brownfield sites in Scotland Richard Milne

RICHARD MILNE

Brownfield sites are increasingly recognised as being important for biodiversity, with much of the countryside being given over to monocultures of crops or conifers, and grazed fields bereft of flowers. Post-industrial ‘waste ground’ can host a wide diversity of plants, generally a mixture of native and naturalised taxa, often supplemented with a few unusual garden escapes or outcasts. The plants and animals that make a life on such sites are part of an ongoing story of how wild species have had to adapt to the presence of human beings. Species that do well here tend to be those favouring disturbed and/or poor soils. Hence it was quite extraordinary to come across a large colony of Britain’s only eukaryotic holoparasite on fungi, Hypopitys monotropa (Yellow Bird’s-nest), on a brownfield site in Edinburgh, and then to learn that this is not an isolated incident.

Hypopitys is very rare in Scotland. It has not been recorded north of the central belt this century, though it may still lurk unseen in Tentsmuir Forest

Above: Hypopitys monotropa (Yellow Bird’s-nest) growing inside a discarded car tyre at Kirkintilloch, July 2020 (v.c. 86). Michael Philip

(Fife) and near Killiecrankie, both of which have post-1970 records. Since 2010, however, it has been recorded from six other tetrads in the central belt, the northernmost just south of the Kincardine Bridge. The most striking record is from a post-industrial site by Kirkintilloch (v.c.86, Stirlingshire), communicated to me by Vice-county Recorder Michael Philip after I asked him about the habitats of the species in Lanarkshire. A local artist, Tom Wilson, had been exploring a post-industrial brownfield site near Kirkintilloch. His description of the place closely matches my own site at Moncktonhall: ‘rubble, building debris, abandoned car parts and tons of fly-tipped rubbish’ (Philip, 2020). Indeed, among the hundreds of flowering spikes of H. monotropa that he found, one large group was growing happily through the

middle of a discarded, partly buried car tyre (see main photograph on previous page and cover image). In total, Tom counted a remarkable 340 flowering spikes (Philip, 2020), making it surely one of the largest populations in Britain, and certainly in Scotland. Sadly, this site has now been developed, although some of the Hypopitys plants were transplanted to a safer spot. Before last year I’d have assumed that such transplants were unlikely to succeed, based on the peculiar needs of the species, but its ability to reach and thrive in brownfield sites suggests that these transplants might have a real chance of success. Time will tell.

Michael also told me of another site, a community woodland near Cambuslang, Glasgow, where the species occurs in far smaller numbers. This site is scrub woodland with some introduced pine saplings that could have brought the species with them, hence certainly not an ancient woodland.

The Midlothian site, at Millerhill Bing, Moncktonhall, on the outskirts of Edinburgh, is part of a botanically remarkable brownfield area, comprising flat post-industrial waste ground and a raised coal bing, formerly connected but now separated by the newly built borders railway line. There is also now a huge waste-processing plant, built at the same time as the railway, around 2013. These developments destroyed two of the most interesting plants on the site – a sizeable population of Galium parisiense (Wall Bedstraw), and the only individual

Millerhill Bing, Moncktonhall, July 2021. Richard Milne of Anacamptis pyramidalis (Pyramidal Orchid) ever recorded from Midlothian. Populations of locally rare natives Gentianella amarella (Autumn Gentian) and Clinopodium vulgare (Wild Basil) were also lost. However, the raised bing was largely unaffected, and its dark rocky surface supports large numbers of Linum catharticum (Fairy Flax), Echium vulgare (Viper’sbugloss), Teucrium scorodonia (Wood Sage), Logfia minima (Small Cudweed), Filago germanica (Common Cudweed), Centaurium erythraea (Common Centaury) and Hypericum perforatum Perforate St John’s-wort. Buddleia davidii (Butterfly-bush) is the most common shrub, and locals report that it was actually planted there after the mining was discontinued, to help the area go back to nature. Other well established aliens include Verbascum virgatum(Twiggy Mullein), Hypericum olympicum (Olympic St John’s-wort), Clematis tangutica (Orange-peel Clematis), and Potentilla recta (Sulphur Cinquefoil). Several Lychnis viscaria (Sticky Catchfly) plants also turned up here in 2019, but these have since rapidly dwindled and might have been deliberately introduced.

Unable to run a residential field course due to Covid restrictions, I took two sets of botany students to explore this site, and conduct mini-projects. This added a few more species to the site: Anthyllis vulneraria subsp. vulneraria var. langei (Kidney Vetch) turned up in large numbers, along with a single plant of Urtica membranacea (Mediterranean Nettle) on dumped soil nearby. On the waste ground site we came across a large patch of Lathyrus nissolia (Grass Vetchling) near a segregating hybrid zone of Linaria purpurea (Purple Toadflax) and L. repens (Pale Toadflax), which like the Urtica was a first for Midlothian. A group of MSc students used the key in Stace (2019) to confirm my ID of Verbascum phlomoides (Orange Mullein), yet another new v.c. record, and with a striking white form among the yellow ones.

