What is biological diversity?


Biological diversity (or biodiversity) refers to the variety of life forms in a given area or within a taxonomic group of organisms. Biological diversity can be considered at any of a wide assortment of different scales. For instance, it can refer to:

  • genetic diversity within populations, subspecies or species
  • species diversity* within habitat patches, communities, regions or taxonomic groups
  • diversity of habitat structure within patches, communities or landscapes
  • patch diversity in a mosaic of different patch types within communities or landscapes
  • diversity of communities within landscapes or regions
  • diversity of ecoregions within a continent or biome


Living wild species are like a library of books still unread. Our heedless destruction of them is akin to burning the library without ever having read its books.” —Congressman John Dingell, 1990 (essay in Balancing on the Brink of Extinction: the Endangered Species Act and Lessons for the Future)


The one process now going on that will take millions of years to correct is the loss of genetic and species diversity by the destruction of natural habitats. This is the folly our descendants are least likely to forgive us.” —E. O. Wilson, 1984 (Biophilia)


The outstanding scientific discovery of the twentieth century is not television, or radio, but rather the complexity of the land organism. Only those who know the most about it can appreciate how little we know about it. The last word in ignorance is the man who says of an animal or plant: ‘What good is it?’ If the land mechanism as a whole is good, then every part is good, whether we understand it or not. If the biota, in the course of aeons, has built something we like but do not understand, then who but a fool would discard seemingly useless parts? To keep every cog and wheel is the first precaution of intelligent tinkering.” —Aldo Leopold, 1953 (Round River: From the Journals of Aldo Leopold)


*PABS maintains a running tally of Pennsylvania’s wild species called the Box Score.

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