TEASE
ALAN ALDA Some time in the 1940s, a brown tree snake
hitched a ride aboard a US Air Force plane in New Guinea,
and it traveled across the Pacific to the island of
Guam. As a result, Guam lost all its native bird life.
On this edition of Scientific American Frontiers, global
attacks by alien species.
ALAN ALDA (NARRATION) The European gypsy moth has been
steadily transforming America's forests, and now the
Asian longhorned beetle could do the same thing. An
African fungus crossed the Atlantic, to cause a damaging
disease in Caribbean coral. And a Caribbean weed is
smothering marine life in the Mediterranean, and it
now threatens the California coast.
ALAN ALDA I'm Alan Alda. Join me now for Alien Invasion.
SHOW INTRO
ALAN ALDA (NARRATION) It's a tranquil scene on the
coast. A couple of guys are diving -- checking out life
on the lagoon floor. People are boating. Actually I
know who that is out there. She's Rachel Woodfield,
a marine biologist, and she's bringing in a bag of that
weed the divers were looking at.
ALAN ALDA Hiya, Rachel.
RACHEL WOODFIELD Hiya.
ALAN ALDA Is that it, there?
RACHEL WOODFIELD This is it right here.
ALAN ALDA (NARRATION) But the weed is not as nice as
it might seem.
ALAN ALDA We're at Agua Hedionda Lagoon, just north
of San Diego on the California coast. The divers out
there are trying to get rid of every last shred of this
stuff that they can find. It's called Caulerpa taxifolia.
It's an invasive weed that has the potential to literally
smother California's native marine life to death. We
know that because it's already killed off thousands
of acres of coastal life in the Mediterranean. Caulerpa
is a classic example of the phenomenon that we're devoting
this entire program to -- alien species.
ALAN ALDA (NARRATION) Remember killer bees? They're
dangerously aggressive African bees, introduced to Brazil
in 1957. Now they've spread north into California and
the southwest, and beekeepers are trying to figure out
how to cope with them. South American fire ants are
another alien. They attack pets and wildlife, and destroy
native plants. Fire ants got to Mobile, Alabama in the
1930s, probably in soil used as ship ballast. Now they're
in 14 states in the Southeast.
ALAN ALDA What they all have in common is that somehow
they've been transported from their home habitat, to
a part of the world where they did not evolve -- where
they are aliens. It's a great thing to be an alien,
because in your new environment there aren't any of
the predators and competitors that you originally evolved
with, that make your life a constant struggle. So you
can really run wild, and grow like crazy, and take over
the place.
ALAN ALDA (NARRATION) Thousands of plants, animals,
insects, fish and microbes have moved around the globe
to become aliens. Almost always it's humans who do the
moving. Asian hydrilla, for example, was first brought
to the US in the '50s as an aquarium plant. Now it clogs
waterways all over the south. People always have carried
things with them, of course -- either by accident or
design. But now with global trade, alien species are
becoming an irresistible force. In the Great Lakes,
many of the most common species are aliens -- including
the notorious European zebra mussel. Most are recent
arrivals. New Zealand now has as many alien plants as
native, around seventeen hundred of each. Hawaii is
the same. It's thought that right now the US has about
seven thousand alien species of all kinds. Is that a
bad thing? Sometimes the cost is obvious. For example,
20% of California is infested with Eurasian yellow starthistle.
It's toxic to horses, and cattle won't walk on it, so
huge areas of rangeland are now useless. But ecologists
argue that the greatest costs are less tangible. When
species get mixed up in this great global exchange,
the sets of plants and animals called ecosystems can
fall apart, and disappear.
ALAN ALDA We're going to look at four alien species
stories from around the world. Among them they display
all the classic ingredients. There's the nineteenth
century Harvard professor who thought he had the key
to a better silkworm. There's the disease that was blown
across the Atlantic to cause havoc in the Caribbean
-- in coral reefs, and maybe among people, as well.
We're going diving in the Mediterranean, to see first
hand the damage that Caulerpa taxifolia can do. And
first, the story of a bird, a snake, and a small island
in the Pacific...
THE SILENCE OF THE BIRDS
ALAN ALDA (NARRATION) This is the National Zoo, in
Washington, DC. I'm heading for the tropical birdhouse,
in the company of Kathy Brader, the keeper. There's
one particular exhibit we're interested in.
KATHY BRADER Now this is our Guam exhibit. And in here
we have our Guam rail and our brown tree snake. He's
curled up on the top. And he is the cause of these guys'
problems on Guam.
ALAN ALDA (NARRATION) On the island of Guam, in the
western Pacific, the forests are eerily silent. Guam
has lost all three of its unique native bird species.
Six other regional species are gone; just three others
are hanging on. This is the culprit.