The discovery of H. monotropa came about in delightfully haphazard fashion. Accompanying me on one these excursions came Vlad Krivtsov, a talented all-round naturalist, and it was he who first saw the Hypopitys when he returned to the site alone after our second field trip, to try and refind a Pyrola minor (Common Wintergreen) population I’d shown

him earlier. He noticed the yellow stems just starting to emerge, but was not familiar with the species and hence did not know what they were. So it wasn’t until I accompanied him and his MSc students to the site later on that it was identified, with a jolt of shock and joy. It was a thriving population, over 100 stems in all, more than I’d ever seen elsewhere, yet still many fewer than at Kirkintilloch. They grow on a thick gravelly substrate topped with moss and leaf litter, among young birch and willow trees. Pyrola minor occurs in large quantities nearby in the same woods, though curiously the patches of these do not seem to overlap. There are some flowering spikes of H. monotropa that rise from right beside the slowly eroding concrete frames of access shafts to underground tunnels, emphasising the mix here of the wild and artificial (see photo, next page). Based on my photos, Fred Rumsey confirmed the plants to be the commoner subspecies hypophegea.

Stace (2019), in common with other UK plant guides, states that H. monotropa mostly occurs in beech or pine woods (or dunes), so its presence among willow and birch is in itself unusual, whereas at Cambuslang the main tree seems to be Hawthorn (Crataegus monogyna); at Kirkintilloch it is Goat Willow (Salix caprea). Of course, from the plant’s perspective, it is not the tree but the presence of a suitable fungus that determines where it can grow. Fred Rumsey reports one site at Hawley in secondary woodland and a few cases of it turning up in disused quarries. This pattern of occurrence recalls certain orchids like Dactylorhiza fuchsia (Common Spotted-orchid), D.purpurella (Northern Marsh-orchid) (both present at Moncktonhall) and Ophrys apifera (Bee Orchid) (which coincidentally appeared on a redeveloped landfill site in Lanarkshire at around the same time, new for the vice-county). It may be no coincidence that orchids also parasitise fungi, at least when young, and the effect of human disturbance on fungal populations might be key to all these occurrences.

The question of how H. monotropa arrived at all these sites is clearly of interest – Midlothian is a well botanised vice-county, and it seems unlikely that long-lived populations of this striking plant could have remained undetected in those fragments of

Hypopitys monotropa (Yellow Bird’s-nest) at Millerhill Bing (Midlothian, v.c. 83), growing in leaf litter, 26 August 2021. Richard Milne

ancient woodland that remain, especially given the tendency of its fruiting stems to remain as jet black sentinels marking the spot all the way through to the next flowering season. That said, a team of ecologists apparently missed it completely when surveying the site in autumn 2021. Still, on balance it is likely a recent arrival here, and perhaps also in some of its other central belt sites.

Every post-2000 Scottish locality is at least 10km from its nearest neighbour, and the closest to the Moncktonhall population is 35km away (near Stoneyburn). The seeds have no special adaptation for dispersal, and the only natural mechanism that is at all plausible might be the feet of birds, but overall, natural dispersal seems very unlikely. The activity

Hypopitys monotropa growing beside a concrete slab at Millerhill Bing, 9 July 2022. Richard Milne associated with railway and building construction around 2013 might have brought in the seed, but if so the species has expanded remarkably quickly. Alternatively, seed could have been inadvertently carried to the area by human activity at an earlier date. If the buddleias on the bing were deliberately planted, might some of the trees here have been also, in a bid to propel this stricken site back towards nature? It might explain why there is such an abrupt edge to the birch woodland here. If so, perhaps the Hypopitys plants came in with transplanted young trees, as is suggested for the Cambuslang site. Even so, this begs another question: if the plant is so rare in Scotland, how did it get among the source trees? Could the species be a lot commoner than we think, but like certain orchids lurk unseen in the soil underground, not flowering until conditions are right? Much remains to be understood here.

Without doubt, this large population of a rare native species brings an unusual but compelling conservation case for this site. The population narrowly escaped disaster at the start of 2022, after some of the young woodland around them was felled as part of plan to build a pipeline. Miraculously, the epicentre of the population was left standing, and I was able to speak to the workers on site and show them the plant. They were very responsive, and assured me it would be safe for the foreseeable future. Some might argue that the biodiversity of a particular brownfield site is expendable, because any species that can establish on such disturbed sites should therefore be able to establish easily enough on other similar sites in the future. Yet older brownfield sites can be home to rare species with specific requirements, as these Scottish Hypopitys populations have shown. We may learn from the Kirkintilloch site whether transplantation for conservation is a viable option for this species, and it is to be hoped that these remarkable populations will be conserved. Among other things, it brings with it a welcome ray of hope that even rare and specialist species may sometimes find ways to make new homes in landscapes that have been dramatically altered by human activity.

Thanks are due to Michael Philip and Fred Rumsey for discussions and information about the plants, and especially to Michael for filling me in on the remarkable Lanarkshire site, correcting a few errors in an earlier draft and supplying the photograph.

Philip, M. 2020. Lanarkshire Botany Newsletter, 2020 Summary,

November 2020. Stace, C.A. 2019. New Flora of the British Isles (4th edn). C & M

Floristics, Middlewood Green, Suffolk.

Institute of Molecular Plant Sciences, School of Biology, University of Edinburgh, Mayfield Road, Edinburgh, EH9 3JH