MAKE LIFE INTERESTING
May 15, 2011
types of invasions have occurred along the Mississippi River in recent
times. Unstoppable, ever-rising floodwaters that are invading a region
and know no master will always catch our attention. Residents over thousands
of square miles of floodplain have been at the water's mercy. Once a flood
is recognized as becoming a problem it is often too late to take effective
that being too late does not apply to another type of invader to the region,
one of an entirely different nature. I saw a disquieting photo awhile
back of a man in Mississippi holding an ugly-faced, meat-eating piranha,
a native of the Amazon Basin. The fish is known from tales about "man-eating"
attack behavior on cattle, horses, and humans in the water. Although some
of the stories are overstated, this fish and most others are not something
we want to become established as invasive species in any rivers or lakes
outside their native range.
species is one brought to a region, usually from another continent that
successfully establishes itself. A piranha in a river in North America
means somebody inappropriately released an aquarium pet into a waterway.
As far as I know, piranhas have not become established in any U.S. aquatic
system. But should they do so, a potential man-eating fish in our midst
would quickly get our attention.
made daily to federal and state governments to set controls on one invasive
threat or another. But like a rising river, it may be too late to stop
the flood. New introduced species enter our country and others every day.
Transportation on a global scale is universal by land, air, and sea. Regulations
have been set for importing some plants and animals, but considering the
traffic overload, the controls and enforcement are minimal.
about invasive species is that few generalizations can be made about what
will determine the success or failure of any particular species. The findings
of scientists can be contradictory. For example, three separate research
studies of invasive plants in Great Britain identified certain seed characteristics
that were in common to successful invaders. However, one study revealed
that having large seeds made a plant more likely to be successful. Another
study found that small seeds were the key to success. The third study
concluded that seed size did not matter. So much for making predictions
about which exotic plants will be most likely to populate England.
confusing example from scientific study of invasive species is that of
the Brazilian pepper tree, a plant in the same family as poison ivy and
poison sumac. The tree has become a major pest in southern Florida because
it outcompetes native trees and supplants most varieties. According to
one authority, Floridians had kept Brazilian pepper trees as ornamental
plants for decades with no problems. Then suddenly in the 1980s they began
to grow wild and create environmental havoc. No one had any idea in advance
that they might become a problem. The ecological paradox is that scientists
remain uncertain about whether any guiding ecological principles can be
applied to predicting whether an introduced species will become a dominant
and invasive part of the landscape or simply disappear.
and regulations have been proposed about how we should deal with the present-day
pervasiveness of introduced species. The solutions make politicians uneasy
and biologists do not always agree on what they are. But if we do not
do something, many environments will be changed in ways that are unquestionably
negative from most perspectives.
alongside a flooding river is unhappy about the situation. Even before
flood waters subside, people vow to become more vigilant about future
flood control measures and about rebuilding. Being invaded by river floodwaters
is a process with an ending; the water will eventually go away. The problem
with many invasive species is that they never will. We need to be alert
for the first signs that a new one is about to invade; we certainly don't
want to find that flooded waters are transporting something like piranhas
into new neighborhoods.
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