In search of the delicate flapwort—and why we need tricorders

The following piece appeared as a guest post on the Guardian’s GrrlScientist blog on 27th August 2013.

Until six years ago, the only two mosses I could identify with any degree of confidence were Kate and Sir Stirling. Then, intrigued by the delicate ‘spore spikes’ on a hummock of moss I’d spotted on my garden wall, I did some trawling, and tentatively identified the organism in question as wall screw-moss (Tortula muralis). A couple of years later, a commenter on one of my Flickr photos pointed out that the geodesic-patterned ‘sphagnum moss’ I’d photographed on my local moor was, in fact, Polytrichum commune, the common haircap moss. In the space of two short years, my inexpertise in mosses had doubled.

For someone who’s been taking walks on the same Yorkshire moor for over two decades, I’m pretty clueless when it comes to moss. The place is literally made of the stuff: no moss, no peat; no peat, no moor. So, when GrrlScientist suggested I might like to field-test a new book on mosses that she had recently reviewed, I thought it would be an ideal opportunity to start filling the shameful gap in my knowledge.

The book duly arrived in the post. GrrlScientist was right: it’s beautifully produced and illustrated. But then the title sunk in: England’s Rare Mosses and Liverworts: Their History, Ecology, and Conservation by Ron D. Porley. It was the word ‘rare’ that worried me. How rare, exactly? I struggle to identify sphagnum moss in the middle of a moor; what chance did I have searching for rarities?

But then, leafing through the book, I came to the section on the delightfully (and double-entendrously) named delicate flapwort (Solenostoma caespiticium), and read the following:

Several records were made in SW Yorkshire in the mid-1940s by, amongst others, H. Walsh (1881–1962). HW had his ‘eye in’ for the plant and found it in reasonable quantity in the Calderdale area, and by the mid-1950s had found it in about 13 localities (Walsh, 1957). T.L. Blockeel found it at Blake Dean in 1978…

Blake Dean! I know Blake Dean! It’s a local beauty spot, just a couple of miles from my house. Porley continues:

Since S. caespiticium had not been seen for ten years or more it was not eligible for inclusion on the UK B[iodiversity] A[ction] P[lan]; consequently there are no explicit conservation actions. […] Targeted survey of historic sites, particularly within the Calderdale area, is a priority.

Wow! Somewhere on my local patch is seen as a priority survey site for a rare liverwort: it was like a call to arms. Count me in! Now all I needed to do was find out what the hell a liverwort might be.

Liverworts, it turns out, might well have been the very first land plants, appearing on the eastern shores of Gondwana in the early Paleozoic, 543–248 million years ago. Like mosses and hornworts, they reproduce asexually and/or by sending out spores, often alternating between these two modes of reproduction in different generations. There are, according to Porley, 292 British species of liverwort and, as far as I can tell, every single one of them might easily be mistaken for one or other of the 752 British mosses. To we uninitiated, mosses and liverworts look pretty alike. But what the hell? Time to head off to Blake Dean in search of the long-lost delicate flapwort…

Blake Dean
Blake Dean.

It gets off to a bad start. Raising my camera to photograph the upper reaches of Hebden Water as it flows through Blake Dean towards the Hardcastle Crags and down into Hebden Bridge, I somehow contrive to send my sunglasses spinning into the river. There’s nobody watching, so I take off my sandals, wade in up to my knees, and grope around in the dark waters with toes. Contrary to expectation, I somehow manage to retrieve the damn things.

Porley suggests that the delicate flapwort’s rarity might be partly due to its ‘preference for impermanent niches and intolerance of competition’, so I decide my best bet is to look for some recently disturbed ground. I follow the river downstream, but pretty much everywhere is covered in thick clumps of bracken and heather. Then, pausing to photograph the stone bases of the former, ridiculously tall narrow-gauge railway trestle bridge built across the dean during the construction of two nearby reservoirs, I spot a couple of precarious landslides on the far side of the river: the perfect habitat, surely, for Solenostoma caespiticium.

Fortunately, someone has built a small dam across the river just below the remains of the bridge, so I wade into the water once again. I keep my sandals on this time, using the stones of the dam to steady myself—narrowly avoiding grabbing the rock covered in dipper shit in the process.