KATHY BRADER You can see all the different locks and
equipment we have on there to make sure that he cannot
get out.
ALAN ALDA Sometimes they hide a key, you know.
KATHY BRADER Well fortunately I don't think we have
that problem with the snake. And, let's just back up
here a little bit. For us to have him here, we had to
have a special permit. You can only have males. So there's
no chance that if one did get out, they can't reproduce.
Because we don't need this problem here in the United
States, you know on the mainland.
ALAN ALDA (NARRATION) You can be sure that if the brown
tree snake did manage to get out, the Guam rail would
make an easy meal. Guam has no native snakes, so the
birds developed no natural defenses against them. Horatio,
as he's called, doesn't even recognize the nearby snake
as a danger. It's the mealworms that interest Horatio.
KATHY BRADER We use them as a protein supplement but
we also kinda use them as a treat.
ALAN ALDA As a treat? You know no wonder these birds
are extinct.
KATHY BRADER Yeah. Here, Horatio.
ALAN ALDA (NARRATION) Horatio is descended from the
last 21 Guam rails that were brought in from the wild
in the mid-1980s, for captive breeding.
ALAN ALDA Do you hope to reintroduce them?
KATHY BRADER Yes, but there's literally millions of
these snakes. We can't just go and re-release them with
the snakes still being the problem. When we can solve
that problem, is to reintroduce these birds back into
Guam. We want them in the wild.
ANNOUNCER Here in the South Pacific theater, air transport
bucks fog, mountains and Japs in the routine performance
of its duties.
ALAN ALDA (NARRATION) It was the disruption of war
that led to the devastation of most of Guam's wildlife
- birds, bats, flying foxes, and small mammals. The
island was occupied by the Japanese, fought over, and
became an important air transport hub. Sometime in the
1940s, a few brown tree snakes must have stowed away
on flights, maybe from New Guinea or the Solomon Islands,
and made it to Guam - the first snakes ever on the island.
Today, Guam is infested with brown tree snakes, maybe
1 or 2 million of them - up to 20 snakes per acre in
some areas. It's the highest snake density in the world,
and a major nuisance for people. Their bite is only
mildly poisonous - about like a bee sting - but the
snakes short out power lines, they get into buildings,
and attack anything - wildlife, pets, chickens and children
too. Secured in double cages at the National Zoo, there's
a large research collection of brown tree snakes --
including females -- collected in Guam by veterinarian
Don Nichols. He's been bitten maybe half a dozen times.
DON NICHOLS You need to move quickly once they know
you're here, but I'm just gonna grab the snake by the
head and secure the head, which is where all the weapons
are, and then pull him on out. And as you can see, these
are very long and slender, which is adapted for life
in the trees. And if my hand were a tree branch, then
it could actually extend its body out as much as 67%
out into the air. With a lot of snakes that are not
adapted to life in the trees, you can actually grab
them by the tail and hold them up like this. And the
snakes can't get to you if you hold it away from your
body.
ALAN ALDA But this snake can, huh?
DON NICHOLS But this snake has the ability…its muscles
are so strong that it can actually come right back up
like this, and if I were to let go of the head, it could
come up and nail me, or…
ALAN ALDA Or maybe even me.
ALAN ALDA (NARRATION) Guam is still a major hub, so
the fear is the snake could stow away again, and jump
to other snake-free islands, like Saipan or Hawaii.
There are rings of traps around the seaport and airport.
Cargoes are checked constantly. But in spite of the
vigilance, there are leaks. So far the snake has been
caught on eight other Pacific islands, including Hawaii
- where 14 are known to have arrived. One snake was
even caught in Corpus Christi, Texas. It's only a matter
of time before a new population gets established somewhere.
So the search is on for some way to control, even eradicate,
the snakes on Guam. At the National Zoo, Don Nichols
and Elaine Lamirande are working on a radical idea -
find a disease, which just affects snakes. These samples
all came from snakes that died from a virus infection.
Called paramyxovirus, it regularly crops up in captive
snakes, which live close together.
DON NICHOLS This one looks a little rambunctious, so
I'm going to use the snakehook.
ALAN ALDA (NARRATION) Don Nichols had the idea that
paramyxovirus could be made to spread among Guam's dense
snake population. Right now they're seeing how different
strains of virus, sent here from around the world, affect
the brown tree snake. The snake gets a shot of anesthetic,
which takes about 15 minutes to take effect.
DON NICHOLS Good.
ALAN ALDA You're gonna reach in there, right?
DON NICHOLS Give it a few jiggles to make sure there's
no movement -- you can see. I still will make sure I
got control of her head, but she's quite asleep.
