Equality (biodiversity)
The equality ( English "species evenness" or "species equitability", also the balance of species or species equality ) is a measure that can be used to characterize biodiversity . As a measure of uneven distribution , the equality expresses how often or rarely individuals of a species occur in a certain biotope , based on the number of individuals of the other species occurring in this biotope. The higher the equality, the more evenly the numbers of individuals are distributed between the species.
In addition to species diversity, the balance of species is an important criterion for assessing the threat to species in a habitat. Often the equality sinks, since heavy pollution of the habitat ( environmental pollution , habitat fragmentation ) leads to the fact that the species spectrum is increasingly dominated by a few resistant (or Eurocean ) species.
example
If there are only two species in a biotope, namely foxes and dogs , then with 40 foxes and 1,000 dogs there would be little equality. But if there are 40 dogs and 42 foxes, the equality would be very high. If ten species occur in a biotope and a total of 100 individuals are counted, the maximum equality would be achieved with ten individuals of each species. On the other hand, the minimum equality would be given for 91 individuals of one species and one individual for each of the remaining nine species.
The most complete representation of equality provides a logarithmic representation of the number of individuals versus the rank of their frequency. In addition, there are several approaches that express equality as a single, normalized number. In this form, the evenness flows into the Shannon index .
Individual evidence
- ^ A b Peter A. Henderson: Practical methods in ecology . Wiley & Sons, Malden 2003, ISBN 1-405-10244-6 , pp. 121-122. .
- ↑ Gudrun Back, Michael Türkay : A measure for the balance of species (equality) . In: Janich, Gutmann, Prieß: Biodiversity . Springer, Berlin 2001, ISBN 3-540-42658-2 , pp. 246-251. .