Let the Invasive Honeysuckle Take Its Course, Says Report

Transcript

OPEN: It's estimated that over 100 billion dollars is spent in the United States each year trying to eradicate invasive species. But a Penn State study says there's evidence that invasive honeysuckle can be beneficial to some ecosystemsóin this case by fostering the growth of bird populations. Anthony Brino reports for WPSU.

NAT SOUND: walking

CARLO: Well, you can see over here, for example, there are mostly Mackii honeysuckle. Essentially they have been spreading in highly disturbed habitats, like this one.

BRINO: That's Tomas Carlo, an ecologist at Penn State University, walking through Sunset Park in State College, part of a larger area surveyed by his lab team. In the fall 0f 2009, they found birds like Robins, Starlings and Cedar Waxlings embracing an abundant food source, the berries of invasive honeysuckle.

CARLO: One of the reasons this honeysuckle system is working so well is because one of the species fruits earlier, in June. It has a very sharp peak ó it peaks in July, August ó then drops quickly. And that's about the timeóin late August and Septemberówhen Morrow's honeysuckle starts ripening. So what you have is a big time when these fruits are available.

BRINO: In an article published in the academic journal Diversity and Distributions, Carlo's team argues that since honeysuckle supports bird communities in central Pennsylvania, it shouldn't be considered an ecological detriment.

CARLO: Patches of honeysuckle are favored by birds that are generalists. And they also disperse everything that's around them...These birds are essentially the dispersers of everythingónative, alien, introduced, whateveróand these are also migratory birds, so they go to the tropics and other regions to do the same thing.

BRINO: In the 1950s, Honeysuckle was used to minimize agricultural run-off and foster wildlife. It's since taken over large swaths of the east coast, and is a major frustration for conservation biologists, botanists and landscapers, who would typically try to remove it from an area, then plant native shrubs. Carlo and others see that as a waste of time, since nature is already doing its own thing.

CARLO: We have modified the habitats, essentially destroyed original ecosystems, and then we have brought new elements. And when we give a chance to nature, nature starts coming back. And these novel communities have elements of both native and introduced species.

BRINO: Still, honeysuckle is reviled for a reason; it can lead to a lack of diversity. It hinders forest growth and its berries are not very nutritious, offering little more than carbohydrates. Honeysuckle doesn't support insects, which means it doesn't support insect-eating birds. And like the melodious Wood Thrush, many bird species have co-evolved with native plants that are starting to dwindle, says Margaret Brittingham, an avian ecologist at Penn State.

BRITTINGHAM: Spice bush is used heavily by migrants, particularly species like the wood thrush, a close relative of the robin. It's also a fruit eater during the fall, it's a species that's declining.

BRINO: Brittingham says that Carlo's research does highlight a complex dilemma.

BRITTINGHAM: If you're going to get rid of them, you need to do something else. You need to put something else in there. So if on a local area you say, I'm going to try to get rid of all this honeysuckleówhich is difficult to do and as they said it's expensive and it may be futile. So what that means is that when we think about removing invasive, we need to think at the same time about the native species that you're going to get back in there.

BRINO: As part of their study, Carlo's team took fruiting American Nightshades, a native shrub, to fields dominated by honeysuckle. The birds ate the berries of both plants, and presumably spread the seeds of both. This, Carlo says, could be a relatively hands-off way to help re-establish native plants and ultimately promote biodiversity.

CARLO: One of the cheapest ways to achieve ecosystem recovery is to use the natural processes that are taking place. So instead of trying to fight it, we can dance with it. We'll maybe be more successful.

BRINO: But others disagree.

TALLAMY: I really don't like trashing other people's research because I know how hard it is to do and it's always out of context so I'll just say that up front.

BRINO: Douglas Tallamy, is an entomologist at the University of Delaware and the author of Bringing Nature Home: How You Can Sustain Wildlife with Native Plants.

TALLAMY: So I liken this to say we are out of space and we come down to earth and we decide we are going to study what is good for humans to eat and we only study ice cream parlors. We can demonstrate that humans go there and they eat ice cream. But to conclude that that's good for humans and that's the only thing they need is very misleading. And that's kind of what I'm getting from this study.

BRINO: Carlo acknowledges that in most cases, invasive species are detrimental. But in the case of honeysuckle, he thinks evolution could resolve the issue without humans spending their time and money. For WPSU, I'm Anthony Brino.