Why iNaturalist observations without photos can be research grade

I’ve written before about how iNaturalist, at least most of it, is essentially a huge, extraordinary, online natural history museum. Instead of specimens, it’s got photos and sound recordings. There is an emphasis, both in the user interface and the iNat community, on collecting what’s described as evidence-based observations. The evidence is a photo or audio recording. Other users, often with considerable expertise, can use this evidence to confirm identifications, and so make them “research grade”.

This has led to some iNat users questioning whether there is any use to uploading observations without supporting evidence. On a recent discussion on the iNaturalist forum, some users were of the clear view that such observations are second class citizens in iNaturalist and should be discouraged.

I want to push back against this view that citizen science observations without evidence are unlikely to be of use for research. Often that’s not true.

To do research with biodiversity data, it is ideal to estimate the probability that an observation ID is correct. With museum and herbarium collection data, it is usually assumed that mis-identifications are unlikely and IDs can be assumed to be correct. That’s not the case with iNat data, whether or not an observation is “research grade”. (We should not be ignoring the mis-identification probability in collections either.)

The probability of an iNat ID being correct can be estimated using a combination of the proportion of times particular observers and particular identifiers have misidentified a particular taxon. Some taxa are also inherently easier to ID than others, which can be quantified with iNat data.

If there’s a “research grade” observation with a photo, it could still have the wrong ID. That probability could be calculated from the frequency with which this species has been misidentified in other iNat observations, and the track record of the observer and identifiers at identifying this species.

If there’s no photo with an observation, the ID can still have a high probability of being correct. That’s when that observer has an excellent track record identifying that species on iNat, especially when that species is infrequently mis-identified generally. These probabilities can be estimated with iNat data.

In other words, for both “research grade” observation and observations without evidence, the probability that the ID is correct can be estimated using iNat data. In both cases, observations with a higher probability of being correctly identified are more useful for research.

We shouldn’t be thinking of each iNat observation sitting alone and independent. For research, it’s just as important to know the context of the demonstrated accuracy of the observers and identifiers.

My view is that we should be encouraging everyone to get outside and make lots of observations of wild species to document the natural world and how it’s changing. That’s with and without photos.

If a particular species is “your thing”, and you have demonstrated on iNat that you are very good at identifying that species, it is counterproductive for us to say that iNat only wants your observations with good photos. I’m worried by the thought that we encourage these users to keep all of their other observations on a spreadsheet on their computer because we tell them that they’re of no use to others. That would be a massive lost opportunity to better document nature.