Produced by the Native Plant Society of Oregon, this article argues that, while the use of native species is an accepted tenet of conservation, the term “native” is not necessarily well understood; they attempt to clarify the term.
“Any definition of a native species, native ecosystem, or native landscape requires an historical benchmark” [Wilson 1991: 16]. Over the past 20,000 years, “vegetation in the Willamette Valley has changed dramatically with changing climate. Vegetation in a single place has probably varied from boreal parkland, to conifer forest, to oak savanna, to prairie. Each climatic phase supported a different flora” [Wilson 1991: 16]. Each of these vegetation types was native to a particular place, according to particular climatic conditions that changed overtime. The vegetation that developed in the past 10,000 years – the current Holocene period of climate stability – is thus the relevant reference.
“For the Pacific Northwest, the period that ended with Euro-American settlement is a natural historical benchmark. This period lasted long enough to have a significant impact on the vegetation of the region. The climates of much earlier times were different enough to limit their usefulness in defining today’s ecosystems” [Wilson 1991: 16]. Thus, “any species that had occurred in a particular ecological habitat [of the Pacific Northwest] before Euro-American settlement is a species native to that habitat” [Wilson 1991: 17].
A native ecosystem, then, is one dominated by native plants, animals and microorganisms that occurred together before the time of Euro-American settlement. Key species – for example, the dominant photosynthesizing plants, the top carnivores, the important decomposers, the nitrogen-fixers – must be present for a native ecosystem to persist and function on its own. To artificially maintain a conserved or restored ecosystem without all of its crucial components is both difficult and expensive. The species of native ecosystem must also occur together in nature. For example, landscaping with an artificial mixture of native species like vine maple, blue bunch wheatgrass, and Jeffrey pine does not produce a native ecosystem. These species are native to different areas within Oregon, but they would not naturally grow together in the same ecosystem. Restoration of native ecosystems must also account for proper structure and appearance. For example, a red fescue lawn does not have the structural complexity and species diversity exhibited by native bunchgrass prairies [Wilson 1991: 17].
Key species – for example, the dominant photosynthesizing plants, the top carnivores, the important decomposers, the nitrogen-fixers – must be present for a native ecosystem to persist and function on its own. To artificially maintain a conserved or restored ecosystem without all of its crucial components is both difficult and expensive [Wilson 1991: 17].
Wilson, Mark V., David E. Hibbs & Edward R. Alverson, 1991, Native plants, native ecosystems and native landscapes: an ecological definition of "native" will promote effective conservation and restoration, Kalmiopsis: Journal of the Native Plant Society of Oregon, https://www.npsoregon.org/kalmiopsis/kalmiopsis_v01x.pdf