Re: Introduction

[Paul Krombholz <krombhol at teclink_net>]

I don't think that taking some species from a river and then 
reintroducing them is anything to worry about when our country is 
crawling with all kinds of introduced species.  And even that fact 
gets some people more upset than they need to be.  There is a "rule 
of 10's" that is a rough guide to predicting the fate of an 
introduced species.  Of every 10 introduced, only one will survive, 
and of every 10 that survive, only one will multiply so much as to be 
a concern.

With introduced species that have spread widely or are spreading, the 
genie is definitely out of the bottle and can't be put back in.  The 
only thing we can do is watch and see what happens.  Often it is not 
so bad as originally predicted.  There is a period of evolutionary 
adjustment, both in the introduced species and in the populations of 
other species affected by the introduced species.  Things almost 
always settle down without anybody going extinct.  In the 1920's 
Elodea canadensis got introduced to Great Britain, and for a while it 
looked like it was going to crowd everything out.  Now it is actually 
not that common a plant in rivers. Possibly something tasted it and 
found it good.  Starlings got introduced into America about a century 
ago, and spread rapidly across the continent.  Populations of 
bluebirds and red-headed woodpeckers declined drastically because the 
aggressive starlings out-competed them for nest holes.  Now, bluebird 
and red-headed woodpecker populations have risen, perhaps not quite 
to their original levels, but they are definitely not appearing 
endangered.  Perhaps they have become more aggressive.  Wolves and 
grizzlies have been reintroduced into Yellowstone Nat. Park, and the 
moose mothers had to learn that these guys were dangerous.  After 
losing their calves, they appear to have taken rather effective 
measures to protect their young the next year.

The zebra mussel is spreading with extraordinary rapidity throughout 
the great lakes and our river systems.  It clears plankton out of the 
water so efficiently that it threatens other plankton feeding 
species.  (I wonder if it would be useful in our tanks combating 
green water)  We will just have to wait and see how it all works out. 
Actually, for aquatic plant fans, the zebra mussel is not all bad. 
Lake Erie and tributaries were so eutrophic that huge algae blooms 
shaded out submersed aquatics and Vallisneria was about to be 
declared a threatened species when along came the mussel and cleared 
everything up.  Now, Vallisneria is doing so well that boats can 
hardly get through it.  I'm kind of looking forward to seeing what 
happens when the zebra mussel makes it to the Ross Barnett reservoir. 
The water is too muddy now for much of anything to grow except 
floating plants.  If the mussel can clear up the mud a bit, we might 
have a more interesting submersed flora.


Fire ants have been here in Mississippi for some time, and many local 
ant species have made somewhat of a comeback.  Twenty years ago, fire 
ants used to invade my kitchen.  Now it is the ubiquitous little 
brown sugar ant that will not be discouraged, no matter how many 
thousands of them I kill.  They really run the place around my house. 
My whole front lawn is one vast sugar ant colony.

The killer bees are here.  The brown tree snake is slithering 
northward from Florida.  Climbing ferns are smothering trees. (I 
wonder if we could smother the climbing ferns if we planted lots of 
kudzu in the affected areas.)  There are also monkeys in the trees as 
well as various exotic parrots.  Walking catfish could have walked to 
Canada by now if they could take the cold weather.  Hydrilla and 
Hygrophila polysperma are in a number of southern river systems. 
Even Glossostigma is loose.  Is it going to be a lawn weed in damp 
areas?  Maybe you could one-up the neighbors if you had an all-glosso 
lawn.  I mean your real lawn, not the one in your aquarium. 
Practically every kind of aquarium plant grown in Florida tropical 
fish farms is already loose in Florida.

House finches were taken from their western habitat and introduced 
into the east around 1940.  They have spread over most of the eastern 
U.S. and have already reached their western range.  They are carrying 
with them a nasty eye disease that is frequently fatal.  What can we 
do about it?  Nothing.  We will just have to let natural selection 
take its course.  We have more immediate things to worry about, like 
West Nile disease and SARS.

Out of all the introduced species, the worst one is probably chestnut 
blight.  That one really does appear to be capable of making the 
American chestnut extinct.  Without scientific intervention, it 
probably will.

In the long run, everything will work out.
--
Paul Krombholz in sunny central Mississippi