"Invasive species", or "survival of the fittest"?

I want to preface my comments by noting that I will put my credentials as an environmentalist up against anyone’s (well, most anyone’s–I’m not out manning the Rainbow Warrior or anything). My family is car-free, even though we have small kids. We walk or bike almost everywhere, occasionally taking public transit. We are frugal with our energy usage at home, and we even reuse our “grey water” to flush the toilet.

But when I see story after story like this one about the neverending struggle by scientists and bureaucrats to fight “invasive species”, I can’t help but roll my eyes. I guess where I’m coming from is this: if you are a species that has spent eons evolving in a geographic and ecological niche, and another species comes along that evolved someplace completely different, and despite your “having the drop” on the other species you can’t compete, well…then you kind of suck! You are a pathetic weakling, and that other species deserves to eat your lunch.

It also seems like these efforts to preserve native species get more and more labyrinthine to the point where they can not be said to be preserving “nature” in the way we ordinarily understand it.* Furthermore, they seem in the long run to be doomed to expensive and tortuous failure, like bailing out the Titanic with a colander.

How am I wrong? I guess I must be, somehow, because I never *ever *see anyone take this position–not even evolutionary scientists, who you’d think might be interested in seeing species fight it out and show us evolutionary struggle in real time.

*I do recognise the viewpoint that humans are just part of nature, so anything we do is “natural”, and I acknowledge that this has a lot of validity; but it is not the way the word is ordinarily used, and in fact makes the word “natural” meaningless, since in this sense nothing can be artificial.

An ecosystem is a delicately balanced thing, prey learn and adapt so that just enough of them survive, and predators adapt to catch enough for just the right amount of them to survive. Native species don’t “have the drop” on invasive ones, quite the opposite in fact. The native species have only learned and adapted to the activities and abilities of other natives, and adaption is a slow process. So the invasive species often have an edge, prey or predators that often don’t know how to avoid/catch them. This allows them to spread quickly and throw a wrench in the finely tuned engine that is that ecosystem.

The invasive lionfish in the Atlantic a perfect example. A small handful of animals made it into the ocean somewhere in Florida in the 80’s or 90’s, and now they range from North Carolina to the Caribbean. The fish are predatory and eat massive numbers of fish, while few predators eat them. To make matters worse the fish breed quickly and have a large survival rate, so they spread like wildfire.

I think the fight against invasive species is doomed to failure. Mankind will have more and more instances of them, and will have to substitute manual control over nature’s automatic control. Nature always wins out in the end.

The phrase “survival of the fittest” refers to how things are, not how things ought to be. Just because the fittest survive does not mean that is the best outcome. Biologists don’t advocate species invading to see survival of the fittest any more than physicists advocate earthquakes knocking buildings over to see gravitation.

I suppose it’s not really “preserving nature” , but it usually is “restoring nature” - most, if not all, invasive species have gotten to a new area with the help of people. Fish farmers brought Asian carp to the US which then escaped into the Mississippi , people brought kudzu from Japan to the US, etc

It’s all about us. If the invasive species helps us, net/net, then it’s OK. If it doesn’t, then it’s not. And “help” is a broad term here. It might help us physically, medically, esthetically or by some other means. That’s the only gauge, really. Does it help or hurt us?

It comes down to a philosophical stance - is more biodiversity and as many diverse ecosystems as possible a good thing, or not? Science and logic says yes, I think. Devotees of Paveworld might disagree.
It might be OK if it was always a case of “Invader A replaced species X’s niche in ecosystem Ω” and that was it, but it’s never that simple. It’s always “Invader X completely fucked ecosystem Ω over, replacing X, Y and Z’s niches and completely killing off U,V and W. Oh, and it uses 5 times more water than X, Y and Z combined. And it’s an active pyrophyte where all the other species are passive. And did we mention it’s poisonous to livestock and humans?”

Yeah, thanks, Australia.

Not that we haven’t retaliated.

I agree, but only if you take a big-picture view. Often invasives are invasives because they’re useful to humans, much more so than native species. It’s only once we took a more holistic view that we actually saw this as a problem. We could selfishly continue to derive the benefit - I mean, a denuded biosphere only impacts on us in the very long-term, really, doesn’t it?

Bees - who needs them…


That is terrible!

Thankfully African species never behave like that!


As for the OP, I have no idea what the point is. Whether the effects of an invasive species should be mitigated is a moral and economic question, not a scientific one.