ALAN ALDA (NARRATION) Then a dose of one of the paramyxovirus
strains is injected into the snake's windpipe, causing
a pneumonia-like disease within 2 or 3 weeks. Don says
these viruses pose no risks for people, because they're
active only in cold-blooded reptiles. Our high body
temperature kills the virus off.
DON NICHOLS ...let the fluid trickle down into the
lung.
ALAN ALDA (NARRATION) So far they've tested 16 strains
of the virus, looking for one that will kill the snake
only after a delay, so there's time for the infection
to spread to other snakes. There's no getting around
the fact that this project is about killing animals
- figuring out the best way to give them a really bad
case of pneumonia. That's something that an animal lover
like Don is acutely aware of, but for him it's the lesser
of two evils.
ALAN ALDA How do you answer somebody who questions
whether or not you're being cruel to them?
DON NICHOLS Well, I mean, it's all a matter of your
priorities and I'm the first person to admit... I actually
like snakes, and I like them where they belong. But
these things are a pest species in an area and they
are causing all kinds of havoc. They 're threatening
other islands. And it may not be the most humane way
to kill them, but it's the only way you can do it on
a broad scale.
ALAN ALDA (NARRATION) There was an attempt on Guam
to persuade people to eat the snakes. It never caught
on, and anyway no approach involving catching individual
snakes is going to make a dent in a population of millions.
Don is convinced that only a biological control agent
that can perpetuate itself, like a disease or a parasite,
could have much effect. But could biological control
carry its own risks?
ALAN ALDA Don't viruses reproduce rapidly? Don't they
have a chance to mutate and attack other species eventually?
DON NICHOLS My biggest concern would be whether or
not it could adapt, mutate and adapt to the native lizards.
ALAN ALDA (NARRATION) Don says that paramyxovirus has
never been known to jump to lizards, and of course they'll
do tests before any virus release. But biological control
inevitably carries risks - and that's a measure of how
difficult it is to tackle the problems created by alien
species.
ALAN ALDA The original problem occurred when some snakes
got on airplanes and flew to Guam. Now if you infect
the snakes in Guam, and an infected snake gets on an
airplane and flies to some country where that virus
could hurt those snakes, isn't that a danger?
DON NICHOLS There is a chance of that happening. However,
one of the key things is that these viral diseases are
very density dependant. In other words, high populations,
dense populations -- easy for the viruses to spread
around. But, in the native range of these things, it's
very difficult to find the snakes. They're in very low
density, so... It's not a zero percent chance, I'm not
saying…
ALAN ALDA No, no, I mean, my mind is racing because
it just seems to me that every time we do something
to fix something that we did wrong 50 years ago, we
create a new problem for somebody 50 years from now.
ALAN ALDA (NARRATION) The hope, of course, is that
we've learned how not to create new problems. If the
virus project is approved, the small island of Rota,
35 miles north of Guam, may hold the best hope for the
return of Guam's wildlife. It's still free of snakes,
so there are birds here that are extinct on Guam. Over
the last few years, more than 200 Guam rails, bred in
zoos from the 21 birds captured in the 1980s, have been
released here. MAN Two zero eight five.
ALAN ALDA (NARRATION) They're breeding successfully,
so they can provide a wild nucleus from which Guam itself
can be repopulated -- if Don Nichols' virus works. Guam's
wildlife can never be fully restored, but without snakes
it can return to something like the balance that once
existed. And at the same time, the threat of similar
devastation spreading to other islands can be averted.
GREEN INVADER
ALAN ALDA How long have you been studying this Caulerpa?
ALEX MEINESZ More than 10 years.
ALAN ALDA 10 years.
ALEX MEINESZ 10 years now, yes.
ALAN ALDA (NARRATION) We're in a small town just down
the coast from Nice, in the south of France. Alex Meinesz,
a biology professor from Nice University, is taking
me out fishing.
ALAN ALDA ... in those ten years, how much has it increased?
ALAN ALDA (NARRATION) As with thousands of places like
it around the Mediterranean Sea, this town depends on
a mix of fishing and tourism for its livelihood.
ALEX MEINESZ Yes. On peut monter?
ALAN ALDA Okay, thanks. Bonjour! FISHERMAN Bonjour!
Patrick.
ALAN ALDA Patrick, Alan.
ALEX MEINESZ Alex. Bonjour!
ALAN ALDA (NARRATION) We're on the Vergé family boat.
The waters around here have been fished for generations.
Until now, that is. They don't fish here any more. We
had to persuade them to set their net out last night,
just so we could film the result. And the result is
this.
ALEX MEINESZ Caulerpa
ALAN ALDA Yeah.
ALEX MEINESZ Caulerpa.
ALEX MEINESZ Look. Oui, oui. On arrêt un peu, uh? Look.
And this caulerpa clogs the nets and the fish see the
nets and there is no fishes.
