A New Look at Invasive Species (2015 version)

15-15 A New Look at Invasive Species

Gary Price: There has been a lot of talk about how certain species of non-native plants and animals are upsetting the eco-systems in various parts of the United States and the world. South Florida is dealing with Burmese pythons; many Midwestern rivers are overrun with Asian carp; and plants such as Japanese knotweed and English ivy are choking out other, more desirable, plants in gardens, woodlands, and developed areas in the U-S and overseas. How did these alien plants and animals get here? Are they really that harmful? And what can we do, if anything, to contain or eradicate them? Fred Pearce is a British science journalist who has studied the issue extensively. He writes about it in his new book, The New Wild: Why invasive species will be Nature’s salvation. We asked him what an invasive or alien species actually is.

Fred Pearce: Well, we’re talking about alien species that have come in from outside and take hold. People then talk about them being invasive. Actually, you could have domestic species that are invasive too, but we kind of tend to ignore them. We get a downer or foreigners, basically. We’re talking about foreign species coming in where they haven’t been seen before. People get a bit upset about that.

Price: In the U-K, it’s the Japanese knotweed that’s got people up in arms. There is even an official “Japanese knotweed officer” – the only one in the world — headquartered in Swansea, Wales to keep track of and try to eradicate the plant. But where did it and other alien species come from?

Pearce: Sometimes it’s deliberate. Japanese knotweed here in the U.K. — it was brought in by gardeners, Victorian gardeners, about 150 years ago. They look pretty good in the garden, but then they escaped over the wall and started spreading around through the suburbs. Sometimes nature brings them. They just fly in or they can move around, especially marine species move around on the ocean currents. That’s pretty normal, it’s been going on forever. And sometimes they hitchhike a ride. They turn up in grain stores or they just travel with the grain, or they may travel in your backpack, or they come in cargo holds. Ballast water tanks on ships are a big way of moving marine species around. So if you go to San Francisco Bay, hundreds of alien species there, and most of them arrive on ships one way or another.

Price: The numbers of many invasive species are amazing…at least on their face. Pearce says that the way many governments count the infestations of aliens is exaggerated and makes it sound like an entire region is overgrown when, in fact, there might not be more than one or two of the plants in the area…

Pearce: I came across a case of a weed in the U.K. which goes along riverbanks and, you know, you see it from time to time, but the surveyors said that if you find one example on a stretch of riverbank they will mark it down that that riverbank has been “invaded.” So, then you add up all of these bits of the riverbank that have been “invaded” by this plant, and it looks like it’s taken over the whole riverbank for miles and miles and miles and it’s complete nonsense. There’s just a few examples.

Price: Pearce says that often “invasions” by these foreign plants are blown out of proportion. He suggests that we all calm down, and quit being so paranoid about it. Tao Orion agrees. She’s a permaculture educator and author of the book, Beyond the War on Invasive Species: A permaculture approach to ecosystem restoration. She says that often a so-called alien species, like the Japanese knotweed, isn’t so much an “invader” as it is a way for nature to reclaim the land that humans have made uninhabitable by native species…

Tao Orion: One of the concerns with Japanese knotweed is that it appears to crowd out native vegetation. But one of the issues that I see is that given this degraded state of streams and waterways and the temperate climate overall, basically, of America, England, Europe, is Japanese knotweed the only type of species that will live there now? Because we don’t even know if native species will survive and thrive in the type of environments that we’ve created. So is the issue the knotweed or is the issue the way that we use and interact with waterways and water resources?

Price: As for alien plants overtaking native species, Orion says that many of those flowers, trees, and other plants that we call native aren’t the result of Mother Nature’s haphazard spreading of seeds around the country. In fact, they were put there by design and cultivated by humans…

Orion: A lot of plants species and animal species that we think of as native or as wildflowers were actually managed by indigenous people in the Americas for food and fiber, for medicine. And that’s an aspect of this whole kind of invasion ideology, but I think is really missing up to this point. And it’s something that I researched a lot for this book, and what I feel now is that if we want to preserve and enhance populations of native species, then we have to engage in similar types of management of their populations, similar to what indigenous people practiced, which has been, pretty much, not part of the discussion in or out of restoration contexts.

Price: By the same token, many animals that are considered native are not native at all. Pearce says that Europeans who came here from the Old World brought two of our most beneficial bugs with them…

Pearce: You didn’t have earthworms until they showed up from Europe. You probably did before the last Ice Age, but the last Ice Age, it wiped them out of most of North America except down in the far South. Earthworms came back when Europeans showed up. Completely changed your soils. Honeybees. Everybody gets very worried about the diseases that have been attacking honeybees, and we’ve got to save our American bees. Guys, you didn’t have any bees until Europeans brought them over 500 years ago. So, surprising things that you think are kind of a natural, native part of the environment, turns out they showed up from somewhere else a few hundred years ago.

Price: He says that when alien species show up like the earthworms and the honeybees did 500 years ago, nature usually has a way of making them fit into the ecosystem, so we shouldn’t panic but allow the earth time to work it out for itself…

Pearce: We tend to think that species of kind of plants and animals and insects and so on have “co-evolved” is a phrase that gets used a lot over millions of years to be, sort of, perfectly fitting into their local ecosystem. But if you talk to ecologists who actually analyzed how ecosystems really work, they find it’s very different. The find species are constantly moving in and out; animals are eating one thing and then move on to eat something else; they get eaten by one thing and then get eaten by something else. Everything is kind of much more dynamic and it’s a sort of a constantly changing kaleidoscope with species. There are not many places in the world where ecosystems are unchanging. And probably where they are unchanging, it’s really rather unhealthy because they’re more vulnerable.

Price: One of the horror stories is the Burmese python in South Florida. There’s a bounty on these invaders, but no consistent and effective method has yet been found to eradicate them. The pythons prey on small to medium-size animals such as rabbits, raccoons, bobcats, and some birds, but rarely attack humans. Orion says that, again, we need to look at the areas they inhabit, find out why they are comfortable there, and determine what role they play in the larger eco-picture. She says that, eventually, they could fit into a niche in the Everglades and live there as easily as the alligator…

Orion: One of the things about invasive species that appear to be proliferating and out of control – quote, unquote – is that over time, everything kind of comes into balance with its surroundings. That’s how evolution works. Like it doesn’t really make sense for an organism to just grow exponentially and not have any checks and balances in its ecosystem, it just doesn’t happen. And it may appear to happen over the short term. But over an evolutionary time frame, some things are going to be acting on that organism to control their populations.

Price: All in all, Pearce says that change in nature is good – it’s what keeps our ecosystems robust and our landscapes ever-changing. After a while, we usually get used to these invaders and can embrace them as the movers and shakers of the ecosystem…

Pearce: I think change is good. Change is what is wild about nature. And we should cherish that. Look out for some of these incoming species – the go-getter colonists. These are like go-getter humans. These people come in and can be disruptive, these species can be a bit disruptive, but we need them as part of the dynamism of our ecosystems the same as we need people coming in from outside to be dynamic, to be go-getters in order to keep our societies going. So I think maybe there’s balance, I don’t know. We certainly need them.

Price: You can find out all about the good side of invasive species in Fred Pearce’s book, The New Wild, available in stores and online at Beacon.org. You can find Tao Orion’s book, Beyond the War on Invasive Species, at stores and on the website resiliencepermaculture.com. To learn more about all of our guests, log onto our site at viewpointsradio.org. You can also find archives of past programs there and on iTunes and Stitcher. I’m Gary Price.