Site of the old trestle bridge, Blake Dean (note the small landslide).

What sort of person goes wading through rivers in search of mosses and liverworts? Apart from me, I mean. The likes of Ron D. Porley, H. Walsh, and T.L. Blockeel, I’ll bet: unsung heroes of science, in my book. Mosses and liverworts are never going to be as sexy as mammals and birds. They don’t even have flowers, for Pete’s sake. But somebody needs to take an interest in them, to count how many species we’ve got, to work out which ones might be in trouble. These are exactly the sort of people Charles Darwin used to pump for information: non-professional scientists, mostly; enthusiasts; people who know everything that needs to be known about species that nobody else gives a damn about. It’s hardly surprising Darwin got on so well with them: he was one of their number, the consummate barnacle man. (He was also pretty good on beetles, orchids and earthworms.)

I haul myself out of the river, and climb towards the nearest landslide. There’s scree, mud, and heather roots. There are unidentified shoots. There is moss. But there are no liverworts, as far as I can tell—unless some of the ‘moss’ is actually liverworts in disguise, which wouldn’t surprise me. But there’s nothing even vaguely resembling the photographs of delicate flapwort to be found on p.164 of my guide.

Would I even recognise it if I saw it, Solenostoma caespiticium? Not for certain. But I like to think I’d know it was sufficiently similar to what I’m looking for to be worth photographing. Even Porley says the plant closely resembles two other liverworts. These aren’t covered in his book, so I guess they’re not so rare.

Ignoring the Danger sign—I speak literally, not figuratively—I clamber up the overgrown rubble at the side of the former bridge, then back down to the riverbank on the far side. Other people have been this way, but there’s no path worthy of the name, so I make my way into the undergrowth towards a second landslide I spotted from the other side of the river.

How do you get people to worry about the moss and liverwort situation? Is there even a ‘situation’ to be worried about? Porley’s book identifies 84 threatened species in England, but he rightly points out that we need to understand what we mean when we describe a species as ‘a rarity’. Some species are naturally rare, others have rarity thrust upon them. The delicate flapwort is at the southern limit of its European range in England. Perhaps climate change has driven it north. Or perhaps habitat loss is to blame for its rarity. Or modern farming practices. Or maybe it’s always struggled against the competition. Or maybe some combination of these explanations. Unlike with the far more newsworthy English hen harrier, the reason(s) why certain English mosses’ and liverworts’ seem to be becoming rarer isn’t at all clear-cut.

I force my way through increasingly tall and dense bracken. It’s above my head now: hardly the clear ground I’m looking for. I begin to think I must have missed the second landslide, but here it is. Bilberry shoots, uprooted heather, and moss. But still nothing remotely resembling my liverwort. I decide to head on further into the bracken.

The physicist Ernest Rutherford was famously patronising about branches of science other than his own, claiming that all science is either physics or stamp collecting. He probably had biological field scientists most in mind: what else is traipsing about the countryside looking for beetles and mosses, if not a glorified form of stamp-collecting? Piss off, Rutherford! Those people are gathering raw data. To do proper science, you need to measure stuff. It might involve getting your sandals wet occasionally, but people who classify and count species are the biological equivalent of the large hadron collider—and a hell of a lot cheaper.

It seems to me, for a fraction of one percent of the price of a large hadron collider, we could move a whole lot closer to the dream of a hand-held, DNA-assisted, species identification device. A biological tricorder, if you will. At the moment, the idea is science fiction, but DNA-barcoding is getting cheaper and quicker all the time. My friend Karen James and other scientists are already trying to involve the public in scientific research, using DNA barcoding techniques to help assess local biodiversity. Beam me down, I say. In this day and age, well-meaning but clueless individuals like me shouldn’t have to rely on wonderful guidebooks like Porley’s to try to identify arcane species; we need tricorders! Then we can all go searching for rare liverworts.

The bracken is becoming impassable. This is ridiculous. I should have brought a machete. Meanwhile, hundreds of bitey insects have begun feasting on my legs. Time to beat an undignified retreat and have a brew. Mission aborted. Results inconclusive. But at least I gave it a shot. I fight my way back to the remains of the bridge, and re-cross the river, once again using the dam for support.

Eew! I’d forgotten all about the dipper shit!

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