Making the Invisible Visible: Lichens and Air Pollution

Frances Stokeley, TCV Trainee at the Botanic Gardens, led 12 Wild Reekians in a workshop to learn how to use lichens to run a survey on air pollution. We met at St John's Church at the west end of Princes Street to see what we could find out about the air quality in the area.

We began underneath the church, out of the way of the mixed March weather, and got stuck in to examining lichens.

Frances gave us an information-packed presentation including air monitoring stations in Edinburgh:

How lichens grow and diversify in cleaner air:

A visual demonstration of the structure of lichen: the substrate such as a tree or rock (left), the photosynthesising algae producing food (centre), and the fungus providing shelter and structure (right):

The biodiversity value of lichen, from Tardigrades to Reindeer, Stick-insects camoflage to birds' nests:

Then we got down to using hand-lenses to examine the different structures of lichens which grow on trees

To find ways to describe them with made-up "common names" - the best was "Washed-out black horned splat lichen".

And to classify them into crusty (left), leafy (centre), and bushy (right):

Outdoors, we discussed air pollution, especially particulate pollution which is far smaller than the width of a hair (yep I was so busy taking the photo I didn't write down the statistic). Poor air quality causes a huge range of health problems for us, and shortens lifespan significantly.

Lichens are particularly sensitive to pollution, as they have no skin like a plant or animal, but absorb everything directly from the air around them. And, in a low-lying, sheltered corner below Lothian Road and Princes Street, we didn't find a single crusty, leafy or bushy lichen in St John's Churchyard. There is plenty of work to be done on air quality at the West End of Edinburgh.

However, nearby in West Princes Street Gardens, slightly further from Lothian Road and less sheltered by walls so there was more air movement, we did find plenty of crusty lichens on the trees. This showed both how useful the technique was and what a difference air quality made to lichen biodiversity over a very short distance.

Frances sent us away with a challenge to take the Lichen Pledge, to take some action on improving air quality for lichens and for us. There are all kinds of things one could do, perhaps most importantly to pass on the knowledge we gained by taking a local group to survey lichen in another part of the city. My suggested challenge, as organiser of Wild Reekie and co-ordinator of the Wildlife Proclamation campaign, is to come along to our Elections Nature Café on 6 April, tell our prospective MSPs about the connection between lichen and air pollution, and make sure your they have signed the Wildlife Proclamation: “If elected I undertake to work to restore Scotland’s nature.”

Huge thanks to Frances for running a brilliant workshop. We were privileged to be the first group to experience it: she has a few more coming up so catch them if you can! Email her at F.Stoakley@rbge.ac.uk if you would like details of when these are.

"Thank you Frances, your knowledge, enthusiasm and doability is a joy to behold. I'm fired up for the survey, and intend to help stoke up local concern."

"Really enjoyed that, and will help me share my interest with others. I can also do the survey locally and feed it into a growing concern locally about air pollution."

Follow the Wild Reekie Meetup group for details of future events. You can follow Eleanor Harris on twitter @eleanormharris. 

Discovering Moss on Blackford Hill

Following our first foray into bryology in January, Wild Reekie and Edinburgh Bryophyte Recorder David Chamberlain went out again to Blackford Hill in search of mosses and liverworts. This time we were armed with hand-lenses, to delve deep into the miniature world of moss...

1. Tortula muralis (Wall screw-moss)

2. Grimmia pulvinata (Grey-cushioned grimmia), with distinctive grey fur to catch water.

Grimmia pulvinata (Photo by Olesya)

3. Bryum capillare (Capillary thread-moss), with bright red setae (stalks) and bright green capsules.

Bryum Capillare (Photo by Olesya)

4. Orthotricum anomalum (Anomalous bristle-moss)

These first four wall-mosses were the only species which had stuck in my head after our previous excursion, as I'd seen them on walls all over Edinburgh. And indeed, we saw all of them on the wall of the Blackford Hill Observatory car park. They are good for beginners.

5. Didymodon rigidulus (Rigid beard-moss) is another common wall species.

6. Brachythecium rubatulum (Rough-stalked feather-moss) was the first pleurocarp moss we saw, with long, straggly, branching stems. The first four are all Acrocarp, with one capsule coming out of one upright stem.

7. Brachythecium populeum (Matted feather-moss) is an indicator of high pH, and therefore grows on the lime mortar in walls.

