4-2-5-simpsons-index

Simpson’s Index of Diversity

• Once the abundance of different species in an area has been recorded the results can be used to calculate the species diversity or biodiversity for that area

• Species diversity looks at the number of different species in an area (species richness) but also the evenness of abundance across the different species in that area (species evenness)

• Simpson’s index of diversity (D) can be used to quantify the biodiversity of an area

Simpson’s index

• The formula is:

  

  •  Where:

    • n = total no. of organisms for a single species

    • N = total no. of organisms for all species

• To calculate Simpson’s Index:

  • Step 1: First calculate n / N for each species

  • Step 2: Square each of these values

  • Step 3: Add them together and subtract the total from 1

• To understand what the value of D means you need to know the following:

  • The value of D can fall between 0 and 1

    • Values near 1 indicate high levels of biodiversity

    • Values near 0 indicate low levels of biodiversity