Now so rare, the entire global range of this plant covers only 16cm². It’s also completely endemic (unique) to Cornwall, found today at only two locations in the county and nowhere else in the World. It’s called Cornish Path Moss, or ‘Ditrichum cornumbicum ‘(its Latin/species name) if you have enough time to learn these things.
If you’ve not heard of it before, don’t worry. It was only discovered in 1963, on a roadside/path (hence the name) and was only identified as a separate species in 1976. (It does look very similar to most other mosses too be fair.)
Like all mosses, Cornish Path Moss is a Bryophyte (a family of small plants including Liverworts). It’s evergreen, and only grows up to a couple of centimetres tall. One id feature used to separate it from other species is the leaf arrangement. They’re arranged in segments, like a spinal cord, usually with four-five upwards facing points. Very similar features are found in other species though, so if you’d like to learn how to id it properly, conservation project Back From The Brink are giving people training on how to recognise it.
In most ways, this species is just like other mosses, it needs water to reproduce, derives its energy from the sun, has structures called Rhizoids instead of roots, etc. So why is it so rare? The main reason researchers believe is its very specific habitat. Both of its sites are abandoned Copper Mines. The first, Phoenix United Mine, abandoned after the 19th Century, was a Tin and Copper mine, where mosses and Lichens now flourish. The second, Crow’s Nest (now an SSSI-partly thanks to the Cornish Path Moss) is a Copper Mining Site, abandoned at around 1880, and is home to other scarce mosses such as Pohlia andalusica and Scopelophila cataractae.
Until recently, there was also a third site where Cornish Path Moss was found ironically not in Cornwall, but Mountain Mine in County Cork-Ireland, also an abandoned Copper Mining site.
It lives in only these places, because it needs conditions where the soils are contaminated with certain metals, as they give it certain life-enhancing elements and chemicals it needs to stay healthy.
Because of this love of metallic soils, it’s a good indicator of soil composition, largely invisible when just looking at topsoil. It also means it’s useful at absorbing toxic elements, like Arsenic, which if allowed to contaminate water for extended periods, can cause cancer in humans, so the moss is doing us a favour absorbing it. Like all mosses, although unsuspecting it provides a home for a myriad of organisms naked to the human eye, including:
Tardigrades/Moss Piglets/ Water Bears-About 1mm long, they’re closely related to arthropods, with about 1,000 species of them alive today, living everywhere from the deep sea to inside a lump of Cornish Path Moss.
Rotifers-Tiny animals, they grow to a maximum of 0.5mm, and are fantastic at filtering out water with their row of Cilia. They’re sadly food for most things and live in a mix of fresh and saltwater habitats (including damp mosses).
Nematodes-Small worms, moss-dwelling species are usually microscopic, grazing peacefully on moss and sometimes fungi cells. These aren’t to be confused with the larger species, which grow over a meter-long infesting and consuming the insides of humans...
Despite all its benefits, Cornish Path Moss could go extinct soon if we aren’t careful. Its niche habitat is one of the main reasons it can’t be found in many places, but the main threat to those existing sites being outcompeted by larger mosses, or scrub plants, something which will happen without human intervention.
To stop the decline and ideally expand its range, Back From The Brink are training people to be able to identify the moss, and then go out on surveys to monitor the current population and it’s trends.
More research on the makeup of the soils they live on is also very important, since not much is known still, and with more information, other sites could be selected for possible reintroductions etc. The exiting possibility of undiscovered sites is very real too! Perhaps it grows in some remote place in another country but goes by another name? Or maybe there’re hundreds more sites scattered round Britain that just haven’t been discovered yet?
If you’d like to find out more on this mysterious little species, I’ve stuck some useful links here:
Back From The Brink: https://naturebftb.co.uk/the-projects/cornish-path-moss/#:~:text=What%20is%20Cornish%20Path%20Moss%3F%20This%20unusual%20plant,are%20the%20only%20known%20sites%20in%20the%20world.
Wikipedia (if you trust it!): https://en.wikipedia.org/wiki/Ditrichum_cornubicum
Natural History Museum: https://www.nhm.ac.uk/our-science/data/uk-species/species/ditrichum_cornubicum.html
National Biodiversity Network: https://species.nbnatlas.org/species/NBNSYS0000036168
Blog with more info: https://www.bloomindoom.com/environment/hidden-worlds-in-search-of-cornish-path-moss
Thanks so much for reading! :)
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