ALAN ALDA Oh, I see. So it hurts fishing just because…
ALEX MEINESZ They see the nets.
ALAN ALDA …it calls attention to the nets.
ALEX MEINESZ Yes.
ALAN ALDA (NARRATION) The weed, called Caulerpa taxifolia,
doesn't belong here. It's a tropical plant, common in
the Caribbean and other warm waters. The northern Mediterranean
gets cold in the winter, but somehow the Caulerpa is
surviving, and thriving - nothing can touch it.
ALEX MEINESZ When you broke it, there comes a kind
of juice out of it, you see?
ALAN ALDA Does that juice have anything in it that
keeps away predators?
ALEX MEINESZ Yes, absolutely. That are terpanes, caulerpanines.
And this is a kind of toxic matter and a repellent matter.
So the fish don't eat it.
ALAN ALDA So it repels fish. So in this area nothing
is a natural predator.
ALEX MEINESZ No! You see all the leaves are entire.
Nothing…
ALAN ALDA Nothing has been eating it!
ALEX MEINESZ No, no eating trace.
ALAN ALDA Yeah.
ALEX MEINESZ On y va?
ALAN ALDA On y va. Holy moly! He really jumps in!
ALAN ALDA (NARRATION) Alex took us into the shallow
water near the town's bathing beach. Everything below
was covered by the Caulerpa - rocks, sand, mud. There's
nothing else down here, no other plants, barely a fish.
It's a classic example of an alien that just takes over
- like the brown tree snake in Guam. Nothing eats it,
and nothing competes with it.
ALEX MEINESZ It's full, uh?
ALAN ALDA Yeah, there's a lot of it down there.
ALEX MEINESZ All the bottom is covered, eh?
ALAN ALDA There's a lot there!
ALEX MEINESZ All the bottom is covered.
ALAN ALDA (NARRATION) The Caulerpa arrived here about
nine years ago. Advancing at an inch a day, it has ruined
the fishing and it'll soon clog the town beach. It's
the same disastrous story, spread out along 1,000 miles
of Mediterranean coast. Caulerpa is easily spread. It's
carried along in fishing nets, and there are millions
of small boats in the Mediterranean - all with anchors.
ALEX MEINESZ A little piece like this, I put this in
the water, after 6 months you have 3 square meters,
with this little piece.
ALAN ALDA Any part of this?
ALEX MEINESZ Any part. Any part.
ALAN ALDA (NARRATION) With its rapid spread from fragments,
and its cold water survival, Caulerpa in the Mediterranean
is behaving in ways that shocked marine plant experts
like Alex. After years of investigation, Alex is pretty
certain he knows how this disaster happened. This is
the aquarium at the famous Monaco Oceanographic Museum,
where Jacques Cousteau was once director. In the early
1980s the Museum, along with several other European
aquaria, started using a decorative, and easy to grow,
plant in their tropical tanks. The plant was Caulerpa
taxifolia. It's still used here today, as it is around
the world. Alex believes that somehow some fragments
of Caulerpa were released from the tanks into the sea.
A museum diver first saw Caulerpa right outside the
building, on the bottom, in 1984. It covered just one
square yard. By 1989, when Alex first saw it, it covered
2 acres. By 1990 it was at nearby Cap Martin, next year
Toulon, 100 miles away, and now it's found from Spain
to Croatia. With no natural enemies to hold it back,
the Caulerpa has been steadily smothering Mediterranean
sea life. In the shallow areas, there's normally a complex
community of over a thousand different species -- algae,
shellfish, worms and fishes, all based on meadows of
native sea grass. In the darker depths there's a different
balance, with the grass giving way to red sea fans.
This is the steep, 100-foot rock wall off Cap Martin,
once a favorite spot for scuba divers. The film is from
1996, shot as the Caulerpa was taking hold. Alex has
been diving here every year since the Caulerpa arrived.
As the alien plant advances, it blocks light out --
from the red sea fans, for example, which die off. Alex
has seen the same process repeated all over the rock
wall. Did this all originate with the Monaco aquarium?
