07 November 2009

Invasive species not so bad?

Over on Slate, Rebecca Tuhus-Dubrow says some conservation biologists are starting to question the importance of preventing species invasions:
Certainly, they say, non-native plants and critters can be terribly destructive—the tree-killing gypsy moth comes to mind. Yet natives such as the Southern Pine Beetle can cause similar harm. The effects of exotics on biodiversity are mixed. Their entry into a region may reduce indigenous populations, but they're not likely to cause any extinctions (at least on continents and in oceans—lakes and islands are more vulnerable). Since the arrival of Europeans in the New World, hundreds of imports have flourished in their new environments.
Tuhus-Dubrow cites the case of Tamarisk in the U.S. Southwest -- an aggressive introduced shrub that has also ended up providing important nesting sites for the endangered southwestern willow flycatcher.

The fact of the matter is that human-introduced species can eventually integrate into an ecological community; once they do it's hard to get them out, and problematic as to whether it's a good idea. In Australia, dingoes helped extirpate many other large predators when they were introduced by the first humans to arrive on that continent -- and now they're critical to controlling other, later-introduced mammal species.

(Thanks to Ephraim Zimmerman for point this one out to me!)

Invasive pest, or critical flycatcher habitat? Maybe both. Photo by Anita363.


  1. I have a couple problems with the article. While these non-natives may provide nesting habitat and sometimes food (think of honeysuckle and autumn olive in the east) for one or two species, they often host significantly fewer pollinators and herbivores - which could have a significant domino effect. There have been several studies showing substantially fewer insect species on non-natives than similar native species.
    Maybe tamarisk was not the best example. Nothing like having a beautiful house without anything to eat!
    - and what's with the H1N1? Is that an "invasive species?"

  2. That's a good point. There are a lot of species interactions to consider before you decide to stop trying to remove an introduced species. I should've noted that by the time invasives "naturalize," the community may look a lot different from the way it started -- and not in any predictable way. Certainly it's much better to avoid the decision of how to treat an introduced species by avoiding the introduction from the beginning.

    (And, yeah, I don't get H1N1 as an "invasive species," either, except maybe within the context of the human microbial community -- but then that would apply to any disease organism!)