Plants and plant communities of Strangford Lough islands

I presented this poster at the October 2022 BSBI Conference at the Natural History Museum in London. Read about my experience at the conference here.

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Conference Flash Talk

October 2022 I gave a short flash talk on my poster at the BSBI conference.

Sea Mayweed Tripleurospermum on Great Minnis's

An Eyebright species Euphrasia nemorosa on Roe, note also a white form of Odontites vernus (Red Bartsia). This form was common on several of the islands.

MG1e grassland with abundant Knapweed Centaurea on Roe.

H7b heath with Bell Heather Erica cinerea on Darragh.

A Six-Spot Burnet moth Zygaena filipendulae nectaring on Sneezewort Achillea ptarmica on Darragh.

A Hummingbird Hawkmoth Macroglossum larva on Lady's Bedstraw Galium verum on Darragh.


Strangford Lough is a large sea lough in Vice-county H38 (Down), in the North-East of Ireland. Formed by glaciation, it has many iconic drumlin islands.

These are of conservation importance, especially for their grassland and saltmarsh, and for birds and seals. However, the flora is poorly studied, if at all.

Agricultural improvement on the mainland has led to these islands becoming refugia for many grassland species (such as Linum catharticum, Euphrasia nemorosa).

I recorded the plants and NVC plant communities of eleven islands around the townland of Ballymorran, which can be grouped by what grazes them:

None Craigaveagh, Parton, Shamrock
Geese Inisharoan
Sheep Green
Geese, Sheep Inishanier, Roe
Geese, Cattle Drummond, the Minnis's
Sheep, Cattle Darragh



A quadrat on Roe.


Species richness and area


Me kayaking in front of Darragh.

Area and species richness

Species richness correlates with the area of the island, with a linear relationship when the values are log-transformed (fig. 1; R 2 = 0.8356 , F 1,9 = 45.74 , p < 0.0001 ). Residual variance is undoubtedly at least partially caused by differences in grazing, although the sample size is too small to test these effects. It would be particularly interesting to see whether Darragh is an outlier for its size, and whether sheep-grazed islands are significantly less diverse.

Fig. 1: log-log graph of island species richness and area.

Plant communities on the islands

Hogweed Heracleum dominated sward on Drummond.

Redshank Persicaria maculosa and Marsh Yellow-Cress Rorippa palustris in the large pond on Drummond.

Darragh island management

Fig. 2: plant communities of Darragh Island. Scale bar = 100m.

Conservation on the islands

Fig. 3: plant communities of Roe Island. Scale bar = 100m.


Thanks to all the landowners: Kathryn McBride, John Dynes, Leanna McBride, and Alison Oliver. Thanks to the county recorder Graham Day for help with species ID. Thanks to Wayne Liang for help with statistics. Thanks to my parents, Judith and Keith Dalzell, for help with transport and kayaking!

Huge thanks to the BSBI who generously provided a plant study grant to make this research possible.


  1. Lister, J.A. & Alexander, K.N.A. 1999. Strangford Lough, Co Down (excluding wildfowl, waders & marine)1998 Survey Incorporating 1985 Survey. Internal report (biological survey). National Trust.
  2. National Trust, 2020. 200-year-old tradition of island farming on Strangford Lough [online]. [Accessed 27 October 2022]. Available at: