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Meteors, Space Aliens, and Other Exotic Encounters
Tom Hofacker - USDA Forest Service, Forest Health Protection, Auditors Building, 201 14th Street, S.W. at Independence Ave., S.W., Washington, D.C. 20250
From: Exotic Pests of Eastern Forests, Conference Proceedings - April 8-10, 1997, Nashville, TN, Edited by: Kerry O. Britton, USDA Forest Service & TN Exotic Pest Plant Council
Exotics have had a big impact on our environment. If you
do not think so, just look at how many people believe that humans would
not exist on this planet were it not for exotics. This belief centers on
two main theories: (1) that humans could not have evolved were it not for
a huge meteor from outer space striking the earth resulting in extinction
of the dinasours, the rise of mammals, and the eventual appearance of humans;
and (2) that the development of humans or human ancestors was the result
of intervention by aliens from outer space; certainly, this would have been
the ultimate exotic introduction! In any case, this is the last you will
hear of meteors or space aliens. That is not the kind of exotic encounter
you will hear about during the rest of this conference. The exotics we are
talking about are just alien plants and animals from other continents. Sometimes
though, when I think about what has happened in the past and what we are
faced with in the future, these exotics seem almost as scary (and a lot
more real) than dinasour killing meteors or space aliens.
During this conference, you will hear much about what has happened in
the past when exotics like chustnut blight, white pine blister rust, and
Dutch elm disease were introduced into North America. While American chestnut,
western white pine, and American elm are not truly extinct like the dinosaurs,
they are essentially ecologically extinct in terms of the structure and
function that these trees provided to the forest and urban landscapes that
they once dominated.
Also important are the actions we have taken to deal with exotic introductions:
millions of acres treated with mirex bait to control imported fire ants,
millions of acres sprayed with DDT to control gypsy moth, millions of acres
treated with herbicides to control noxious and exotic weeds. The monetary
cost of these treatments alone have been staggering.
This is all in the past. Let's think about two possible future scenarios:
Future 1 - An exotic fungus is introduced into the southern US.
This fungus causes a disease in loblolly pine that is not as bad as chestnut
blight was to American chestnut or white pine blister rust was to western
white pine. This fungus only kills about 75% of the loblolly pine in the
South. Other southern yellow pine species are also affected, but to a much
lesser extent. What do you think the environmental, social, and economic
effects of such an event would be?
Future 2 - An exotic bark beetle enters the United States. The
beetle is quite small (only 1.5 mm long); it breeds in several species of
maple, but prefers sugar maple. The adults feed in twig and banch crotches
and leaf axils. The beetles have been in the US for 30 years before they
are identified, so they are widely distributed in the eastern US. The beetles
cause no significant tree damage, and are of little concern - until an unusual
number of dead sugar maples are found in New York, New Hampshire, and Vermont.
The beetle is found to be vectoring a new species of fungus that kills 86.5%
of the sugar maples from Maine to Minnesota. Again, what do you think the
environmental, social, and economic effects of such an event would be?
Do you think these scenarios are too unlikely to even consider? If so,
I would like you to think about the globalization of the world economy,
the effect of exponentially increasing world trade, the effect of easy air
travel, and immigration by people who desire to (and do) bring their native
plants into the US along with them, and the effect of trade agreements like
GATT on our government's ability to issue protective regulations.
In order to present a balanced view of the exotics issue, I feel compelled
to point out that not all exotics are "bad." Most of the food
we eat in the US is of exotic origin; many consider having this exotic food
available for people to eat to be "good." Honeybees were imported
into the US by English settlers; these are also "good" (unless
they are Africanized "killer bees"). On the other hand, Spanish
explorers imported horse flies, and stable flies; these are "bad"
because they literally bite us people on the butt. It is also probably important
to remember that perceptions of bugs or fungi or weeds as "good"
or "bad" are value judgments that people make. These perceptions/value
judgments are important because they govern our personal and society's responses
to "opportunities" or "problems."
Ultimately, you will have to make your own value judgments about these
past and future exotic introductions. I hope that I have given you some
things to think about. I do not want to unduly influence you, so, in closing,
I would like to leave you with two thoughts: these exotics are worse than
godawful and we need to do more to deal with them.
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