If the members of society have decided that they don’t want this shit happening, that’s their decision. It has nothing to do with biology.

I think you missed my last sentence :wink:

Mr. Dibble, I call strawman there. I’m hardly a devotee of “PaveWorld”. As I said, I consider myself a staunch environmentalist. I thought it went without saying, but I’ll say it explicitly for the record: I’m for the highest possible ratio of green space to pavement and sprawl. I’m just not so invested in enforcing exactly what goes on in that wild green space.

But Rubixcube, the lack of knowledge goes both ways. And if it’s so advantageous to be an invader, why don’t all the animals (at least the small ones that can hitchhike) just go invade elsewhere, and we get a complete shuffling of species’ locations but a preservation of diversity? No, I think the successful invaders are just superiour, hardier, more resourceful than the ones they displace. Or are there many documented cases of animals that have successfully “invaded” but which have gone extinct in their land of origin?

And this is bad because…?

I am not saying it is not bad, just that you have not told us, and thus really have not addressed SlackerInc’s question. Furthermore, it is absolutely the norm that this question is not addressed in most public discussion of this issue. We just seem to be expected to acknowledge that all ecological change is ipso facto bad.

If lionfish numbers are growing, then it’s a the expense of something elsey. If the lionfish drives species extinct thanks to human intervention than the world is a poorer, duller place. Further how do you know the lionfish isn’t destroying a species we could learn something useful from? Before, we had lionfish, and whatever the transplanted lionfish are replacing, now we’ll just have lionfish.
SlackerInc, which do you prefer, and island of rats or an island of unique seabirds?
The world’s densest population of rats has been eradicated from an island halfway between New Zealand and Antarctica.

Without human intervention, the rats appear to the be fittest. Except of course getting to the island with human intervention.

To what end do you support “the highest possible ratio of green space to pavement and sprawl”? Only by knowing that can anyone explain to you why invasive species should be controlled.

I’ll say it again: this is not an issue of biology. it is an issue of morality and economics. Only when you can explain what your moral or economic reasons for wanting green space can we explain to you how invasive species are undermining those benefits.

OK, this is gonna be hard. No insult intended, but we really are going to be starting right at the very beginning here. What you have suggested just doens;t make any sense.

Organisms are not islands. Organisms are part of ecosystems. An ecosystem isn’t geography, it is a complex interaction of climate, geography, history the species contained within that four dimensional space. Because of that level of inter-relatedness, what you suggest can’t possibly happen.

Even if organisms were equally able to migrate in all directions (which obviously isn’t true for many, many reasons) the result would be, by definition, to destroy all existing ecosystems. That, in turn, means that organisms that currently live in a loctaion will no longer be adpated to the ecosystems that they find themselves in. As a result most organisms will no longer be competitive and will beocme extinct.

With the multi-directional migrations of the type you describe, what you would end up producing is a weedy environment. You will not be selecting for diversity in any sense of the word. What you will be selecting for are species that are able to rapidly occupy disturbed environments. These species are not in any sense better adapted to niches that they find themselves in, they are just weeds.

To try to understand this, imagine that you took a bulldozer and scraped the top three inches of soil from the entire Amazon Basin. That would kill all the trees, all the large animals and so forth. The entire areas would rapidly be colonised by herbaceous plants that had wind or animal dispersed seeds and the animals that feed on them. That does not allow us to conclude that blackberries and starlings are the “fittest” organisms for the Amazon basin. They clearly area not. All that it allows us to conclude is that they are the “fittest” organisms for highly disturbed and unnatural environment. The plants won’t even survive there in the long term, they will rapidly be replaced with tree species that are able to disperse into the area.

You will have utterly decimated the diversity of the area, having exterminated >90% of all the species that lived there, but you won’t have selected for the species that are “fittest” to survive there. Those are the species that you exterminated. All that you have done is selected for weeds that can thrive in a disturbed environment.

And that is exactly what would happen with the process that you have suggested. You are not selecting for “fit” organisms, unless your definition of fitness is "able to survive in a highly disturbed ecosystem that is utterly and totally atypical of that geographical area.

That’s the very basic explanation, the reality is of course much more complex, but I want you to first accept two points: firstly that “weedy” does not equal “competitive” and secondly that disturbed ecosystems do not promote or even permit diversity. If you can understand those then you will have the bais for seeing the the major flaw in what you posted.

