Biologists have always been intrigued by questions of origin and dispersal. How and why do species arise? How do they spread from their points of origin? Are there hotspots or centers of evolution and dispersal? Thus, through the years biogeography has been a fertile field of scientific research and discourse, and the question of means of dispersal has long fueled vigorous debate and disagreement. Given present-day understanding of plate tectonics, consideration of plate movements over geologic time must now be added to the traditional arguments about long-distance dispersal versus incremental migration.
In recent geologic time, of course, human intervention has been a factor as well, and increasingly in our day we must reckon with humans as agents of dispersal in all of our speculations about the spread of species. Increasingly, too, biologists are finding that, in the name of conservation, some of their most natural, vital allies are confounding the questions of origin and dispersal with well-meaning but questionable schemes of protecting and/or spreading “native” species.
For the biogeographer, therefore, it is very important to know whether or not a plant or animal has arrived at its present habitat by natural forces, unassisted by humans. This may be difficult to determine, but, the problems not withstanding, the distinction between “native” and “alien” (exotic, introduced) has always been very useful. It is at best a relative distinction, however. “Native” plants have become very fashionable of late, and sometimes we forget this relativity, a fact that prompted me several years ago to express some thoughts about the term “native” in an issue of Chinquapin, The Newsletter of the Southern Appalachian Botanical Society (vol. 2, no. 3, 1994). These thoughts, only slightly changed, follow here.
Every plant sowed or transplanted is an alien or exotic, whether or not it is a native species of the region. The very act of transplanting or sowing is an act of manipulation that in some measure, large or small, falsifies the history of plant migration and establishment in the area. In many ways, this kind of transplanting is more insidious than bringing in blatant exotics that clearly stand out. What would appear to be a “natural” dissemination is in fact an artificial one. Why, one might ask, is it more acceptable to play Johnny Appleseed with native introductions than with exotic introductions? The flip side of this is that an alien species can be more “natural” than a native one, if the native plant has been transplanted and the alien species is a longtime naturalized species that has found its way to the new location by unassisted means.
Just what is “native” or “natural,” anyway? Some presumptive aliens have been part of the North American flora for so long that there is no agreement on whether they are native or naturalized. There can be no absolute definition of “native,” and no one will ever be able to create a definitive list of the “native” plants of North America. For starters, the first humans to set foot in North America and the generations of Native Americans to follow did not make lists of what they found. Even with clearly naturalized plants that have been here for many years and have long since been spreading on their own accord, it is debatable whether they should be regarded other than as a part of the contemporary “natural” vegetation.
Is a species that has been transplanted from the same premises, county, or state any more “native” and virtuous in the landscape than a species transplanted from another region of the continent or half a world away? An introduction is an introduction is an introduction, no matter what the source or span of transplant. Those who use native species for landscaping should always be aware that they are concocting artificial landscapes, simulating but not creating natural ones. There may be many virtues in planting truly (i.e., unarguably) native species (e.g., preventing exotic invasions, gene pool preservation), but achieving a genuinely natural landscape is not one of them. However subtle the planting may be, the end result is the same-an introduced flora, hence a disturbed and falsified landscape. A plant, once ex situ, is introduced. Although it may be a locally native species, it no longer is a native plant in the purest sense, even if it has been moved only inches from its original location. Transplanting always falsifies history, however slightly.
Lest I be misunderstood, let me say that I am a strong supporter of preserving native plants unmolested in their native habitats, and this, to me, should be the primary goal of a native plant society. I do not think that such societies should get into the business of transplanting native species on a big scale to protect them ex situ. This only creates botanical gardens, not natural landscapes. Frankly, I think federal, state, and local governments often over-landscape, regardless of the species being used. Native plant societies should be champions of the cause of letting nature be nature.