documented relationships of community ecology. Across many taxa and in many different locations, scientists have demonstrated that the number of species increases as the area sampled increases. Similarly, scientists have shown that the number of species in an area increases the closer the area is to the equator. Both of these principles have been incorporated into the species-area relationships used in our model.
The general form of the species area curve is:
Potential species richness = c * Az
Where:
c = coefficient of the species-area curve
z = exponent of the species-area curve
A = area of interest
Both c and z vary by taxon.
In our model:
Potential species richness = (ca * Az) * (cm * (1 / L))
Where:
ca = coefficient for area
z = exponent for area
cm = coefficient for latitude
A = area of interest in square kilometers, weighted by taxon
L = latitude in degrees
Both c and z vary by taxon.
Depends upon:
—Parameters: equivalent latitude, minimum habitat area, probability of species in habitat, species-area coefficient a, species-area coefficient b and species-area coefficient m