What is native and does it matter?

Photo: Chrysogonum virginianum, NC 

             native woodland ground cover introduced to Walmer Woodlands

What is a 'native'?

Although our interest in defining 'native' here is focused on plants, the term native can and should refer to all living species that co-evolve to live in any ecosystem.  Ecosystems develop and stabilize when there is an equilibrium of needs and resources and they destablilize and change when the equilibrium is disturbed.  Each species survives because the environment is hospitable to its requirements for life.  That environment includes both animate neighbors and inanimate resources.  All eco-systems are constantly in flux so an equilibrium is actually a time when the fluxes are small and adapting.  Of note is that human activity has been so disruptive to ecosystems that our interventions have become part of the definition of 'non-native'.  Hence, the USDA defines 'native' as the balance of nature that develops over hundreds of years in an ecosystem and the National Wildlife Federation broadens the definition to exclude plants introduced to an area by humans.

Because native species slowly co-evolve with ecosystems over long intervals of time, they often develop complimentary and interdependent relationships with their neighbors.   Darwin described evolution as a process in which natural genetic variation in offspring leads to changes that improves a species chance of survival in its ever-changing environment.   Dr. Karen Pfennig at UNCCH, studies a fascinating and complimentary hypothesis for evolution called hybridization, where two genetically different but compatible individuals produce offspring with advantageous characteristics.  Many Homo sapiens today are having their DNA sequenced and discovering that they carry DNA from Homo neanderthalensis.  

This 'native' issue is currently complicated in today's ever-changing world as we appear to be in midst of the 6th documented mass extinction event, & the first to be engineered by human activity.  Humans therefore not only disrupt ecosystems by introducing non-native species but causing the disappearance, of natives.  This dual impact is likely accelerating changes in native plant populations.  As an example, the USDA recently recategorized the growth zone in Chapel Hill from 7b to 8a.

Are all non-native plants problematic?

Non-native plants don’t necessarily pose a threat to native plants, they are just less likely to support ecosystem health as well as native plants.  They are therefore more likely to perturb the ecosystem.  However, some non-native plants will co-exist in relative harmony and others will actually cause harm to native plants or local ecosystems and these plants are considered invasive.  This isn't always an easy designation as some non-native plants don't become invasive until they have been in an area for years.  There is a nice article by The Prarie Ecologist, which addresses the issues of being a purist vs. a pragmatist about native species.  At Walmer Woodlands, we take a more pragmatic approach.  We support and introduce many NC native plants in our gardens, try to keep natural-occurring invasive plants at bay as much as possible, try to be judicious when introducing non-native plants to our gardens and understand that it is impossible to erase the impact of human activity from our landscapes.  

One could argue that the native / non-native concern is irrelevant.  Evidence suggests that life appeared on the planet shortly after circumstances allowed and it will likely continue to evolve until the circumstances no longer allow it.  It is estimated that changes in our sun will make life inhospitable on our planet in about a billion years.  Given our knowledge of recurrent mass extinction events on earth, this process is likely to occur many more times before the earth becomes inhospitable to life.  From a human perspective, the question is whether we as an intelligent species are wise enough to learn how to live harmoniously on this planet or will we become one of the shortest-lived species.