Biases in iNat data

I interned at Everglades National Park, many years ago, with a scientist who was studying the chironomids of the park. He, an expert, had to go to great lengths to document the features necessary to ID to species. Rearing larvae, keeping and fixing the exuvae, fixing the adults, etc. Surprisingly frequently something turned out to be yet another undescribed species he didn’t have time to describe.

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On that note, I will add a special case in certain tropical regions, such as the Caribbean: Over-representation of anything that lives near resorts (beach taxa, weedy/urban taxa), and under-representation of taxa that live in the interior in non-touristy areas.

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Over-representation of rare, vagrant birds
Under-representation of small, arboreal passerine birds (warblers, etc)
Under-representation of basically anything aquatic, especially marine life, with the possible exception of tidepool organisms in heavily populated areas like California
Under-representation of many highly populated countries where iNaturalist has little presence

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These are all great, but I wonder if it would be quicker to figure out which taxa, in which places, are not over or under represented on iNat. :-)

To do that, all I can think of is the few projects in iNat that are devoted to always looking for all species in a taxonomic group at surveyed sites. Even then, biases in the methods used may detect some species more than others.

(Surveying biodiversity in an unbiased way is hard.)

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Same here! Don’t remember percentages, but Russian iNat started with botanists, so we have more plants to other stuff ratio than other regions. And plants are ided, unlike many other groups.

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You can check Diptera.org, some keys are there, plus people who can help, if they will see your topic over tons of others, but be ready, chironomids require many small parts photographed, so I don’t even look at them now, no need to torture them if id won’t happen anyway.

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I’d say over-representation of wildlife in protected areas, especially a few iconic ones (Yellowstone, Great Barrier Reef…) as compared to non-protected or non-iconic zones, since people are more likely to go there, take pictures and keep archives

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I agree that flowering plants (i.e., plants at flowering stage) are over-represented but I don’t think that’s true of fruiting plants. Just the opposite seems to be true, as evidenced by the algorithm’s general inability to identify fruits. Likewise, plants with flower buds are under-represented.

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Small passerine birds are underrepresented because they never sit still long enough to get a picture!! Either that or they are lurking in the undergrowth, up to no good (@fffffffff).
Tongue planted firmly in cheek.

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Anything that is extremophilic, really.

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Anything that lives underground (today I learned the word “rhizosphere”)

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Over-representation of areas with existing records. People tend to go places where they know they’ll find things. The existing records are a guide.

The converse is also true.

Systematic sampling is hard and often disappointing. Oh, there’s another bias. No negative records in iNat. We only record when we find something. No record of seeking a species and failing.

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We can record absence if we use trips feature btw.

7 trips in 2020, 5 in 2021. I think we can say most taxa have little negative data.

Things that are speedy!

Both on our company account (this one) and my own personal account I am aware that we have a lot more observations of things that grow, or crawl, or perch or swim slowly than things which move rapidly. My own account has no swallows or swifts, despite them being the most abundant birds in my garden.

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I agree. I would guess that there are no taxa that are never over or under represented.

Interesting. What I’ve noticed there is that (for some species) fruits tend to attract observers’ attention, and also to be useful in ID. But certainly it is true that for most species the fruits and buds are not as attention grabbing as the flowers. Do you think there are many plant species that people are less likely to observe when they are fruiting than when they have no reproductive parts showing?

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Because it’s an old feature mostly not used, while fully working! It’s just abandoned by staff as they didn’t want to go that direction.

I can think of quite a few species for which this is true. Pretty much all of the sessile-flowered trilliums are in this category. They emerge early in the spring (when humans are anxious to observe new growth) with conspicuously mottled leaves. The fruit, on the other hand, remain hidden beneath the dried sepals, and are seldom observed.

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Under-representation of anything common
For insects, larger species are much more commonly observed than smaller ones

@mpintar this is so true. I recently became aware of and interested in Macrotera bees. (https://www.inaturalist.org/taxa/252960-Macrotera)
Here’s a crazy comparison: today I saw 30-50 individuals on a short walk in the neighborhood versus 143 total observations in all of iNat.

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