Is biodiversity increased by adding exotic species to the landscape?
This question presents one of the most common misconceptions about biodiversity. It is fairly common for people to think that biodiversity simply means the number of species present in a particular place. If this were true, and if alien species were not capable of displacing natives or affecting ecological functions, then the addition of exotics to the local plant community would indeed increase biodiversity. But biodiversity is more than the sum total of species, and is often discussed in terms of: 1) species diversity, 2) genetic diversity, and 3) ecological diversity. Species diversity can be further explained as species richness and evenness. Richness is simply the total number of species in a given area. Evenness is a measure of how well represented each species is. As an example, suppose that two similar areas contain 1,000 individuals of trees from the same 10 species. If in area one each species had 100 individuals, then evenness would be high. If in area two, nine of the speci
