- [Narrator] At first glance it might seem that
introducing new species
the human act of taking species from somewhere else
and dropping them in a different area,
would be good for biodiversity.
Let's face it, if you take a bunch of beautiful flowers
and plant them in your garden
you're increasing the biodiversity in your garden, right?
You raised the species richness in your garden.
But it's not a simple additive equation.
It's more complicated than that.
The term introduced species is synonymous
with exotic species.
The definition is, any species that through the activities
of humans is knowingly or accidentally transferred
from its native habitat into one in which
it doesn't naturally occur.
An introduced species is the opposite of a native species.
Which is one that occurs in an area naturally.
Without human intervention.
Many introductions are intentional.
We do it on purpose.
And we've been doing that for a heck of a long time.
Probably ever since humans came onto the scene
and realized that they could pick something up
that was alive and bring it somewhere else
to serve their purposes.
From goats and pigs to cattle and crops,
mostly we transport organisms that will do some
good for us through agricultural means.
We've been introducing plants and animals
to places where they weren't native
for a long, long time.
Usually when people think about introduced species
they're really thinking more about the accidental ones.
The things that happen coincidentally
alongside human activities.
When we introduce a species to a new area,
everything that's living on, in, or with that species
comes along with it.
If you pick up a cow from one place
and move it to another,
it's gonna bring along all the parasites
that those cows normally deal with.
I think people immediately picture images
of rats streaming off the ships when they pull into
some beautiful Tahitian paradise.
Or the snakes that came into Guam with military movements
during World War Two.
These animals are legendary in doing damage to native birds.
They're very obvious ways that introduced organisms
radically change biodiversity, in a single place.
There are so many other subtle ways that introductions
happen and cause problems.
The bottom line is that the world economy is hit
with an annual cost of 1.4 trillion dollars
dealing with the negative impacts,
obvious and not so obvious, of introduced species.
That's a number I have a hard time wrapping my mind around.
If you had an extra 1.4 trillion dollars to play around with
there's a lot of possibility to do some good in the world.
Because humans have been introducing new species
for a long time, the concept of native habitat
is a little bit slippery.
The human activities that caused the transfer
can happen long before we recognized
that it actually happened.
So that sometimes the history of an introduction
can be lost.
When we aren't sure of the history,
up until the point we are sure,
or have some reasonable evidence,
we call those species cryptogenic.
Crypto means hidden.
Genic means origin.
Solving the riddles of cryptogenic species
underscores another reason why collections
are so important.
The only way to trace the origins of introductions
is to know what was there beforehand.
Collections can preserve that historical information
and collections made today
establish baselines for future reference.
If those collections are maintained in perpetuity
those baselines are gonna be good 100 years from now.
Or 1,000 years from now,
when we see a radically different and altered environment
due to the introductions.
So we can use collections to try and get answers
to this problem.
Not all species are in fact harmful.
Clearly they're not all harmful to us.
Because the ones that we introduce on purpose
are ones that are there for our benefit.
Some introduced species can provide new food sources
or even habitats for native species.
Native species aren't always helpless and harmed.
They can make use of some of the newcomers.
Introduced grasses and corn for example,
are eaten by native species.
And certain trees that've been introduced
can serve as habitats for birds.
Some introduced species live under our radar,
we don't even know they're there.
Doing little perceivable damage to the ecosystem,
by reducing species richness.
But some introduced species certainly go beyond
just living peacefully, alongside the natives.
They can do this because they have competitive advantages.
They lack natural controls,
such as the predators or diseases that keep them in check
in their native habitats.
Some invasive species are generalists.
Which means they can tolerate, reproduce rapidly,
and thrive in a wide range of environmental conditions.
Allowing them to successfully compete with
and overwhelm native populations.
When introduced species take over an environment
at the expense of native species,
they're known as invasive species.
All invasive species are introduced,
but not all introduced species are invasive.
Here's an example of consequences for humans
as well as for species richness.
In 1992, an introduced species of comb jelly
was found in the Black Sea.
Comb jellies are weird, transparent,
jellyfish-like forms with a voracious appetite
for fish larvae and eggs.
Within months that single introduction resulted in
the total collapse of the anchovie fisherie,
in the Black Sea.
Comb jellies tolerated the conditions in the Black Sea
and their population exploded,
at the expense of the anchovies.
The bottom line here is that introduced species
can out compete the natives for food,
for space,
and other resources.
They alter the ecosystems food webs,
disturbing crucial elements and interactions
that would otherwise contribute
to healthy ecosystem function.
The comb jelly is a good example of that.
Sure, your species list for the Black Sea
is gone up by one, but it destroyed all the anchovies.
You have to take a species off the list.
Plus, perhaps whatever else was eating the anchovies.
And before you know it,
because there's nothing for the comb jellies to eat anymore,
they're gone, too.
So, not only have you not added a species,
but in the end you've actually subtracted a whole bunch.
So invasive species are ultimately,
organisms that cause decreases in ecosystem function.
That's another definition of invasives
that we need to come to grips with.
What's worse, invasives very seldom come by themselves.
As I was saying with the cow example,
they often come with new diseases,
new parasites,
new accompanying effects,
that we can hardly predict.
Another good example of invasives are pathagens.
Something that we don't often consider as invasives.
These include disease-causing organisms like,
fungi, or bacteria, and even viruses.
These are things that we also introduce to wild populations.
And there are extinctions that come from that.
In fact, in the past 500 years we've directly caused
the extinction of more than 100 species of birds,
partly through the introduction of disease
and heck knows what damage we did to organisms
that were depending on those birds.
In the forest realm,
Dutch Elm disease was something that,
when I was growing up was a huge thing
and actually it still is.
In North America, Dutch Elm disease left skelatol trees
for miles and miles.
When I was a kid growing up in Toronto in the '60s
80% of the elms in the city were killed.
And it was really sad.
Those trees were not only gorgeous,
they were very important lumber.
Elm trees were a direct service to us,
in so many different ways,
from producing shade to furniture.
The fungus was introduced by bark beetles,
some of which were native and some of which were introduced.
Both of which supported and co-evolved
with the fungal pathogen.
Which could not be stopped.
This idea of being a generalist,
the ability to reproduce and displace natives,
the ability to become more abundant at the expense
of other species, to introduce diseases,
to proliferate in non-native habitats,
that should sound pretty familiar.
Because that's us.
In some ways, we are the ultimate invasive species.
We don't just introduce ourselves,
we are invasive.
The difference is that unlike the comb jellies
and the bark beetles and cows,
we're capable of recognizing that fact
and maybe mitigating our impact.
We can look at the world and the problems
and start thinking about ways to control the invasives,
to coral them,
maybe to reduce their effects
and not introduce them in the first place.
We have to, not just for moral reasons, I think,
but because ironically, and as we said earlier,
the invasives that we're bringing with us
accidentally or on purpose,
can do a lot of harm to species upon which we depend.
Worse, they can upset healthy ecological functions
upon which all life depends.
Including us.