Invasive Species

Humans are responsible, either directly or indirectly, for the introduction of countless species around the world. Sometimes the animals cause no discernable damage. Other times, entire populations or species of native flora or fauna are wiped out. Join us as we find out how and why some of these great invaders came to be where they are today, and what is being done to correct any damage they've caused.


The story of the insidious starling
On March 6, 1890, a man named Eugene Schieffelin walked out to Central Park in New York City with eighty
european starlings in small wooden crates and, quite deliberately, changed the ecology of North America.
Schieffelin, as it happened, was a huge fan of William Shakespeare. His life's dream was that all of the
birds mentioned in Shakespeare's works might someday come to inhabit his city. Why he didn't just move
to Shakespeare's England home town of Stratford-upon-Avon or even London, no one knows.
A single flock of starlings, called a murmuration, can grow to a million or more birds. They can blanket
the sky, and when they descend on a farmer's crop, they are ruinous. They torment native birds,
including the beautiful bluebird, robbing nests and killing fledgelings. Thanks to the 80 birds he released in
1890, along with another 40 he added to injury in April 1891, Schiefferlin is responsible for the presence
of the more than 200 million starlings found in North America today. Jerk.


They just plain got his goat
Franklin Roosevelt established the 900 000 acre Olympic National Park in 1940. Mountain goats had been
introduced to the area some 15 years ealier, having been released with the permission of the U.S.
Forest Service and the Washington Dept. of Fish, Game, and Furs. When the area became a national park,
it fell under the jurisdiction of the National Park Service. The NPS took a very different view of the
mountain goats, partly because of their policy regarding non-indiginous species. It's a very clear-cut
mandate; it reads, in part, "Management of populations of exotic plant and animal species up to and
including eradication, will be undertaken whenever such species threaten park resources."
Mountain goats, like their domesticated cousins, will pretty much eat anything that grows, and that part
of the Olympic mountains has some plants that are very rare and exceedingly delicate. It seemed pretty
clear that the goats were likely to eat some of these rare plants into an untimely oblivion. When the
park service announced it intended to cull the goats, animal rights groups had a field day. They felt
certain that the goats rights to continue to live in the park outweighed the rights of the plants to
continue to live at all. In the end, the goat activists won, and the cloven-hooved interlopers are
still roaming the mountains to this day.


Conquering the world at a snail's pace
In March, 1977, the French government introduced a snail-eating species of snail, Englandina rosea,
from Florida to the island of Moorea in order to control another invading species; the giant African snail,
Achatana achatana, which grows up to 9 inches and voraciously devours vegetation. E. rosea only grows
to a size of 2 1/2 inches, but instead of chowing down on the target African snails they developed a taste
for partula snails, native to the island for around 1 1/2 million years. By 1984 they had eaten every last member
of one of the seven species of partula, and by 1988 they had eaten every single one of the remaining 6
species found on Moorea. It had taken a little more than 10 years for an introduced species to eradicate the natives.
It turns out, however, that they weren't entirely gone. Scientists realized that the first species was extinct, so
they put in a call to save the remaining 6 species by breeding them in zoos. By 1990, thanks to Ulysses S. Seal
and the zoo directors at the St Louis Zoo, in April, 1987, the zoo world created a breeding plan to save
these invertebrate species.
Fortunately for the threatened slimers, a core group of zoos from the United Kingdom (led by the Zoological
Society of London) and the United States developed a management program that worked very well.
The husbandry routine is the same today as it was in the early 1990's. The snails are checked every day
and are fed twice a week. Volunteers clean the snail's homes, feed them, and keep them moist,
all the while tracking their reproduction and growth rates in journals. The volunteer's first task is to check
if the snails are "sticking" to the sides of their enclosures. Sticking snails are happy snails.
Snails are hermaphrodites; each individual bears the organs of both sexes.
In 1966 a young boy smuggled 3 giant African snails into southern Florida, and his grandmother released
them into her garden. Seven years later, more than 18 000 snails were recovered by the state of
Florida. It cost the state over one million dollars and took 10 years to get rid of them.
Who ordered the escargot ... to go?


Africa + perch + pretty flowers = issues
50 years ago nile perch were introduced into lake Victoria in Uganda. These fish decimated 200 species
of native small fish endemic to this region. This has been called the biggest mass extinction of vertebrates
in recent history. The introduced fish brought more fishermen into contact with the native reptile - the Nile
crocodile, and noone thought that was a good idea.
In the 60's in Rwanda a man introduced water hyacinths which made their way downstream to lake
Victoria and by 1989 they hadclogged 80% of the shore line. This made it difficult to get out to open water
to fish so it resulted in smaller catches. Under the suffocating bed of plants, rotting vegetation fouled
drinking water and caused disinery and serious health problems including malaria and parasites.
Apparently noone has learned any lessons about introducing species to control other introduced species...the
control measure for the plants was to spread a south american weevil. Within 5 years the weevils helped
bring the water hyacinths under control. The weevils don't eat African plants but noone knows if they might
change their diet once all their preferred food sources are gone. And the wheels on the bus go round and round.


World trade fuels world travel...for critters
With the globalization of trade we are driving the globalization of species. At any given hour of any
given day at least 7000 species are likely to be in motion travelling across and between oceans
allowing for one or two new invasive species to establish themselves somewhere in the world every day.
For example, 90% of marine life by weight is from somewhere else other than San Fransisco Bay.
It is unprecidented in human history. With the 10% native species hanging on in the sidelines, what
chance do they really have? Movement was slow and rare in the past, but with the advent of ships
and planes, eventually everything will have an opportunity to move everywhere. Species without
borders will mean many fewer species.

Worldwide, invasive species are second only to habitat destruction as the greatest cause of extinction.