Climate Change and Establishment Means

Disclaimer: I’ll be using the United States for my thought process here, but this could apply to other places as well.

As a result of a warmer climate, many species, even native ones, are beginning to expand their range northward to places they had never inhabited previously. For example, the Southern Yellowjacket (Vespula squamosa) is native to the Southeastern United States, but has recently been expanding north into New York, Connecticut and Rhode Island, and may possibly reach the rest of New England in the coming decades.

My question is this: Would species like V. squamosa be considered “introduced” to these new regions, or “native”? I can see both sides to this. While these species are expanding their range naturally, they probably wouldn’t have been able to do so without human anthropogenic means (fossil fuels). Maybe its something else entirely. What do you think?


I would say that these climate change assisted migrants would not be considered introduced to these regions for several reasons.

For ones, while humans created (and are creating) the conditions that allow the species to survive in areas where they haven’t been able to survive before, the organisms are migrating on their own (ie, colonizing without direct human intervention). If they are human assisted in the specific act of moving (intentionally or unintentionally), then I would consider them introduced. But that is really the crux of “introduced” to me.

On a broader scale, climate has been changing “on its own” for millions of years (albeit generally at a slower pace), and organisms’ ranges have been changing as well. So what you describe is not a new process, just a change in the rate of a pre-existing one.

From a classification perspective, I also think that it is valuable to know whether a species arrived via anthropogenic means or not. This is iNat’s definition of introduced - it’s about methods of arrival, not whether humans created conditions allowing for establishment of a sustaining population or not. As someone who has worked in invasion biology, the processes that lead to invasions that require human-assisted dispersal are treated differently in some (though not all) ways than those where a species can move to a new range itself. For one, there are likely no ultimately effective ways to prevent spread in most cases when an organism can move on its own!

So, in general, while I think climate change certainly plays a role in allowing establishment of new populations and expanding ranges, it is still a distinct process from human-mediated introductions, though it does interact with those.


How long do the records go back? Do they cover the 10th century, when the Norse were farming on Greenland or the Roman Warm Period?



I think contiguous expansions of the native range are native, even if humans influenced the climactic conditions behind the range expansion, since this is a species naturally living where the habitat is suitable. So the Southern Yellowjacket would be native in CT

Introduced would be if humans transported the species somewhere it would not otherwise be, like the Red Imported Fire Ant that was brought to the US on ships form South America. If the fire ant’s range in the US expands northward due to climate change, that is still introduced, since it wouldn’t be here at all if not transported by humans


I agree that a species expanding its range due to climate change should not be considered introduced. “Introduced” is really for situations where humans directly introduce a species to a new place (whether it’s intentional or not), not whether human actions indirectly create conditions for a species to spread from its native range.


Might be displaying my ignorance here, but I am not sure if ‘native’ or ‘introduced’ is a field that can be selected for an observation on iNaturalist. Certainly ‘wild’ or ‘captive/cultivated’ is a field. Feral organisms can still rate as wild. In any case I think that there are many ways that we humans having affected the distribution of species apart from climate change. These include ecosystem modification, e.g. clearing a forest to create a pasture, the removal of predators or competitors and the widespread introduction of new species to different regions either deliberately or accidentally. In answer to your question, I would say ‘native’.


Introduced isn’t something that is determined at the observation level on iNat (though it does display on observations). It is determined by how the species is designated for specific places, so all observations of a species in a given place will have the same introduced/native/endemic status. You can read a bit more about this here:
and other places.



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In British circles things that are natural arrivals are usually considered native.

For example, Macroglossum stellatarum (a hawk-moth) was until very recently only known as a natural migrant - it’d fly here from the continent on it’s own steam, breed, but never survive the winter. Now it’s starting to colonise and thrive in the South. It’s considered a native even though it wasn’t established here a few decades ago.

That actually applies to stuff that hasn’t and can’t colonise here. Monarch butterflies sometimes turn up here - the migratory ones get blown off course sometimes - and those are listed as native too despite the fact there’s no milkweeds here and they couldn’t possibly establish. They (mostly) get here without human help, they’re so ‘native’.


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