Moss often grows on the mortar in a wall. Wall-stones are usually quite hard and smooth, and difficult for moss to get a hold or find moisture; whereas natural rock is usually cracked and weathered and therefore covered in moss. The basalt outcrops of Blackford Hill are a good example of this.

We found the straggly pleurocarp mosses

8. Rhytidiadelphus squarrosus (Springy turf-moss) and

9. Pseudoscleropodium purum (Neat feather-moss)

both growing in the turf under a tree. Rhytidiadelphus squarrosus is a notorious nuisance in lawns and looks a bit like pipe-cleaners. Scheropodium purum needs a lot of light to flourish, and has a more juicy, succulent appearance.

Succulent Scheropodium purum (left) and bristly Rhytidiadelphus squarrosus (right)

10. Bryum radiculosum (Wall thread-moss) is one of many mosses with an ingenious method of reproduction: it has tiny tubers or potatoes on its roots which can grow a new plant if they dry out and blow away.

11. Barbula convoluta (Lesser bird's-claw beard-moss)

12. Syntrichia ruraliformis (Sand-hill screw-moss)

13. Porella platyphylla (Wall scalewort) was our first liverwort

Porella platyphylla

14. Amblystegium serpens (Creeping feather-moss)

Amblystegium serpens

Then we had some examples of a varied colony of moss on a rocky basalt boulder.

15. Bryoerythrophyllum recurvirostrum (Red beard-moss) has a bright, stellate appearance and turns red when mature

Bryoerythrophyllum recurvirostrum

16. Schistidium apocarpum (Sessile grimmia) has a smart black base and red capsules with no stalk.

17. Orthotricum rupestre (Rock bristle-moss) is stragglier than the Orthotricum anomalum we saw earlier, and has hairy capsules as if it was wearing alpaca hats, which distinguishes it from Orthotricum cupulatum which has smooth hats.

David's "apprentice" Steve demonstrating his ability to distinguish between these different types of Orthotricum.

We then saw two more Orthotricum mosses on a nearby tree overhanging the Braid Burn,

18. Orthotricum diaphanum (White-tipped bristle-moss)

19. Orthotricum pulchellum (Elegant bristle-moss)

Orthotricum pulcellum

The tree was also home to liverworts:

20 Metzgeria furcata (Forked veilwort) is a thallose liverwort which means it forms a flat, thin plate against the tree

21. Frullania dilatata (Dilated scalewort) looks like a brown blob on the tree, until you look closely through the lens and discover its intricate structure:

Frullania dilatata

The next set we found in the woods of the Hermitage.

22. Pseudotaxiphyllum elegans (Elegant silk-moss) which is tolerant of both shade and higher pH

23. Isothecium mysuroides (Mouse-tail moss)

Pseudotaxiphyllum elegans and Isothecium mysuroides

Someone asked whether moss was any good to eat. The answer is no, it is almost completely unnutritious, which it perhaps evolved as an evolutionary advantage to avoid being eaten. The only nutritious part, which things do eat, are the capsules full of spores, which like eggs are full of protein. Moss is, however, a habitat for all kinds of tiny creatures like nematodes and tardigrades.

24. Polytrichastrum formosum (Black haircap) which several of us thought was a sphagnum moss (it isn't). Steve had everyone examining its toothed leaves against the light through their hand-lenses...

Polytrichastrum formosum

Examining the toothed leaves of Polytrichastrum formosum

25. Lepidozia reptans (Creeping fingerwort) is a liverwort with four-fingered leaves, although we all struggled to see this even through a hand-lens.

26. Pellia endiviifolia (Endive pellia - if that makes you any the wiser!), another liverwort, has little chimneys in its complex structure to regulate its own atmosphere.

27. Kindbergia praelonga (Common feather-moss), which we thought particularly attractive with its delicate and fluffy fronds

Kindbergia praelonga, like a green feather boa

28. Dicranella heteromalla (Silky forklet-moss) is also very attractive with its dark green pincushion and bright red capsules

Dicranella heteromalla

29. Atrichum undulatum (Common smoothcap), which has extraordinary capsules which (the hand-lenses showed us) were like pepper-pots with teeth and a drum over the top.

I don't know about everyone else but I'm hooked - and I've bought the book! It's a very well-designed field guide which leads the absolute beginner like me gently into the magical world of moss. Copies available from David.

Huge thanks to David and Steve for an inspirational day. You can follow - and join in - the future adventures of Wild Reekie at www.meetup.com/Wild-Reekie.

Eleanor Harris

Fun with hand-lenses (Photos by Alex)