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Defining Biodiversity

Defining Biodiversity

There are many ways to phrase the definition of biological diversity, or biodiversity. They all mean the same thing but say it in different ways.

  • "The variety of living organisms, from genetic diversity through species, to higher taxonomic levels...and includes the variety of habitats, ecosystems, and landscapes in which the species are found." From the King County Comprehensive Plan and the King County Biodiversity Report
  • “The full range of life in all its forms.” From the Washington Biodiversity Council in their Biodiversity Conservation Strategy. Their definition also includes "the interactions that sustain each species, such as predator-prey relationships, and the physical processes on which life depends, including chemical and nutrient cycling, water filtration, and climate regulation.”
  • "Species, the genes they contain, the communities and ecosystems they form, and the processes that connect them." From the book entitled Precious Heritage; the Status of Biodiversity in the United States.

 Genes, species, ecosystems, and processes... We can briefly explore each of these topics.

Genes, or Genetic Diversity

Genetic diversity might be the most important level of biodiversity to conserve because it is the most fundamental. When adequate amounts of habitat are available and populations are large enough, resilient enough, and are able to move around in time and space naturally, plants and animals can remain genetically diverse. When they are genetically diverse, they can respond to changing environments, competition, predation, and major disturbances. When these responses become permanent changes, evolution and adaptation are taking place.


When most people think of biodiversity, they think of plant and animal species. Our Species of Interest page has information about species in King County. Here are a few snapshots:
  • Approximately 220 species of breeding and non-breeding birds are usually seen on an annual basis in King County.
  • At least 13 species of amphibians and 8 species of reptile are thought to breed in the county.
  • There are between 70 and 80 mammal species that inhabit or visit King County -- the visitors are some of the whales that traverse Puget Sound.
  • About 50 species of native fish (and 20 species of introduced fish) are found in the freshwater streams, rivers, ponds, and lakes of King County.
  • In the County’s marine environment, over 200 species of fish, some 500 species of invertebrate animals, and 8 species of marine mammals can be found.
  • An astounding 1,249 (383 introduced) species of vascular plants have been identified in the county.
  • And there are thousands of terrestrial invertebrate species

Habitats and Ecosystems

Because of its size, topography, and geology, the diversity of landscapes and habitats in King County is dramatic. From the imposing presence of the Cascade Mountains to rare and sensitive lowland bogs, King County possesses an astonishing array of landforms and habitats. The aquatic habitats of King County include a variety of wetland types, large and small lakes, rivers and streams together with their riparian areas, and habitats of the marine waters of the County. The terrestrial habitats of King County include distinctive land-based vegetation communities found in the lowlands, highlands, and sub-alpine and alpine areas of the County. Although some of these habitat types are relatively undisturbed (especially in subalpine and alpine areas), many have been dramatically altered as the result of human-induced changes over the last century and a half.


Ecoregions are the largest unit of biodiversity. A system of mapped ecological regions, or ecoregions, is very helpful for using what is known about soils, elevation, hydrology, geology, and climate to better understand the species present in an ecosystem and how they interact with one another and the landscape. Ecoregions provide an ecological perspective for planning and management of natural resources and a useful framework for the discussion of marine, freshwater, and terrestrial environs of the county. The King County Ecoregion page includes information on what ecoregions are found in the county, and what those ecoregions are composed of. 

Natural processes

In order for genes, species and populations, and habitats and ecosystems to thrive, natural processes must occur. Ecosystems and habitats suitable for particular species communities are the result of various geologic, hydrologic, and biologic processes.