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Alien plants, also known as exotic or nonnative species, were
intentionally or inadvertently introduced usually, but not always,
by human activity into a region in which they did not evolve.
In North America, plant species are generally described as native
if they occurred here prior to European settlement. Some may
have been introduced for horticultural purposes. Others arrived
accidentally in seed mixes, packaging materials, ship ballast,
and even on the shoes of international travelers. Within the
United States, a plant native to one area may be carried to
another part of the country and be labeled an alien species.
Native species are those that do occur in the region in
which they evolved. They possess characteristics that make them
uniquely adapted to local environmental conditions. Natives
maintain or improve soil fertility, reduce erosion, and often
require less fertilizer and pesticides than alien species.
Invasive alien plants threaten biodiversity. Biodiversity
refers to the variety of all living things and their interconnectedness.
As a general rule, the more biodiverse an ecosystem is, the
healthier it is. Less diverse ecosystems are more fragile and
less resilient in the face of threats like the introduction
of new species. Without natural controls such as insect pests
and competitors, some alien plants easily can become established
in new areas. Once established, the alien plant species can
out-compete and displace the native plant species, disrupting
ecological processes and significantly degrading entire plant
communities.
Take a ride south on I-95 and you will see kudzu, a fast growing
vine that is blanketing the landscape, choking off trees and
dependent wildlife in its path. Here in Fairfax County, invasive
oriental bittersweet grows along I-66 from Arlington to Fairfax.
Mile-a-minute plagues our stream valleys. Garlic mustard threatens
wooded areas. And phragmites runs rampant in wet areas such
as ponds and drainage ditches.
All plants are native to some region and offer a variety of
ecological, economic, and aesthetic benefits. It is only when
a species is out of place that we should become concerned. Like
a wildfire, invasive plants can seriously damage native plant
and animal communities, increase soil erosion and sedimentation,
and interfere with outdoor recreation. However, unlike wildfire
damage, which soon heals, the effects of plant invasions can
be long lasting. As biological pollutants, invasive plant
populations can grow, adapt, multiply, and spread to unmanageable
levels over time.
How can you help? Use native plant species grown from
local stock for conservation and landscaping purposes whenever
possible. If you do use alien plants, avoid highly invasive
species. The Virginia Department of Conservation and Recreation
in partnership with the Virginia Native Plant Society provides
a comprehensive list of plant species native to Virginia.
Learn more at www.dcr.state.va.us/dnh/native.htm.
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