WE SHOW TOLERANCE FOR SOME INVASIVE SPECIES?
remember a scene I wrote about more than a decade ago when I looked
down from atop a lighthouse known as Piedras Blancas and discovered
why the California coast was noted for its magnificent views.
crashed along rocky shores; enormous elephant seals lounged like giant
slugs on a beach uninhabited by people; and a lush mat of vegetation
stretched for miles around the lighthouse right up to the surf itself.
I thought the scene idyllic. My host, Jeff Lovich of the U.S. Geological
Survey, gave me another perspective. The ocean and seals were natural.
The spreading vegetation was not. The plant covering virtually every
square yard of the peninsula we were on was a despised invasive species,
an exotic introduced from South Africa. During the last several years
the so-called iceplants had covered the landscape, smothering native
wildflowers and shrubs. As pretty as it seemed to me, the iceplant was
not welcome in California.
also known as Hottentot figs, did not find their way to California by
accident. The first plants were brought to the region a century ago
to stabilize soil alongside railroad tracks. The California highway
department planted iceplants beside roadways up until the 1970s. Iceplants
have no natural enemies in California; therefore they spread, uninhibited
by the usual controls that limit plant dispersal. Outcompeting native
plants for water, light, and nutrients, iceplants soon became the dominant
vegetation in many areas.
iceplants exemplify a dilemma. To someone unfamiliar with the origin
of iceplants, the spreading blanket of healthy vegetation might seem
a horticultural dream. The plants are soft and spongy to walk on, have
no thorns or briars, and have pretty flowers. Before I learned that
they were not native and that I was not supposed to like them, the iceplants
seemed the perfect ground cover for a rocky coastline. Upon finding
out that iceplants have been introduced from another continent, should
I change my opinion of them?
government agencies, and conservation societies are currently involved
in programs to deal with introduced species of plants that cause environmental
or economic damage. The U.S. Fish and Wildlife Service set as a priority
the prevention and control of invasive species "that severely impact
the lands and waters of the United States."
of introduced species of plants are alien to North America. Clearly,
we will never be able to control all of them even with the most massive
of government programs. However, most do not cause what is perceived
to be appreciable or recognizable environmental damage. In fact, most
people probably have species from the list growing in their yards.
purist might decree that any plant that did not evolve in North America
but has become established through human introduction does not belong
here. Of course, if we use that standard, we would not have very much
to eat, as most of our agricultural crops are from other continents.
If we accept
that agricultural crops are an exception, should we consider exotic
horticultural flowers, shrubs, and trees, which are cultivated and planted
around the country in appropriate climates, to be a problem? We are
probably several decades too late to try to put any controls on that
aspect of our nation's vegetative makeup. English ivy, Japanese maples,
and Chinese wisteria are here to stay, with the help of plenty of people
who plant them.
To be sure,
we need to have import/export safeguards to keep out of our country
exotic plants that might be uncontrollable and to keep potentially harmful
U.S. plants from being introduced to other parts of the globe. And we
should recognize the impact of such plants as kudzu in the Southeast,
melaleuca in south Florida, and iceplants in California. But most invasive
species should be dealt with on a case-by-case basis without an overall
indictment simply because a species did not originate here. If you think
about it, most of us didn't originate here either.
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