January 31, 2011
Are Humans an Invasive Species?
Are humans an invasive species? (photo courtesy of flickr user Mike PD)
Some readers of recent Smithsonian stories on wild pigs in Texas and the world’s worst invasive mammals list have argued that we may have left out the worst invasive species of them all: Homo sapiens. But are humans really an invasive species?
Let’s start with the definition of an invasive species. It turns out, it’s not so simple. The legal definition in the United States is “an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health.” The International Union for Conservation of Nature (IUCN), which developed the list of the 100 world’s worst from which our invasive mammals piece originated, defines them as “animals, plants or other organisms introduced by man into places out of their natural range of distribution, where they become established and disperse, generating a negative impact on the local ecosystem and species.” And a 2004 paper in Diversity and Distributions that examines the terminology of invasiveness notes that their is a lack of consensus on this topic and lists five dominant definitions for ‘invasive,’ the most popular of which is “widespread [nonindigenous species] that have adverse effects on the invaded habitat.”
Despite the lack of a single definition, however, we can pull from these definitions some general aspects of an invasive species and apply those to Homo sapiens.
1) An invasive species is widespread: Humans, which can be found on every continent, floating on every ocean and even circling the skies above certainly meet this aspect of invasiveness.
2) An invasive species has to be a non-native: Humans had colonized every continent but Antarctica by about 15,000 years ago. Sure, we’ve done some rearranging of populations since then and had an explosion in population size, but we’re a native species.
3) An invasive species is introduced to a new habitat: Humans move themselves; there is no outside entity facilitating their spread.
4) An invasive species had adverse effects on its new habitat and/or on human health: Humans meet this part of the definition in too many ways to count.
Verdict: We’re not an invasive species, though we’re certainly doing harm to the world around us. If you think about it, all of the harm done by invasive species is by definition our collective faults; some kind of human action led to that species being in a new place where it then causes some harm. And so I’m not at all astonished to find people arguing that we’re the worst invasive species of them all.
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I do agree with your verdict, although I would have gone into the semantics of it all; humans cannot be an invasive species as it is a man-made notion. And, seeing how we cannot be invasive as we move about ourselves, I wonder if perhaps our “invasiveness” isn’t more a symptom of a species exploring its own potential in terms of population growth; we’re simply too well adapted to the world. So, in a way, we’re not invasive, we’re just highly successful. Although I should hasten to add that population growth cannot resume forever; at one point or another the trend will reverse, and the population stabilise. It is very interesting to ponder what that level is, but as it has little to do with the topic, from which I have already digressed, I shall refrain.
[...] This post was mentioned on Twitter by SmithsonianMag, Sarah Zielinski and SmithsonianRSS, vera van dalen. vera van dalen said: RT @SarahZielinski: Some readers have claimed that humans are an invasive species. Technically, they're wrong. http://bit.ly/eOTVjy [...]
Some people, even experts, may not define people (humans)as invasive, but we are invasive, environmentally destructive, and perhaps the greatest perpetrators of the destruction of species diversity on this small planet. There are more people than locust, the architypal plague beast.
[...] starting to think of us as the worst invasive species; taking over and wrecking any environment we find ourselves in. These are not the kind of thoughts [...]
While humans may not meet every component needed to qualify as an invasive species, we are clearly the most destructive. However, disqualifying the human race as an invasive species says more about our tendency of creating rigid categories than to whether we belong on the list of “invasive species.”
OK then, we’re not an invasive specie but something far worse!
On #2.
The author notes we had colonized every continent by 15,000 years ago, which is about what contemporary estimates indicate. Anatomically modern humans originated (according to Wikipedia) around 200,000 years ago, in Africa of course. Our adaptability made it easy for us to quickly (in evolutionary timescales) colonize the entire planet. However, shouldn’t we still be considered non-native to regions outside Africa? It is possible (even inevitable) that within another 5,000 years we will have colonized Mars. Would that make us native to Mars? I should think not. We would be invaders, just as we were invaders to the Western Hemisphere, and to a lesser extent, Asia and Europe.
Seems like this argument is a little slippery and and does not focus attention on the nasty business humans do.
According to Wikipedia, a secondary definition of the term invasive species “…broadens the boundaries to include indigenous or native species, with the non-native ones, that disrupt by a dominant colonization of a particular habitat…”
There should be no argument about the devastating influence of humans as the most destructive, non-natural force on earth.
If you follow the anthropological evidence which strongly suggests we’re not native from this planet, you’ll find experts on the subject who argue that we were possibly brought here and genetically engineered with the DNA of native species’. This would offer the plausible argument that we are infact an invasive species by satisfying both the second and third conditions per the collaborative definition. I would contend that nothing within the definition of invade, or invasive suggests that outside influence is required. Therefore condition three is inherently satisfied. Condition two is also satisfied if you follow anthropological evidence showing that we as a species originally developed in Africa, from where we spread, which satisfies condition two. In summary, whether or not you believe, or follow the theories of our non-native nature to this planet, we would still be considered an invasive species. However, the rapid evolution, as suggested, does indeed fly in the face of every Darwinian Evolutionist and Anthropologist challenging the many theories they support still today. The convenient “missing link” theory they fall back on is fundamentally flawed. Decades upon decades of searching has delivered much evidence and evolutionary record of the native bipedal species on this planet. However, our skeletal structure is too far removed from any considerable similarities. The amount of evolutionary evidence required to explain the numerous differences between us and them is far to great to be satisfied by a single “missing link”. The fact that not a single shred of evidence having been discovered, in spite of all our searching, to support the “missing link” theory is compelling enough to raise the question, “are we truly native to this planet”. According to the widely accepted theories on evolution, we’d have to accept that this question is at least valid. Yet it is not officially pursued. Why not?
HUMANS ARE INVASIVE!!! Africa is the cradle of mankind the earliest fossils point to this place. Africa also happens to be home to some seriously dangerous animals and diseases. Lions,leopards,Cheetahs,Hyenas,Nile Crocodile,Great White shark, spitting cobras, Hippos,Puff Adder, Chimpanzees, Elephants,Black Mamba,Cape Buffalo, Malaria,Dengue,Yellow fever,AIDS,Hepatitis B,Cholera,Typhoid…all documented to have killed large amounts of people. Why do all of these dangerous animals,diseases exist in Africa? TO KEEP HUMAN POPULATIONS IN CHECK. No where else in the world are there that many dangerous creatures except for Africa where humans are native to.