If I told you that during a 200m walk down a suburban London street I saw 13 different species from one group of organisms, you might struggle to imagine what I could have seen. You’d probably be even more surprised to learn that this significant diversity belongs to one of our most unassuming plant groups: the mosses.
Even as an unashamed plant enthusiast and keen botanist, I’ve always struggled to get my head around mosses. How can it be possible to tell apart such tiny and uniform plants? Or so I thought. A fantastic week on the Natural History Museum’s plant taxonomy and identification course was an even more eye-opening experience than I could ever have imagined!
What is moss?
Mosses belong to the group of plants called bryophytes, which consists of mosses, liverworts and hornworts. Bryophytes are the most primitive group of land plants, and arrived on land around 500 million years ago. They are located at the root of the land plant tree and display many ancient plant features.
Bryophytes evolved in a hostile environment, and this explains many of the primitive characteristics that they display today. They follow a poikilohydric lifestyle, i.e. they dehydrate and rehydrate depending on environmental water conditions, and lack a vascular water transport system. However, this primitive life-history strategy allows them to inhabit and colonise many extreme and marginal habitats, from the cracks in the pavement to deserts. Arriving on the uninhabited rocky surfaces of the Earth’s landmasses 500 million years ago, bryophytes were the first step in the formation of soils and the ensuing diversity of terrestrial life that we see today
How can I tell different species apart?
I had always pictured bryophytes as an uncharismatic group of plants, far too small and uniform for me to even consider identifying. However, the closer I look the more I realise how distinct each species is. Navigating around the morphological features of any moss, with their relatively simple structure, and matching each specimen to its species description in a field guide is far easier than I imagined. In fact, I now realise that around 95% of the mosses are easily identifiable in the field with the help of a hand lens. Although a closer look under the microscope is an added bonus, allowing a detailed view of the intricate features of each moss.
The beauty of moss is that specimens are easily stored, and a successful field trip can form the basis of a reference collection for future use. Rehydration of a dried moss specimen is almost instantaneous, bringing the features and structure back into sharp focus for closer examination from the comfort of your home.
What is out there, where can I find them and why do mosses matter?
Any budding bryologist will be enthused to hear that mosses are pretty ubiquitous, and even in an ecologically unpromising location you can be sure to find several different species. Growing on walls, pavements, trees, and in most lawns, a handful of the commonest moss species can become familiar friends after only a few field visits. Travel further afield, and things only get more exciting: from bog-loving Sphagnum to star shaped Polytrichum up to 40cm tall, the UK has over 700 mosses just waiting to be discovered. And, as if you needed any further convincing that mosses are awesome, exciting and amazing, 20-30% of the world’s carbon stores are currently locked up in Sphagnum dominated peat bog.
Getting into bryology
If you have been inspired to get out and identify some mosses yourself, the British Bryological Society website provides some excellent resources and tips for beginners. Any aspiring bryologist should consider purchasing a copy of their field guide: Mosses and Liverworts of Britain and Ireland, A Field Guide (I.Atherton, S.Bosanquet, M.Lawley). The best place to start is in your own garden or street, and once you become familiar with the common mosses to be found near to your home, you can venture further afield to explore the UK’s wider diversity.
Morris, J. L., Puttick, M. N., Clark, J. W., Edwards, D., Kenrick, P., Pressel, S., … Donoghue, P. C. J. (2018). The timescale of early land plant evolution. Proceedings of the National Academy of Sciences, 115(10), E2274–E2283. https://doi.org/10.1073/pnas.1719588115
Freeman, C., Evans, C. D., Monteith, D. T., Reynolds, B., & Fenner, N. (2001). Export of organic carbon from peat soils. Nature, 412(6849), 785–785. https://doi.org/10.1038/35090628