Genetic analysis has shown the Caulerpa is a mutant
strain, unique to aquariums -- including Monaco -- and
not found in the wild. But we'll never know for sure
how it first got loose. In the summer of 1999, our underwater
cameraman swam down the rock wall at Cap Martin to record
the progress of the Caulerpa. The wall is now completely
covered. The last sea fans are dying. The wall is essentially
a biological desert. Once again we're looking at Caulerpa
growing in an aquarium. But there's something else -
it's a kind of slug, and it's eating the weed. The result
- all over the tank, ghostly white fronds of weed, with
their toxic juice sucked right out by the slugs. The
slugs are being studied in his lab at the University
of Nice by Alex Meinesz. In his view, they represent
the single best hope for controlling Caulerpa taxofolia
in the Mediterranean. We've jumped 4,000 miles across
the Atlantic to the Indian River in Florida. Alex's
slugs came from here, collected by Cecelia Miles, a
marine biologist from Florida State University. Here
Caulerpa is eaten -- and controlled -- by the highly
specialized slugs, as it is further south all over the
Caribbean. The hope is that slugs from Florida -- the
northern extreme of their range - might be hardy enough
to survive the Mediterranean winter. In the summer of
'99, Cecilia collected and packed a batch of Florida
slugs for shipment to Alex in Nice. The slugs had their
own air supply for the flight, and were escorted across
the Atlantic by a French grad student.
GRADUATE STUDENT And I see you when I get back. See
you Cecilia. Bye bye.
ALAN ALDA Here you were a student of caulerpa and all
of a sudden it shows up on your doorstep…
ALAN ALDA (NARRATION) Alex has been studying different
slugs for years. The Florida batch had been in residence
at Nice University for about 2 weeks when I visited.
His work with slugs and Caulerpa is done on a shoestring
budget, in a makeshift lab behind the biology building.
The Monaco Aquarium connection makes this a very political
subject, so research grants have been hard to come by.
ALAN ALDA …so you've got a chance to see who's working
out.
ALEX MEINESZ Yes. Come in, please. Come in.
ALAN ALDA So they're in there, I don't see any slugs.
ALEX MEINESZ Yes, here.
ALAN ALDA Oh yeah. yeah, yeah! Now is he eating now?
ALEX MEINESZ Yes, I think so, yes.
ALAN ALDA So these slugs really like that toxic stuff.
ALEX MEINESZ Yes. They need the toxic, because they
take the toxins and they stock it in them and then the
fishes doesn't eat it.
ALAN ALDA Oh, I see. So the slugs use the toxins to
keep the fish away from them!
ALEX MEINESZ Exactly. Exactly. Exactly.
ALAN ALDA (NARRATION) The slugs have other highly specific
adaptations to Caulerpa - they need Caulerpa cells as
part of their own metabolism, and they have a special
tooth, which matches only Caulerpa cell structure. Alex
argues that the slugs are so exquisitely adapted to
their one food that releasing them into the Mediterranean
to control the invasion biologically would present a
very low risk. I asked him about it.
ALAN ALDA How do we know the slugs that you bring in
won't adapt and find some other way to live in addition
to caulerpa?
ALEX MEINESZ When the slug have no more caulerpa, they
can not, in one generation say, Ah, we shall change
our tooth, our mouth, our toxin, to eat other things.
You understand? You understand?
ALAN ALDA That takes a lot of plastic surgery!
ALEX MEINESZ You understand?
ALAN ALDA Sure, sure!
ALEX MEINESZ When there is Caulerpa, they eat Caulerpa.
No problem, no problem. When they see there is no more
caulerpa, it is too late. It's too late.
ALAN ALDA (NARRATION) Alex's slugs may be the only
way to go. All kinds of non-biological control methods
have been tried - like releasing poisonous copper from
underwater electrodes… Or simply scraping the weed off…
Vacuuming it up… Freezing it with dry ice… Scalding
it with hot water… Or cutting off its sunlight. But
there's nothing that's practical on a large scale, except
the slugs. I asked Alex again, Is it really smart to
release the slugs into such a paradise of food?
ALAN ALDA All of a sudden, they're dining out every
night. They're going to Maxim's every night. And they're
doing pretty well. Now, you're liable to have some pretty
fat, happy, healthy slugs around looking for trouble.
ALEX MEINESZ No, no. You have a prairie of Caulerpa
with many slugs in it and then they control the caulerpa
and it is finished, that we think. But what you want?
Do you want to have a Mediterranean Sea full with caulerpa
without any control method? We must have a predator
for this invader. Without predator, the Caulerpa --
that is a risk that we see now. We can see, you have
see it when we snorkeled. You see with the fisherman.
It covered all the bottom and it expands every year.
So what do we do? Do we do nothing? Or do we try this?
ALAN ALDA If you can't get rid of it, if the slugs
don't work, if the slugs are too dangerous, if the slugs
work but governments won't let you use the slugs, what
will the Caulerpa do? What will happen to the Mediterranean?
ALEX MEINESZ What happens is exactly the same that
happened since ten years. It extends. It extends every
year, in new country, new regions. And we think that
this algae is able to colonize most of the region of
all the Mediterranean Sea.
ALAN ALDA (NARRATION) Now fast forward two years and
7,000 miles. We're back at the California lagoon where
we began this program. Just like in France, the alien
Caulerpa here is untouched by any natural enemy. It's
capable of smothering the native eelgrass. The patch
of bright green Caulerpa was first noticed in 2000,
suspiciously close to a storm drain outlet. Caulerpa
is widely used in home aquariums, so someone probably
dumped one out into a drain somewhere in the area. Getting
rid of the Caulerpa here, and in one more spot near
Los Angeles, is now the responsibility of Rachel Woodfield,
who works for an environmental consulting firm.
ALAN ALDA Where did you first find Caulerpa around
here?
RACHEL WOODFIELD The first place we found it was right
out here in the eelgrass beds. We were monitoring the
success of the native eelgrass beds and came across
this bright green terror growing in there. We weren't
sure what it was at first. We've all heard of Caulerpa
in the Mediterranean. But to make the relation that
this is the killer algae. It took us a little while
to figure it out.
ALAN ALDA Was it widespread by the time you first discovered
it?
RACHEL WOODFIELD It had spread throughout this small
harbor area. It covers about five acres. So we built
this boom around it to keep all the boats out and people
who might want to come in and see it, and might potentially
spread it.
ALAN ALDA (NARRATION) They decided to try killing off
the Caulerpa a few square feet at a time - something
it's too late for in the Mediterranean. Portable frames
are covered with plastic tarps, which are sealed to
the lagoon floor with sandbags. The underwater tent
is then given a dose of chlorine and left for a few
days. Everything inside is killed - Caulerpa and native
eelgrass - but so long as they get all the Caulerpa,
only eelgrass will grow back. After a year, it seems
to be working.
RACHEL WOODFIELD We're at a manageable point right
now. We have two infestations. They're deep back inland
in lagoons. There's calm water. We're able to have the
luxury to put these tarps down and deal with it, and
keep an eye out for it before it gets offshore.
ALAN ALDA Is this the major threat or the only threat
right now from an alien species in this, in these waters?
RACHEL WOODFIELD This certainly is not the first exotic
species that this lagoon has seen. However, this is
the first species that really has the potential to cause
some serious, serious harm to our coastline and that
is at a state that is manageable.
THE SILKEN TREE EATERS
ALAN ALDA (NARRATION) We're in the New York City borough
of Queens, to witness the death of a tree. One of the
cemetery's prized mature maples is coming down. It was
doomed anyway, and this is why.
JOSEPH GITTLEMAN What we have here is larval Asian
longhorned beetle. And if we just pull him out of here,
you can see they're quite sizable. They have large mandibles
well suited for the environment inside a log and chewing
its way through the hardwood.
ALAN ALDA (NARRATION) The Asian longhorned beetle is
as big a threat to America's forests as Caulerpa is
to our marine life. In late summer, each female distributes
a couple of hundred eggs around several trees. The beetles
arrived in the mid-1980s, in wooden packing materials
from China - so as usual with alien species, they have
no natural enemies here. Right now they're just confined
to the New York City and Chicago areas, but already
seventy five hundred trees have had to be destroyed.
The damage is done in the spring, when the larvae hatch
and eat their way out, emerging as adult beetles to
begin the cycle again. The tree cannot survive the process.
JOSEPH GITTLEMAN You don't see much on the outside
sometimes and then when you flip it, you see what type
of damage this is capable of. Our goal is total eradication
of this insect from North America.
ALAN ALDA (NARRATION) Eradication means cutting up
every infected tree, picking out the larvae, chipping
the remains and burning the chips. And then every apparently
healthy tree within 700 feet gets a dose of systemic
insecticide, just in case there are larvae inside. Like
with Caulerpa, we still have a shot at halting this
alien invasion. The dominant hardwood in the eastern
American forests was once chestnut, until it was almost
wiped out by chestnut blight - a fungus from Japan -
in the 1880s. As a result oaks took over, but they're
being devastated by the gypsy moth - from Europe. So
now maples are coming to predominate. But they're one
of the favorite foods of the Asian longhorned beetle.
It would be the worst ever pest of American forests.
JOSEPH GITTLEMAN It's a pest of about 18 different
species of hardwood trees in the northeast forest, including
all of your maples, your elms, horse chestnuts, willows,
poplars, birch, ash trees. So your talking about a sizable
percentage of the natural forest in the northeast. And
the possibility of spread outside of the, if you would,
the ornamental situation now, from a backyard pest to
a forest pest would be catastrophic.
ALAN ALDA (NARRATION) Many people in the northeast
have first-hand experience of a continuing forest catastrophe.
