7.1: Introduction to What is Biodiversity?

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Fig_3.0_NinaR-2.jpg — A “silverback” mountain gorilla (*Gorilla beringei beringei*, EN) in Mgahinga Gorilla National Park, Uganda. Once thought to be one species, genetic analyses have shown that there are two gorilla species, each with two subspecies. Thanks to the efforts of dedicated conservationists and local communities in the Albertine Rift, the IUCN downlisted the mountain gorilla from Critically Endangered to Endangered in 2018. The three other subspecies are still considered Critically Endangered. Photograph by Nina R, https://www.flickr.com/photos/150102727@N06/31467129021, CC BY 2.0.

Conservation biology aims to improve the protection of biodiversity—that is, all the species, genetic diversity, and ecosystems on Earth. By this definition, the process of documenting life on Earth requires us to consider biodiversity on three different levels (Figure 7.1.1):

Species diversity: The full variety of species, from single-celled organisms like bacteria to larger multicellular organisms like animals and everything in between.
Genetic diversity: The full range of variability in genetic material within a species. This variation can occur spatially as differences between populations or as differences between individuals of the same population.
Ecosystem diversity: The full variety of ecosystems—i.e., assemblages of species and the physical environments in which they live.

Figure 7.1.1 A region’s biodiversity includes the full complement of that area’s species diversity (all the area’s species), genetic diversity (the full range of genetic variation found within each of those species), and ecosystem diversity (the variety of ecosystems and ecological processes). CC BY 4.0.

The relationship between species, genetic, and ecosystem diversities is complex and interdependent. That is, a species cannot exist without genetic diversity or ecosystem diversity, and vice versa. For that reason, it is virtually impossible to affect one aspect of diversity without affecting the other. We can therefore think of species, genetic, and ecosystem diversities simply as different ways to measure the variety of life.