Oceanic wet grasslands in the Scottish coastal lowlands – publication now available

Our work on the Oceanic wet grasslands of Scotland, assessing the vegetation of the species-rich wet grasslands in machair and other coastal systems of Scotland, has been published in 'British and Irish Botany'. It is available to read in full here: 

https://britishandirishbotany.org/index.php/bib/article/view/170 

The lack of clear community definitions for the oceanic wet grasslands of Scotland has resulted in them being overlooked in some conservation schemes, which have tended to focus primarily on the vegetation of the cultivated machair and associated sand dunes. This study has now brought together data from multiple historic surveys, alongside data collected by field surveyors between 2018 and 2021, to recognise five distinct vegetation communities that could be further segregated into ten units equivalent to subcommunities of the British National Vegetation Classification (NVC; Rodwell, 1991 et seq). 

These communities are shown as being distinctive from other vegetation communities defined across Europe (albeit with some cross over to a small number of Irish communities) and can therefore be seen as unique to the western and northern seaboard of Scotland. They have been called Oceanic Wet Grasslands. The new communities have been defined as outlined in table 1. They are located across a hydrological gradient, as shown in Fig. 1. 

Table 1. Summary of names for the proposed Scottish Oceanic wet grassland communities and subcommunities with proposed NVC codes

Figure 1. An illustrative cross-section of a machair system, which indicates the relative positions of the new vegetation communities with reference to their soil and hydrological environment. Dipwells are installed to monitor water-table depths within each vegetation community. Vicky Bowskill

There are clear relationships between the plant communities, hydrology and soil fertility.

• MG14 tends to be found on the more fertile soils of high moisture

• MG20 Carex nigra-Potentilla erecta-Rhytidiadelphus squarrosus grassland occupies less fertile but slightly wetter substrates.

• MG19 a and b (Caltha palustris-Carex nigra) occupy the wettest and least fertile soils 

• MG18 is in the middle of the hydrological gradient and also has intermediate fertility between the less fertile MG19 and MG20 and the more fertile MG17 

• MG17 a and b (Agrostis stolonifera-Bellis perennis) are found on the driest and most fertile soils.

The botanical diversity of all the plant communities is high, and their rarity means they should be prioritised for conservation effort. MG18 and MG19 in particular display exceptionally high botanical diversity with a maximum of 49 species recorded in one square metre in some of the surveys. MG17 and MG20 are still high in diversity, but lower, with a maximum number of species per quadrat recorded at 35 sp/m2. MG14 is generally of lower diversity, sitting at the higher fertility and wetter end of the gradient, and averaging 14 species/m2, with a maximum of 23 species per m2. 

The value of the plant communities is primarily in their diversity. However, they also provide habitat for a number of threatened species that are listed as Vulnerable or Endangered on the new vascular plant Red List for Great Britain (Stroh et al., 2025), such as Baldellia ranunculoides, Botrychium lunaria, Dactylorhiza viridis, Helosciadium inundatum, Oenanthe fistulosa, Oenanthe lachenalii, Parnassia palustris, Platanthera bifolia, Sagina saginoides, Succisa pratensis, Triglochin palustris, Trollius europaeus and Vicia lathyroides.

These findings are being incorporated into a wider review of additional NVC grassland types by the statutory conservation agencies, who are also assessing whether there is a need to explicitly refer to these and other new grassland communities in the Lowland Grassland SSSI Selection Guidelines.

References

Rodwell, J.S. ed. 1991. et seq. British Plant Communities.  Cambridge, CUP.

Stroh, P.A., Pescott, O.L., Bateman, R.M.. et al. (2025) A new vascular plant Red List for Great Britain. British & Irish Botany 7(3), 148-216