In my time curating the Cnidaria observations on iNaturalist, I’ve noticed some peculiar aberrations in the participation rate of certain regions.
I’m going to attempt to illustrate what I mean by highlighting the family Actiniidae. These are the most common and diverse sea anemones in coastal habitats, meaning that these are easily observed by casual users, thus not requiring any scuba equipment. I’ve chosen to examine a mix of regions, both in terms of ecology and population. The following chart indicates the number of observations per month.
119 / 444 / 559 / 022 / 037 / 0286 / 3730 / 104 / 011 / 009 / 012 January
123 / 264 / 292 / 029 / 022 / 0379 / 3801 / 098 / 008 / 009 / 010 February
140 / 185 / 287 / 025 / 058 / 0438 / 4015 / 111 / 003 / 020 / 006 March
949 / 302 / 309 / 008 / 033 / 0758 / 4726 / 061 / 012 / 067 / 010 April
791 / 445 / 229 / 017 / 051 / 0954 / 4653 / 070 / 012 / 038 / 006 May
109 / 191 / 227 / 017 / 080 / 0912 / 8243 / 033 / 026 / 031 / 020 June
134 / 251 / 246 / 012 / 066 / 1593 / 5268 / 016 / 031 / 047 / 003 July
131 / 294 / 319 / 014 / 062 / 1783 / 3630 / 038 / 024 / 020 / 011 August
152 / 348 / 380 / 004 / 027 / 0948 / 2362 / 054 / 010 / 023 / 024 September
288 / 416 / 491 / 003 / 027 / 0804 / 2490 / 114 / 001 / 026 / 021 October
175 / 315 / 415 / 005 / 026 / 0345 / 3641 / 191 / 008 / 020 / 026 November
208 / 388 / 566 / 023 / 049 / 0318 / 3816 / 140 / 013 / 009 / 015 December
South Africa (12 species; tropical & subtropical): South Africa has an interesting mix of tropical and subtropical species (even becoming somewhat temperate around Cape Town, with species like Bunodosoma capensis). However, only 4.6% of the observations come from the tropical and subtropical region (i.e. Aliwal Shoals to KwaZulu-Natal). There is a relatively low, but steady, participation throughout the year, but with a MASSIVE uptick during the City Nature Challenge (CNC), largely thanks to Cape Town and Durban. I tend to get very bored identifying this fauna between April and May, when I’m hit with a large volume of the same 4 species.
4.65 observations per observer / 16.93 observations per identifier
Actiniidae : Actiniaria ratio = 83.5%
New Zealand (14 species; subtropical): Very consistent participation, at roughly twice the volume as South Africa, with minimal seasonal variation and a minor uptick during CNC.
5.82 observations per observer / 24.67 observations per identifier
Actiniidae : Actiniaria ratio = 73.6%
Southern Australia (16 species; tropical & subtropical): Similar to New Zealand, but without any bump from CNC.
4.25 observations per observer / 16.11 observations per identifier
Actiniidae : Actiniaria ratio = 79.4%
Japan (23 species; tropical, subtropical, & temperate): This data also includes South Korea, as well as the tropical fauna of the Ryukyu Islands, minus 2 observations from Hokkaido that didn’t fit within the map box. Minimal participation throughout the year. CNC is a non-factor.
2.98 observations per observer / 9.94 observations per identifier
Actiniidae : Actiniaria ratio = 66.7%
SE USA (5+ species; tropical & subtropical): Texas to North Carolina, with a few Bahamian observations that snuck into the map box. Participation is minimal throughout the year—slightly more than Japan, but about half the volume as South Africa.
1.69 observations per observer / 5.06 observations per identifier
Actiniidae : Actiniaria ratio = 45.4%
Europe (22 species; subtropical & temperate): This is the Northeast Atlantic and Mediterranean, minus Iceland and the Canary Islands. Participation is similar in volume to New Zealand and Australia during their respective winters, but MUCH higher during the summer. Europe clearly likes to holiday.
2.60 observations per observer / 13.95 observations per identifier
Actiniidae : Actiniaria ratio = 73.2%
West USA (17 species; subtropical & temperate): Vancouver to San Diego. Y’all are really into sea anemones over there. There’s little seasonal variation, and no obvious CNC bump, but the CalCoast BioBlitz is evident in June. Does that sound correct? Honestly, very surprised that the CNC bump doesn’t show itself here.
3.55 observations per observer / 27.48 observations per identifier
Actiniidae : Actiniaria ratio = 89.8%
India (11 species; tropical): Most observations (91%) are from a relatively small stretch of the coast, between Mumbai and Goa, and another 4.6% by Visakhapatnam on the east coast. The geographical breakdown is intriguing, as Kolkata and Chennai are poorly represented. The former sits on a river delta, which is poor habitat for actiniids. I’m not sure if there’s an ecological explanation for Chennai. Monsoon season is April-September, which is clearly evident in the data, but otherwise the volume is moderate, similar to South Africa, without any CNC bump.
6.82 observations per observer / 14.10 observations per identifier
Actiniidae : Actiniaria ratio = 80.9%
Singapore (9 species; tropical): Participation is, per capita, quite high, and nearly equal to (88%) Japan’s total volume. Climate plays a notable factor. During the cooler, drier periods associated with the Southwest Monsoon, observations increase. The downturn in October is also associated with a warming intermonsoonal period. CNC doesn’t see an uptick, likely due to the inopportune weather.
