There are many ways to phrase the definition of biodiversity. They all mean the same thing but say it in different ways.
The King County Comprehensive Plan and the King County Biodiversity Report both use this definition: "Biological diversity, or biodiversity, is the variety of living organisms, from genetic diversity through species, to higher taxonomic levels, which is the classification of plants and animals according to their presumed natural relationships, and includes the variety of habitats, ecosystems, and landscapes in which the species are found."
A simpler definition of biodiversity is provided by the Washington Biodiversity Council in their Biodiversity Conservation Strategy (2007): “The full range of life in all its forms.” Their definition continues and “includes the habitats in which life occurs, the ways that species and habitats interact with each other, and the physical environment and the processes necessary for those interactions….This definition includes all species found within the state, from tiny soil microbes to towering Douglas-firs. The 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.”
A definition found in the book entitled Precious Heritage; the Status of Biodiversity in the United States, very eloquently states, "Biodiversity is composed of species, the genes they contain, the communities and ecosystems they form, and the processes that connect them."
Let's break that down. Species, their genes, communities and ecosystems, and processes... We can explore each of these topics.
Genes, or Genetic DiversityGenetic diversity is arguably the most important level of biodiversity to conserve, because it is the most fundamental. How is this accomplished? By conserving all the other levels of biodiversity. 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 enough to respond to changing environments, competition, predation, and major disturbances. When these responses become permanent changes, evolution and adaptation are taking place.
SpeciesWhen most people think of biodiversity, they think of species. This is understandable, because plants and animals can be seen with the naked eye (as opposed to genes), and because it is often easier to think of conservation in terms of an individual species and its needs versus that of an entire ecosystem.
Approximately 220 species of breeding and non-breeding birds are usually seen on an annual basis in King County. Based on an analysis by the State of Washington, 12 species of amphibians and 8 species of reptile are thought to breed in the county. There are somewhere between 70 and 80 mammal species that inhabit or at least 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.
Our Species of Interest page has lots more information about species in King County.
Habitats and EcosystemsBecause 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 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 are the result of human-induced changes in the landscape over the last century and a half. 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.
EcoregionsA system of mapped ecological regions, or ecoregions, is very helpful for using what is known about soils, slope, location, and climate to ascertain ecosystem information. Ecoregions provide an ecological perspective for planning and management of natural resources. U.S. Environmental Protection Agency (EPA) ecoregions are a nested biogeographical classification system, which result in units that denote areas of general similarity in ecosystems. Ecoregions provide a useful framework and background 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 the ecoregions are composed of. The page also includes links to how other agencies use ecoregions as a natural resource planning tool.