Who makes these IUCN range maps!?

Nature Talk
1

So, let us take Macrobrachium rosenbergii, the giant river prawn we all know and love.

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Here are it’s gbif occurrences.

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Here are the inaturalist occurrences and and predicted range from the geomodel.

Now, the IUCN, a respected institution. What do they say is the range of the giant river prawn?

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Somehow, they managed to create this abomination of a range map. Where do I even begin? It includes literally all of China, including the vast deserts, mountains, and boreal/subarctic forests of Xinjiang, Tibet, Inner Mongolia, and Manchuria, as well as the temperate regions of northern and central China. This is in spite of this species only possibly ranging into the most extreme south of China. It also includes the vast bulk of India and Pakistan, despite being only present in the humid tropical areas of southern and eastern India. On the flip side, it straight up excludes New Guinea, Australia, Taiwan, Vietnam, Laos, and all of Indonesia except Java, despite the species living there. You may argue, well they have to following political borders! To which I respond, no they don’t. Political borders are a TERRIBLE way to map the range of a species because they don’t correspond to ecological reality. But even IF you insisted on using them, this map STILL fails. Because it excluded several countries where the shrimp lives, and it arbitrarily only included Java while leaving out the rest of Indonesia. It also excludes some parts of India and Pakistan.

If you truly had to use political borders, the map would look like this

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It still sucks, but it’s way better than map they have.

So I decided to look into the bibliography of the IUCN page for this species. Here is what their sources say.

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Taken from: Holthuis, L.B. 1980. FAO Species catalogue. Vol. 1. Shrimps and prawns of the world. An annotated catalogue of species of interest to fisheries. FAO, Rome.

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Taken from: Silva-Oliviera, G.C., Ready, J.S., Iketani, G., Bastos, S., Gomes, G., Samapaio, I. and Macie, C.l. 2011. The invasive status of Macrobrachium rosenbergii (De Man, 1879) in Northern Brazil, with an estimation of areas at risk globally. Aquatic Invasions 6: 319-328.

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Taken from: 1. Wowor, D. and Ng, P.K.L. 2007. The giant freshwater prawns of the Macrobrachium rosenbergii species group (Crustacea: Decapoda: Caridea: Palaemonidae). Raffles Bulletin of Zoology 55: 321-336.

So they straight up ignored/didn’t follow THEIR OWN SOURCES.

So, to you all, I simply ask. How could this atrocious range map have possibly passed quality control?

2 Likes
2

Sounds like a question for IUCN.

5 Likes
3

Looking over the sources again, there is something quite interesting. One of their sources was a taxonomic revision of the genus Macrobrachium, where all the occurrences east of the Huxley’s line is split off from M. rosenbergii, as a distinct species, M. dacqueti. So not only does this make the original IUCN map even more hilariously wrong, it actually makes all of those inat observations and gbif occurrences of M. rosenbergii, on mainland asia and west indonesia wrong now as well.

Life is both a comedy and a tragedy

4

The species is expanding its range due to humans cultivating the species for food. so the maps may not be that accurate. A fast check indicates that the species is spotted somewhere in Africa in the wild. The population may establish itself or it may not.
It is a tropical species living in brackish waters to freshwater. I’ve watched a few youtube vids of some indonesians fishing for this prawn in their rivers. The species is frequently farmed. It can reach a large size. I doubt its ability to survive the cold winter of temperate regions but I didn’t check. Its production may happen in indoor farms or outdoor grow out ponds. There are places on earth with lots of land. It may be present in Australia.

5

This is a pretty clear cut case. It lives natively in the Philippines, eastern Indonesia, New Guinea and Australia. Even before the taxonomic revision, the iucn map was just so hilariously wrong, and the taxonomic split made it even wronger