I think it would be good if “reintroduced” and “self-introduced” categories were added to the establishment means for iNat. “Reintroduced” could be symbolized by a blue plus sign while “self-introduced” could be symbolized by an orange plus sign (much like how endemic and introduced are symbolized by a green star and a pink exclamation mark).
“Reintroduced” could be used when an animal is either purposefully or accidentally reintroduced to an area where humans previously wiped out it or a close relative. Examples would be elk and red wolf in the eastern US, wolves in western and central US, certain groups of wild horses and cattle in Europe (i.e. those at Oostvaardersplassen preserve in the Netherlands), black swan in New Zealand, yellow-crowned night heron in Bermuda, scimitar oryx in northern Africa, etc. Of course, there is some gray area in here, such as Aldabra giant tortoises in the Mascarene (the extinct Mascarene tortoises belonged to a completely different genus, so would this count as reintroduction?) and feral horses in the United States (there’s already a huge controversy over whether or not it counts as reintroduction).
Self-introduced refers to documented cases of an animal establishing populations by itself in a new area. Examples would be cattle egret in the Americas, glossy ibis in the United States, Eurasian collared-dove throughout Europe, green iguanas on Anguilla, and silvereye in New Zealand. Of course, there are still some gray cases here too (the monarch butterfly most likely spread throughout the Pacific by itself, but this was mainly due to humans introducing invasive milkweed to many Pacific islands, so would this really be natural?).
I think that including these two categories as establishment means will help to paint a finer portrayal of the complex nature of species establishment.
I’m not sure the 2nd one makes sense to me. All ‘native’ species are self-introduced. That it happens to have taken place at a timeline allowing humans to document it is not a differentiating factor.
And if you split this way, what do you call species whose range expands due to climate change? Are those self-introduced or no due to human influence.
It’s easy to think of species distributions as static boundaries within which a species may be established, but these boundaries are changing all the time. Obviously some species are more mobile than others and some have certain biotic requirements that effectively prevent establishment in certain areas. But barring that, there is nothing stopping a species from just picking up and going somewhere else, especially with climate and other factors as a driving force. “Self-introduced” is not a thing, what you refer to is simply natural range expansion/fluctuation and it is happening constantly. iNat is a useful tool for monitoring such changes in distribution patterns over time, but I don’t think we should explicitly label these things.
I’d just add that a great deal of work has gone on at the international level to try to standardise terminology in this area. See the Global Invasive Species Database for more (especially “provenance/status”):
If any new suggestions cleanly map as subcategories under the { native , alien , cryptogenic (i.e. “we don’t know”) , unspecified } categories, there’s probably no issue, but I’d strongly recommend starting with this conceptual framework before digging further.
Note that the Global Register of Introduced and Invasive Species also includes a category of “native/alien” to cover the fact that some species are native in part of a territory and alien in another part: http://griis.org/.
On the whole, it’s much more useful for us to manage this information at the level of checklists rather than on a per-observation basis, since the variability in recording makes the latter almost unusable at scale.
I think I agree with all the thoughts here on a self-introduced category, since it can be very hard to properly define it and there’s a heavy gray area. But would reintroduced still work as a valid establishment means?