objects/species-area-curve.html

Species Area Curve

Observations of number species vs. the size of their habitat

area km^2	number of species
2000	120
1000	61
500	30
250	15
4000	202
10000	299

lead to relationships that look like this

equation is:
S = C*A^z

S is number of species
C is a fit constant
A is the area
z is another fit constant

Plotting data looks like a log curve

because of the curve, decreasing the number of species has little effect at the far top right

but as you loose more and more species the relative loss from the same change in area

in the figure below, decreasing the area by about 4 times only decreases the species by 2 times

some species area curve are even "shallower"

decreasing the area by 10 times only results in a 2 fold decrease in species

(but remember by "only" we are talking about extinction, potentially irreversibly)

some species area curve are even "shallower"

decreasing the area by 10 times only results in a 2 fold decrease in species

(but remember by "only" we are talking about extinction, potentially irreversibly)

 

Log-log transform of this gives a straight line

log(S) = log(C*A^z)

log(S) = z*log(A) + log(C) (which is just like y = mx+b except with the axes being log of y and log of x.