Seriously? :dubious:

So the fact that an invasive species have no local diseases and no local predators that have evolved to eat them makes them superiour, hardier, more resourceful?

That just doesn’t make any sense at all.

Aside from anything else, how do you explain the fact that, in the US, Eucalypts are displacing mesquite, yet in Australia mesquite is displacing Eucalypts? According to what you just posted we have to conclude that each species is superiour, hardier, more resourceful than the other, which is of course logically impossible.

And how do you explain the fact that Prickly Pear in Australia was displacing the native vegetation, until the introduction of a single predator, at which stage it was rapidly displace din turn by the native vegetation? How can the species be “superiour, hardier, more resourceful” in the environment, yet overnight become inferiour, more fragile, less resourceful? Doesn’t this example prove that the success had nothing to do with hardiness or resourcefulness and was entirely attributable tp lack of predation?

Yeah, many. To provide just one example, wild camels are extinct outside of Australia. Hell, camels and horses are both extinct in the US despite having originated there.

But quite frankly I am not quite sure what such examples are meant to tell us. Species extinction rates are very low regardless. If you select any random group of organisms it is unlikely that any of them will become extinct. When you factor in that invasive species are, almost be definition, weedy species they are the very ones that would be unlikely to become extinct in the short term regardless. That doesn’t make them superior to the species int he environments in which they become established, It doesn’t even make them superior as weedy species. All it tells us is that weedy species are less prone to extinction and invasive species tend to be weedy.

They are predators, that doesn’t make them “fitter”. They aren’t competing with the birds, they are eating them.

This is a common misunderstanding of natural selection. People think that predators are “fitter” then their prey, when in fact the species aren’t competing in any way at all.

The real animals that the rats are “fitter” than are whatever was originally preying n those seabirds. Except that there wasn’t anything. So the rats weren’t successful because they were "fitter’ than something else. They were were just invasive.

I think proponents of PaveWorld are the ones who would call a species invasive. It is upsetting whatever precarious and possibly illusory balance existed which we happened to like. There’s no question that any species which can latch on to humans is, right now, poised perfectly to dominate (in the sense of reproducing faster than competitors). If that species is a pest species, all the better, because we won’t be eating them. From bacterial diseases to inedible fish, pest species which can benefit from humans will do so, at the expense of those species we happen to like as those qualities which make the species likeable to us are exactly the qualities that hinder their dominance in an otherwise hostile environment. Docile bees whose honey we take? Meet aggressive bees who get to keep their own honey. Fish we cull? Meet fish we don’t. Diseases we treat? Meet diseases we don’t. In our struggle to control our environment, we’ve attempted to select just those species amendable to control. But those qualities mean we have an obligation to act in their stead for their defense. If we don’t like foxes in the henhouse, we’ve got to kill the foxes; maybe some killer chicken would have evolved to defend against foxes (or maybe not) but we’d be sure that never happens anyway, so we’ve got to assume the burden for the chickens. Obviously we could never eat the chickens fast enough to starve the foxes without losing out on eating chicken in the future.

It’s probably always going to be a losing battle for us, because we’ll always desire to have more resources available than we’re using at any one time, meaning there is always going to be a niche for pest species of some size, nematode to insect, fish to mammal. And probably all sizes. It’d be the dream of dreams that we live on a world made only of food and beauty—a dream for every species. I doubt we could create it for just ourselves.

Not only isn’t any of that that true, it is actually self-contradictory.

We can’t be “selecting just those species amendable to control” if “species which can benefit from humans will do so, at the expense of those species we happen to like as those qualities which make the species likable to us”. One or both of those statements must be wrong. In this case, both are wrong.

The rest of it s equally erroneous.

Oh, Blake…don’t ever change, you crazy beautiful cat, you. ;0) (Psst: you are arguing on both sides of the issue here, bud. Just FYI.)


I can buy that: it’s a really good point. But if we’re going to go that route, it seems more reasonable to do it on a smaller scale in parks or really game preserves that don’t make any pretense of being “nature”. It’s when biologists, working with bureaucrats, attempt to prevent species from being introduced anywhere in an entire region that it starts to have the whiff of madness from my perspective.

Uh huh. So we take the time to explain the issue to you, and you simply dismiss it.

Since you clearly neither wish to debate this nor to understand the issue I am finished with you. i have students who are actually interested in real ecology to attend to.

It really does keep fighting back.

No…please…Blake, I beg of you…give me another chance!

(Or, don’t. I’m good with that, actually.)