Exotic Plant and Animal Invaders
Air Date: Week of November 20, 1998
Plants and animals which get imported from other locations, known as "exotics," can sometimes dominate new ecosystems that do not have the necessary predators, or other checks and balances, in place to protect against them. Invader species can threaten biodiversity by killing off the other species in their path. Chris Bright of the World Watch Institute, has written a new book called "Life Out of Bounds: Bioinvasion in a Borderless World." Steve Curwood speaks with Mr. Bright about how contemporary travel and technology have increased the odds of such exchange and contact.
CURWOOD: It's Living on Earth. I'm Steve Curwood. From acacia trees to zebra mussels, plant and animal species are turning up far from home, often with disastrous effects for the local ecology. Known as exotics, these immigrant species can invade and dominate their new environments. Among the current threats to the planet's biodiversity, exotics are second only to habitat loss. And they cost US farmers alone about $4 billion a year. The spread of exotics has long been ignored, but efforts to control them now are gaining momentum. The White House is expected to issue an Executive Order soon to coordinate control efforts. Chris Bright of the World Watch Institute has written a new book called Life Out of Bounds: Bioinvasion in a Borderless World. He says our global economy is a big part of the problem. In particular, the 29,000 cargo ships that cris-cross the oceans every day.
BRIGHT: When a ship fills its ballast tanks in one port, it tends to suck in all sorts of organisms that might be swimming in the water nearby or in the sediment and mud and so forth. and then when it moves to another port, it may pump a lot of the water out. And it obviously injects those organisms back out into this new realm. And it's almost as if we have a set of artificial currents that now encircle the globe and that overlay the natural currents, but these artificial currents are much more efficient at moving small creatures around than are the natural currents.
CURWOOD: Now, Chris, you call the invasion of exotic species "smart pollution." What do you mean by that?
BRIGHT: The distinction I'm aiming at is, it's got to do with the difference between chemical pollution and the way living things behave. You know, chemicals are just, they're basically inert. You put them out there and they just sit there. Living things don't do that. They can multiply. They do multiply. And they can adapt. They can get better at exploiting a new range, the resources in a new range, and at suppressing the native occupants of that range.
CURWOOD: Are there certain characteristics that make for a good exotic? I mean, rapid reproduction, you know, weediness, whether it's a plant or if it's something that, you know, insects or certain rodents can do, would obviously give an organism a leg up in any environment, right?
BRIGHT: Right. But weediness doesn't predict categorically. The sea lamprey in the Great Lakes, for instance, is a highly-specialized kind of predator. I call it a fish vampire, you know, it attaches itself to the side of other fish and drinks their blood. It's a very dangerous exotic in the Great Lakes, but it's not really a weed.
CURWOOD: I have a list here of just a few examples of exotics in this country.
BRIGHT: Uh huh.
CURWOOD: It's amazing. Some of these are obvious. But tell us about some of the non-native species here in North America that people might be surprised to find out are exotic.
BRIGHT: Where I lived in northern Virginia, the biome that I know best, the sort of mid-Atlantic broad-leaf forest is just clogged with exotic plants. And I think a lot of people don't realize when they look at it, that they're not looking at something that's really natural. We've got Japanese honeysuckle, which is a highly invasive vine. We've got kudzu, which is another aggressive East Asian vine. White mulberry, Norway maple, barberry and so on and so on.
CURWOOD: Well, look, okay. Bioinvasions have been happening ever since the wind started blowing, right? I mean, one seed would blow to another spot. What's the problem now? Why so much attention on this issue?
BRIGHT: Well, the rates of invasion are now so far beyond what we would regard as the sort of normal background rate, that for all practical purposes we're looking at a phenomenon that is really qualitatively different from what would occur under a purely natural regime.
CURWOOD: What about those exotic species which are introduced on purpose? I mean, how do you make people aware of the fact that they might well be disrupting their own local ecosystem?
BRIGHT: One very peculiar aspect of this problem is that there are a number of industries that are actually very small in terms of their economic size, but that are having an enormous ecological effect through their role in promoting invasions. And gardening is a good example of this. More than 60%, I believe it is, of this country's -- the worst weeds of natural areas are still being sold and planted by the nursery industry. Purple loosestrife, for example, is a good example of that. Purple loosestrife dominates something like 1.5 million acres of North American wetland, and suppresses the native cover. Basically just converts it to the equivalent of a parking lot in terms of its forage value, you know, for wildlife.
CURWOOD: Really. It's so pretty, the purple loosestrife is so lovely.
BRIGHT: Yes, it's beautiful. That's -- one of the difficulties of dealing with invasion is that the results aren't necessarily ugly. Some invasions are really very beautiful, and purple loosestrife is a good example of that.
CURWOOD: Okay. So now we know what the problem is and where it's coming from. But how do we deal with this? I mean, what about ordinary individuals?
BRIGHT: The single most important thing, I think, that ordinary people can do, is to get familiar with the landscapes that matter to them, whatever the landscape or seascape is. And to try to understand what is native to it, what belongs in it and what does not. I call that the development of ecological literacy. I think that as people become more ecologically literate, they're much less likely to tolerate disturbance, whether it's an invasion or other forms of environmental degradation in the landscape.
CURWOOD: Chris Bright is a research associate at the World Watch Institute in Washington. His new book is called Life Out of Bounds: Bioinvasion in a Borderless World. Thanks for taking this time with us.
BRIGHT: Thank you for having me.
Living on Earth wants to hear from you!
P.O. Box 990007
Boston, MA, USA 02199
Newsletter [Click here]
Donate to Living on Earth!
Living on Earth is an independent media program and relies entirely on contributions from listeners and institutions supporting public service. Please donate now to preserve an independent environmental voice.
Sailors For The Sea: Be the change you want to sea.
Innovating to make the world a better, more sustainable place to live. Listen to the race to 9 billion
The Grantham Foundation for the Protection of the Environment: Committed to protecting and improving the health of the global environment.
Energy Foundation: Serving the public interest by helping to build a strong, clean energy economy.
Contribute to Living on Earth and receive, as our gift to you, an archival print of one of Mark Seth Lender's extraordinary wildlife photographs. Follow the link to see Mark's current collection of photographs.
Buy a signed copy of Mark Seth Lender's book Smeagull the Seagull & support Living on Earth