The gypsy moth regularly defoliates and kills large
swaths of oak forest, in an ever-expanding area. It's
costly and destructive, it leads to large-scale pesticide
use, and it's plain disgusting, too. The gypsy moth
has been a classic story of alien invasion for over
a hundred years. This film was made 50 years after Etienne
Trouvelot, a Harvard astronomer, had accidentally released
a group of gypsy moths from his home in Medford, a Boston
suburb. He'd imported the moths from Europe in the hope
of establishing an American silk industry. The first
big defoliation took place in Medford in 1880, 10 years
after the release. There were more or less constant
attempts to prevent the moth from spreading, including
extensive use of toxic lead arsenate sprays. But by
the late 1920s it infested 40,000 square miles of New
England, New York and Canada. Victory was declared several
times, but the gypsy moth proved unstoppable. Today
it's all over the northeast, and still on the move.
From this lab on Cape Cod, the USDA continues to battle
the gypsy moth, as they have for a hundred years. Inside
labs sealed with airlocks, they keep gypsy moths and
about 40 other aliens which might be the next invader.
They even have some Asian longhorned beetles here. They're
determined not to be caught off guard again.
VIC MASTRO The gypsy moth is fully entrenched in the
United States. We will never eradicate it. The goal
now is to slow that natural spread. You can eliminate
some pesticide use, save some dollars by not letting
uninfested areas become infested sooner than they would
naturally.
ALAN ALDA (NARRATION) Historically, the gypsy moth
spread westward at about 13 miles a year. In the last
few years, that's been slowed to about 5 miles a year,
with a program that's like a military campaign. They've
managed to tap into the enemy's signaling system - the
chemical pheromone which the darker male moths follow
to lead them to the females. USDA researchers first
isolated the pheromone from female moths about 30 years
ago. Then a synthetic version was developed. It's contained
in this little plastic tube at the head of the wind
tunnel. It's a powerful attractant for any male moth
that's downwind. Each spring, to detect where the moths
are, half a million pheromone-baited traps are set out
along the front line, from Wisconsin to North Carolina,
and also throughout the western US. So now it's possible
to concentrate attacks in the right place the following
year, before infestations build up. This couldn't be
done before. Today the insecticides are much less toxic,
too, although they do kill other insects. Right from
the start, people tried biological control against gypsy
moths. It was understood that alien species are successful
because they have escaped their natural enemies back
home. So it seemed obvious that importing some of those
enemies would be beneficial. A Massachusetts state lab
was set up to breed and distribute many different predatory
beetles and flies, and some diseases, brought in from
Europe or Asia. Nothing was very successful, and it's
turned out to be a classic lesson in how not to do biological
control.
VIC MASTRO With gypsy moth about 40 or 50 exotics were
introduced, but only about 12 of those were established.
Some of those are not specific to gypsy moth and that's
caused a problem.
ALAN ALDA (NARRATION) The most notorious example is
this little fly, called compsilura, brought in from
Italy. In a series of rapid, darting attacks, it plants
its eggs inside gypsy moth caterpillars. Eventually
the eggs will hatch into a maggot, leading to a gruesome
death for the caterpillar.
VIC MASTRO Compsilura's range now extends all the way
across the United States, so it's far out distanced
the gypsy moth. And it attacks native species throughout
that range.
ALAN ALDA (NARRATION) Compsilura turned out to be more
interested in attacking native caterpillars than gypsy
moths. As a result some of our most spectacular native
moths are greatly reduced in numbers and probably extinct
in some areas. The lesson we've learned is that biological
control agents must be absolutely specific to the particular
pest. They've taken the lesson to heart back at the
Cape Cod lab. These are gypsy moth eggs, being spread
onto a nutrient base. It's the production system for
the latest biological control agent - a virus. When
the eggs hatch, in 180 days, the cups are infected with
the virus. With this timing, the virus will kill the
gypsy moth caterpillars just as they reach maximum size.
It's the most efficient way to produce the largest amount
of virus, which is now being used in aerial spraying.
The virus occurs naturally, it was isolated from gypsy
moths already in the US, and it's supposed to only attack
gypsy moths. The problem is it's expensive, because
it can only be produced using live gypsy moth colonies.
With our century-long struggle against the gypsy moth,
it's clear that it's better to prevent alien species
than try to cure them. But Vic Mastro believes the task
is so enormous that our only hope lies in knowing ahead
of time where the dangers are.
VIC MASTRO I think the problem of introduced pests
is a huge problem. I think it is as big a problem as
global warming. I don't think we can exclude everything.
It's just a huge, huge task. And the volume of people
moving around the world and trade items is so great
that you can't look at everything. But I think we can
target very specific things and say we'll exclude those
from introductions.