3.95 observations per observer / 12.23 observations per identifier
Actiniidae : Actiniaria ratio = 15.2%
Hong Kong (14 species; tropical & subtropical): Participation is, per capita, quite high, and nearly double (178%) Japan’s total volume. During their relatively mild winter, observations decrease noticeably, and there’s a slight uptick during CNC.
3.46 observations per observer / 8.17 observations per identifier
Actiniidae : Actiniaria ratio = 46.4%
New Caledonia (8 species; tropical): Participation is, per capita, quite high, and nearly equal to (91%) Japan’s total volume. In fact, if we factor in all of Actiniaria, New Caledonia has 227% as many observations as Japan and South Korea combined, despite having just 1.5% of their population! There’s little indication of any seasonal or CNC variation.
7.45 observations per observer / 20.5 observations per identifier
Actiniidae : Actiniaria ratio = 26.8%
I began this investigation with a couple major questions.
- Does the enormous drop in observations seen in South Africa following the City Nature Challenge occur in any other region?
- How does the volume of observations from Japan compare to other regions?
Answer: surprisingly low.
But in putting together this data, I was struck with some other curious findings…
Europeans love to photograph sea anemones during their summer holiday. Seriously, you don’t see this trend anywhere else. Is this what they do in Europe on their holiday?
Also interesting is how different the total volume of observations is when comparing the Western and Southeastern USA. Clearly this relates to the abundance and diversity of species in these regions. Coastal ecosystems are replete with sea anemones out West, but they’re mostly a non-factor in the Southeast. But if we compare the Southeast to other corners of the globe, I think there’s a general lack of participation, particularly if we exclude the tropical Florida fauna from this equation. Coastal ecosystems of the Southeast are still very poorly represented on iNaturalist.
I want to give a special shoutout to the Indian iNaturalists (particularly @pradip @shaunak @ajamalabad), who’ve done such an exemplary job of documenting their fauna, both in terms of quantity and quality of their observations. Plenty of interesting discoveries have been made here, including some major range expansions documented for the first time. It’d be great if all coastal ecosystems had such a dedicated community of naturalists.
There are some ecological peculiarities revealed when comparing the faunal ratio of the family Actiniidae to the order Actiniaria. This family is generally the dominant sea anemone group in intertidal habitats, especially in cooler regions, but the data shown here is also artificially influenced by the current (and largely outdated) system of classification used for this group. For instance, in Singapore, this ratio was a meager 15%, but this is largely due to the fact that some of the more common actiniid-like anemones (e.g. Heteractis, Stichodactyla, Phymanthus) have been questionably placed into separate families, all closely related. If we factor this in by comparing the superfamily:order ratio, we get a more typical 77.2%. This is true throughout the tropics, which is why we see a similar phenomenon in New Caledonia, but there’s also a sociological factor at play. In India, where most observations are from tidepooling (rather than scuba or snorkel), the observations skew away from certain non-actiniids found at greater depths.
Another special mention is warranted for the small but dedicated group of iNaturalists in New Caledonia (particularly @damienbr @pl_stenger @juju98 @clairegoiran @jeanro), who have done such a tremendous job documenting their coral communities. The average of ~8 observations per observer puts to shame most other regions. Compare this to the 1.69 average seen in the Southeast USA, where the #2 most prolific observer trails the #8 most prolific observer in New Caledonia, despite that region having only 51% as many observations. Though to be fair, the fauna is significantly less diverse in the Southeast.
I’d be curious to see a modal breakdown of observations per identifier for these regions, but I’m far too lazy to crunch the numbers. I suspect the mean data shown here is largely influenced by a very small number of users, but this number probably varies based on the user base of each region. Myself and @phelsumas4life are by far the most prolific in this respect, accounting for nearly all identifications in some areas (looking at you, SE USA). One way to compare the relative quality and efficacy of the local identifiers is to see how many have accounted for at least 5% of their local identifications (i.e. dividing user identifications by total observations). For the purposes of this, I’ll expand the data to include all of Actiniaria: South Africa (5/209) / New Zealand (7/181) / Australia (6/301) / Japan (3/31) / SE USA (2/168) / Europe (4/750) / West USA (4/1907) / India (4/89) / Singapore (4/39) / Hong Kong (4/60) / New Caledonia (3/19). Thus, of the 209 users who have identified South African sea anemones, only 5 have been active enough to identify at least 5% of the total number of South African sea anemone observations. The only regions where I’m not the leading identifier are the West Coast (ranked a pedestrian #13) and New Zealand (#2, behind @tony_wills).
Lastly, Japan. I’ve always been perplexed by the relative lack of iNaturalist engagement from this country. One could be forgiven for thinking there might be some sociological explanation for this—maybe the Japanese simply don’t interact much with nature? But nothing could be further from the truth. Japanese divers are some of the most prolific in the world at documenting their marinelife, they simply don’t do it here. It’d be great to see this participation rate improve through a bit more outreach. I really can’t emphasize enough how anomalous this is.
Anywho, that’s all I’ve got. Hope you enjoyed the data, nerds. I’d love to see more analysis like this from the statisticians at iNaturalist.