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Non-native species: Bad or Good?

November 3, 2011

A theme of The Highest Frontier is “invasion” by non-native species, like kudzu, cane toads, and space aliens.

But are non-native species always harmful? In the northeastern USA, the dominant earthworms arose from non-native species in the nineteenth century; they have enriched the soil. Other non-natives with positive benefits include honeybees, plants that feed butterflies, and non-native fruit trees that feed birds. And there can be plus-minus effects. Even the infamous zebra mussel has  clarified water and increased fish populations of some lakes.

Are non-natives in fact any more invasive than native species? Climate change can cause native species to become invasive; for example, increasing temperature in Alaska and Canada allows the native spruce beetle to kill off forests.

If species introduction can have positive and negative effects–both hard to predict–then who should decide? Should any person have the right to dump their snakes or aquarium plants into the environment and see what happens? Or should we “regulate” this?

  1. Trey permalink
    November 4, 2011 9:23 am

    Tough one. I go with a ‘do the least harm’ which means that the governments should regulate it – with the intent to slow the spread (its going to happen no matter what) and study it to see the impact. Then, if necessary kill the hell out of the introduced species. Examples include grass carp, snake heads and walking catfish. And if it doesn’t should include pythons.

    This is something I’ve thought about since I was a kid and National Geographic had an article on introduced species in Florida. Then again after reading 1491 and visiting Tenochitlan and seeing grass around the pyramids. I think my in-laws thought I was blown away – I was but not in the way they expected. I was by the extent of ecological change. Even at home in Mississippi, I look around and see some of the changes introduced species have made.

  2. November 4, 2011 12:08 pm

    Since we’re the number one invasive species across most of the globe, we do need to look in the mirror on this one. Moreover, the desire for exotic species like sugar and tobacco have certainly created a lot of misery over the last 500 years.

    I’d rather be for native species, wherever they’re native. Sometimes that means being against non-natives, mostly that means valuing where one lives, and thinking before giving in to the seduction of the exotic.

  3. alex tolley permalink
    November 4, 2011 10:26 pm

    And not just non-native species – we introduce new genes, gene engineered organisms, etc, etc.

    My sense is that conserving native populations may be about as futile as preserving privacy, at best one is fighting a rearguard action to delay eventual invasives.

    I suspect we will be saddened by the loss of native ecosystems, much like the loss of native languages. However, we will be continually terraforming the planet to make it more comfortable to us. There is a benefit to that too.

    • November 5, 2011 1:22 pm

      Saving natives isn’t romantic at all. It’s eminently practical. I work mostly with plants, and I’ve been having a lot of fun with the new evidence that some native plants are more fireproof, use less water, and cost the same as the exotics that people try to replace them with to be more fire-safe. They also support the bees and things that pollinate our vegetable gardens. That’s the cost of prejudice and ignorance right there.

      Actually, there are two great arguments for saving natives. One is that people have lived off them for millennia, while agriculture based on importing plants, water, and fertilizer is running into serious trouble after a century. If industrial ag fails, at least a few people can survive on the remnants of the natural system. It’s a lifeboat.

      The other argument is that we can either support systems that we can wipe out if we’re not careful, or we can wipe them out, thereby paving the way for organisms that take advantage of us, and that we *can’t* wipe out. These are known as pests, pathogens, and parasites. Seems to me that being the kingpin keeping the system together is a lot safer than being the most abundant underutilized resource.

      To put it simply, would you rather camp in a field of wildflowers, or a field of thistles?

      • alex tolley permalink
        November 5, 2011 3:35 pm

        I think we need to be a bit careful with statements about the desirable properties of natives. There will always be some natives that have more desirable property X than some exotics. That doesn’t mean that more careful choice of exotics couldn’t compensate.

        US ag is based heavily on a native species – corn (if you can still call the plant native). This is in stark contrast to non-native wheat, which is still dominant in Europe. Maybe the foreign exotic is “better”.
        It is more likely the monoculture and crop selection and farming methods that is going to be at fault, not whether the crop plant is native or exotic.

        While there is always likely to be some ecosystem level adaptation over time that results in a more fit local ecosystem, I don’t believe that we can definitely say that artificial ecosystems or modified native ones cannot be made more fit or better suited to some desired goal.

        • February 1, 2012 2:31 am

          Hi Lee, the Chytrid fuungs can be introduced into a site in many ways. If infected frogs move from one stream to another during natural movements, then the fuungs will spread. People can also transport the fuungs on infected equipment and shoes, and introduced amphibians can also transport the fuungs. Once the fuungs is found in an area, there is no way to eradicate it, as it remains in the water and moisture of the soil. It is a water-borne fuungs.While most frogs metamorphose in a few months, the mountain yellow-legged frog takes at least two seasons to morph; this is because of the cold temperatures and short summer “growing” season. My next blog will be up sometime next week.