ALAN ALDA (NARRATION) And right now, we're faced with
two certain targets for exclusion. Caulerpa taxifolia
and the Asian longhorned beetle are both potential gypsy
moths, or worse. And in both cases, there's still time
for an ounce of prevention
DUST BUSTING
ALAN ALDA (NARRATION) The Virgin Islands. From here
down to Venezuela it's a five hundred-mile loop of beautiful,
small islands set in a sparkling sea. They're some of
the world's most popular tourist destinations -- to
find the sun... or catch a wave. Below the surface things
get even better. Coral reefs -- the rain forests of
the ocean -- delight the eye and the imagination. But
here they are the setting for a most surprising alien
invasion. It's a coral disease, which came from another
continent, and a completely different environment. In
the winter of 1998, I found myself being thrown around
in a small boat, in the company of three coral experts
-- Gene Shinn and Ginger Garrison of the US Geological
Survey... And Garriet Smith from the University of South
Carolina. We're off St. John -- but this is no vacation.
ALAN ALDA Caribbean, they said, we're going to shoot
in the Caribbean. Nice. All these great stories, sun,
surf...
ALAN ALDA (NARRATION) We found a spot that was sheltered
and got ready to check out the reef. The scientists
and I are going to be free diving, while our underwater
camera crew will be using scuba. Free diving's a lot
simpler than scuba, and just fine for seeing shallow
reefs like these, ten or twenty feet deep. The bad weather
has stirred up sediment, so it's not as clear as it
could be. But it's more than enough for Ginger to point
out the problems. Here comes the free dive... And here's
the problem. On this boulder coral, large patches --
called "white plague" -- where the living surface has
died off.
GINGER GARRISON Looking pretty slick there.
ALAN ALDA (NARRATION) As we head back down, I realize
that white patches of different sizes are everywhere
on the boulder coral. It's one of the Caribbean's principle
reef-building corals, so this is a disturbing sight,
to say the least.
ALAN ALDA When I see the white stuff down there, what
am I looking at?
GINGER GARRISON Well, the white area that's surrounded
by the normal looking coral tissue that's brown is actually
just the skeleton. What's happened is the disease, whatever
the pathogen is, has evidently killed the polyp and
that tissue has sloughed off. So it's as if we lost
everything except our bones so that we wouldn't have
any flesh on them.
ALAN ALDA (NARRATION) Next Ginger takes me down to
check out the sea fans. There are clumps of them all
around, waving lazily in the swells. Sea fans are one
of the soft corals -- not reef-builders, but an important
part of reef ecology, providing shelter for many inhabitants.
But the sea fans are in bad shape. This is a typical
example -- chunks of the fan rotted away, with bright
purple patches. Once you know the symptoms you notice
them everywhere. Garriet Smith outlines a light purple
infected area. Eventually it'll die off, leaving a gaping
hole in the fan. Here the process has already started.
This is not just a local problem -- sea fans all over
the Caribbean are affected. On the reef there are fans
at every stage of deterioration. This one's lost almost
all its living tissue. So out we came -- cold, wet,
tired, depressed at the state of the reef. And as if
that weren't enough...
ALAN ALDA I have a blister from my flipper.
ALAN ALDA (NARRATION) Then I realized that my companions
don't care about working conditions. It's knowledge
they're after.
ALAN ALDA Ha ha ha, I love it. Science!
ALAN ALDA (NARRATION) This is a diseased Caribbean
sea fan in Garriet Smith's lab at the University of
South Carolina. You can see the skeleton from which
the living white tissue has died back. The brown growth
is some kind of secondary infection, and the purple
is an immune reaction that shows the coral is trying
to fight whatever is attacking it. So what is attacking
it? The team's now pretty certain they've nailed it
down. Here's what they did. Samples were taken from
diseased sea fans from six different islands. After
culturing for a few days, this is what they got... A
whole mix of about a dozen fungi and bacteria. It looked
to Garriet that only one was common to all the sea fans.
It had the typical threadlike appearance of a fungus.
Garriet confirmed that it caused the disease, by deliberately
infecting healthy sea fans. So now it was time to identify
the fungus. It's routine nowadays to map out the DNA
of organisms.
KIM RITCHIE A - G - T - A - A...
ALAN ALDA (NARRATION) Garriet and Kim Ritchie mapped
out the fungus' DNA, looked it up in the databases --
and got a big surprise. Sea fan disease was caused by
a common soil fungus called Aspergillus. You could find
it in any backyard. But how was Aspergillus getting
to coral reefs in the Caribbean? Take a look at this.
This picture was shot from the space shuttle over the
Atlantic. The brown stain is dust -- millions of tons
of it -- coming from new farmland in Africa. In drought
years, when there are often dust-bowl conditions, huge
quantities are swept across the ocean on the trade winds,
to settle on the Caribbean. Gene Shinn suspected that
the dust could be delivering a constant dose of damaging
material to the water, and to the coral. And it could
explain why coral diseases appear all over the Caribbean
at the same time. Gene takes up the story.
