1. Topic 2: The Ecosystem
2.3.5: Measuring Biodiversity
Simpson’s Index

2. Topic 2: The Ecosystem
2.3.5: Measuring Biodiversity
“Biodiversity or biological diversity is the variety of life in
all its forms, levels and combinations, including ecosystem
diversity, species diversity and genetic diversity” (IUCN,
UNEP and WWF, Rio Summit on Biodiversity, 1991).

3. Topic 2: The Ecosystem
2.3.5: Measuring Biodiversity
Simpson’s Diversity Index is a fairly simple way of
estimating species diversity in an ecosystem.
The formula is:
Simpson’s D.I
= N (N – 1)
where: N = total number of individuals
Σ n (n – 1)
and n = total numbers of individuals of each species

4. Topic 2: The Ecosystem
2.3.5: Measuring Biodiversity
An example
Species Number of individuals Number of individuals
in Ecosystem 1 in Ecosystem 2
A 23 2
B 28 2
C 22 1
D 27 93
Total individuals in 100 98
ecosystem

5. Topic 2: The Ecosystem
2.3.5: Measuring Biodiversity
Species Number of Number of
individuals in individuals in
Ecosystem 1 Ecosystem 2
A 23 2
B 28 2
For Ecosystem 1: C 22 1
D 27 93
Total individuals in 100 98
Simpson’s D.I. = ecosystem
100 x (100 – 1) = 4.08
[23x(23-1)] + [28x(28-1)] + [22x(22-1)] + [27x(27-1)]
= N (N – 1)
where: N = total number of individuals
Σ n (n – 1)
and n = total numbers of individuals of each species

6. Topic 2: The Ecosystem
2.3.5: Measuring Biodiversity
The larger the number
the greater the diversity

7. Topic 2: The Ecosystem
2.3.5: Measuring Biodiversity
So what about ecosystem 2?
Species Number of individuals Number of individuals
in Ecosystem 1 in Ecosystem 2
A 23 2
B 28 2
C 22 1
D 27 93
Total individuals in 100 98
ecosystem