Blog of the International Association of Bryologists: Why study moss?

Wild green wall. Punta Arenas, Chile

On the few occasions someone has pointed a microphone at me and asked why I 'chose to study moss', I've found myself struggling to respond. I imagine they expect a heroic answer, like when people say they wanted to be an astronaut since a child, or experienced an epiphany and felt drawn to a life on stage!

Now that I stop to think about it, I stumbled upon moss possibly in much the same way others have found themselves studying this tiny – but important and fascinating – plant.

My path took a mossy turn as I contemplated a PhD in Australia after an undergraduate degree in biology, topped by an Honours project in conservation genetics on a rare native plant. To assess potential PhD projects, I drew up a list of criteria that included, amongst others, developing new skills; a friendly lab or research group; and potential for an experimental approach.

I didn't really mind what taxa it was, but I happily settled on a moss project that fit the bill – tweaking and nipping it until it was my own. The starting point was the potential for mossy biocrusts on green roofs, but I felt not enough was known about how moss survives more generally in the urban environment, so I back-pedalled a little. City life involves changes in light, hydrology, pollution and substrate. How do these effect the biodiversity of moss? Now that I'm firmly focused on moss, there are many reasons I enjoy studying it.

My colleague, Flavia Ferrari from Brazil keeps her distance from the wild life while recording moss communities on King George Island

I like the way moss makes me think about concepts like scale, water relations and surviving stresses. The fact it is so small, and its leaves just one cell thick, means it can rely on the process of diffusion to obtain water and minerals. This in turn affects where it thrives - particularly in the urban environment where it can exploit small niches like pavement cracks, dimples in road surfaces or skeletal soils. Rhizoids suffice where larger plants require the vascular tissues of roots.

Desiccation tolerance - described as the ability to dry without dying – is surely one of the most amazing qualities of bryophytes, found in different degrees among these plants. It involves a carefully choreographed sequence of events, where plant sugars create glass-like coverings that protect macromolecules like DNA or proteins, which would otherwise crack and crumble in a totally dry state. Desiccation tolerance was associated with those first steps of land colonisation by plants, adding an evolutionary note whenever I take a hand lens to tuft of moss and watch it rehydrate. I never tire of seeing twisted dried leaves unfurl, sighing open with just a spray of water.

Like other bryophytes, mosses are often overlooked. But once you notice them, they draw you in, then, with newly found moss-attuned vision, you realise that moss is a member of many ecosystems, whether woodland, urban or even beachside. Now that I study moss, I have an eye out for it everywhere I go. Is that moss I see growing in this playground on plastic turf? Yes - moss reminds us that wild processes occur all around us, whether we take notice or not. On the cusp of micro and macro, it has the ability to alter your perception of the world.

After the fire. Australia

When I get asked what I'm doing when I'm out and about in the suburbs, it's nice to be able to share some basic facts about moss. Usually, people think of it as only found in moist habitats, so they are surprised to learn that desert mosses inhabit our city pavements. But as members of the IAB will be well aware, moss is both ubiquitous and picky. Ubiquitous in that there are thousands of species (10 000 at least according to the Tree of Life Web Project) and these grow in an astonishing variety of places: among other biocrust organisms (such as lichen, fungi, bacteria) in deserts; on trees in rainforests and on ground that is newly exposed, as glaciers retreat in Antarctica. But picky too, in that substrate – the kind of rock, for instance – also largely dictates whether a particular species can grow there. For example, I'm looking at moss on an urban gradient on three substrates - pavement cracks, asphalt dimples (such as car park edges) and soil in grassy green spaces. The species vary according to substrate (albeit with a few that have wide ranges and can tolerate all three). But whether it's the CBD or Antarctica, where moss grows depends on a combination of factors including microclimate (the humidity, temperature and so on, at the scale it matters to a moss) and microtopography.

Science is my second career (my first career focus was publishing) and one of the reasons I turned back to biology was to go into the field and experience places I otherwise would not have the opportunity to visit. Moss, albeit small, has not disappointed on this front. Travelling for conferences has allowed me to witness the micro 'mountains' of biocrusts in Utah, urban moss and night markets in Shenzhen, and the wonderful IAB/iMOSS conference in Madrid's Royal Botanic Garden last year (hot on the heels of the SEB in Seville). Visiting the Prado was a highlight. Little moss there, it's true, but Goya's May 3rd moved me to tears. The field trip to the Parque Regional de la Cuenca Alta del Manzanares provided a special opportunity to see numerous dry adapted moss species in the wild. Early last year, in February 2020, moss took me camping in Antarctica, and I delivered the moss back to Australia in the form of samples from sites on King George Island glacier retreat. The samples now sit in a freezer in Wollongong, awaiting analysis for C13, which will show what conditions were like as it grew, and possibly C14 for dating purposes.

Currently, however, my research is taking me out into the suburbs of Wollongong, a coastal city in NSW, where watching closely for moss also makes me appreciate neighbourhoods I wouldn't usually visit, whether it's the expansive beaches of Windang in the south, or the bourek shops in the migrant suburb of Cringila.

So next time I'm asked, ‘why do you study moss?’ I now have a ready answer: for its rich research potential; because it's thought-provoking philosophically; and because it leads me to places near and far.