  4. November 4, 2011 11:00 pm

    Perhaps the “rearguard action” is the most valuable, because what really matters is the speed of change. Before humans existed, there was always change; new species were always being introduced into environments. But what humans do is to speed up species transfer. Rapid introduction means that an environment has no time to adapt; no time for pathogens and predators to evolve to deal with the newcomer. So if we slow the pace of species transfer, we still maintain better quality of ecosystems, even though eventual change is inevitable.

  5. Robert Robbins permalink
    November 7, 2011 1:24 pm

    Ultimately all life in all environments is invasive. If there were no invasive species, Hawaii would be bare volcanic rock. If there were no invasive species, there would be no terrestrial ecosystems. Life responds to change (either environmental or biological) through invasive species. After Mount Saint Helens, species had to re-invade the destroyed areas; after the end of the dinosaurs, the massive mammalian radiation involved invasive species. After any perturbation, a new equilibrium is reached through (among other things) species invasions. Humans, with the advent of the anthropocene, have introduced major perturbations into the biosphere. We can expect, as a result, significant species relocations (or invasions). Attempting to prevent species movements after a perturbation is like trying to prevent cell movement after a wound: it is difficult to achieve in the long run and is ultimately counter-productive.

    • November 7, 2011 5:04 pm

      I’ve got to disagree somewhat. I’ll use one example of a rather obnoxious weed people are fighting: Euphorbia terracina. It’s ugly by any standard–it’s small, spindly, the flowers are little green nubs. Worse, the sap is toxic, and some people react to exposure with a full-body rash worse than poison ivy. It’s native to (and rare) in most of the Mediterranean, but apparently one genotype from Spain is quite tough. That genotype has invaded Australia and now the US.

      Why is it in the US? Not because it’s a good colonizer. Rather, someone sold it as a “hardy house plant” some years ago. A few people bought it, thought it was ugly, and left it on the edge of their patio next to a park. It’s now spreading through the park and elsewhere.

      Never underestimate the role of human greed and stupidity in the spread of weeds, and never underestimate the role of education in stopping their spread. One of the best places to see this is in the noxious weed lists from various states. A few listed noxious weeds are widespread, but most aren’t found in the state, because they were caught and eradicated before they got out of control.

      As for counter-productivity, I deal with wildland weeds, but most of the noxious weeds on the list are crop pests. If we don’t do a good job controlling these, agriculture suffers quite a bit.

  6. November 7, 2011 7:16 pm

    Interesting example of how international trade turned two minor infections into that chytrid that’s killing amphibians worldwide:

    • November 7, 2011 8:49 pm

      That’s interesting about the chitrid strain; thanks for the new info. Although it’s still not really clear how the two strains mated. Invasives cause no end of trouble–it seems only common sense to screen for them. If the USA had required fumigation of wooden crates from China back in the 80s, we would have no long-horned tree borers. (And stuff from China would cost more, as it should–another topic.)

      But Robert is right too. There is a new study of “ragamuffin ecosystems;” that is, the half-wild half-mixed ecosystems upon islands and growing up around cities. Some of these ragamuffins are as interesting as “pristine” ecosystems.

      Are “foreigners” always more invasive; or are we just more aware of them when they are?

      **The bottom line question: What constitutes a good or desirable ecosystems? Number of species–how to define? Beauty of species–how to define? Toxic to humans–what about poison mushrooms and frogs?

      • Robert Robbins permalink
        November 7, 2011 9:57 pm

        I should have been more clear in my earlier post. Of course there can be many human reasons – aesthetics, economics, whim – for preferring native over invasive species. My point was that there is no purely scientific reason for doing so, and certainly not in an historic context, where all species are invasive, and all ecosystems have displaced some previous ecosystem. How, from a purely “scientific” perspective could we define a “better” ecosystem (or a “better” species, for that matter)? If we opt for “non-disturbed as a criterion, then we have to prefer the cretaceous over the tertiary, or even the paleozoic over the mesozoic. If we like the results of the mammalian radiation, does that mean that the massive devastation at the end of the cretaceous was a good thing? If we dislike perturbations that lead to major extinctions, then we should oppose the evolution of photosynthesis, since that lead to the entire atmosphere being loaded with oxygen, which was completely toxic to the world of obligate anaerobic micobes that made up much of the earth’s biota before photosynthesis. All major evolutionary advances are disruptive. Photosynthesis killed the anaerobes, the evolution of jaws rendered obsolete many previous designs, and the development of sentience and then culture in a narrow lineage of primates is promising to be one of the most disruptive evolutionary events yet. The essence of life is evolution, and the essence of evolution is change. When one lineage makes a major evolutionary advance, the other lineages must evolve fast or lose and go extinct. Sentient primates have made a big move and the rest of the biosphere will be affected. My personal preferences and aesthetics tend toward the “natural” – that is, towards ecosystems with little or no human impact. But, the scientist in me is forced to concede that I cannot make a scientific case for the superiority of the “natural” ecosytem.

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