Holocene landscape evolution of the Mourne Mountains, Northern Ireland

Abstract

The Mourne Mountains are an upland area in County Down, Northern Ireland. Today, the Mournes host an open landscape characterised by degenerating blanket peat and heath communities. Archaeological and historical records attest to human presence here over preceding millennia. The environment, however, is under immense pressure due to recent land-use activities; conservation is critical if the natural and cultural heritage of the Mournes is to be preserved. This thesis aims to use a  palaeoenvironmental approach to disentangle the Holocene landscape of the Mourne Mountains in order to inform conservation and to enhance understanding of cultural heritage in the region.

This study shows that blanket peats began forming from at least ~8700 BP and by the mid-7th millennium BP blanket bog was widespread across the uplands. Radiocarbon dating is shown to return erroneous ages of peat initiation; cryptotephra analysis is demonstrated as a reliable means to independently date blanket peat deposits. Samples of modern pollen rain from across the Mournes emphasise that uplands are susceptible to long-distance pollen transport; this knowledge guides interpretation of landscape evolution from deep-peat sequences. Pollen analyses show that contrary to common thought, the high hills of the Mournes were not wooded during the mid-Holocene. Pinus woodland was formerly local to lower mountain slopes (less than 350 m above sea level) until its decline around ~6750 BP. The high hills of the Mournes have hosted heath over the last ~9000 years and this replaced local Pinus woodland on the lower slopes after its decline. Analysis of pollen and non-pollen palynomorphs from samples adjacent to former transhumant sites show occupation from the mid- to late 12th century CE until ~1800 CE; activities included cereal-growing and grazing. Cereals were also grown in cultivation ridges that lie relict from year-round settlement in the mountain foothills during the late 18th to early 20th century CE.

This thesis demonstrates that the Mournes have hosted a distinct landscape relative to other Irish uplands during the Holocene. Humans were present in prehistoric times, but activity and impact on the environment was limited – possibly due to the early origin of blanket bog. Results hint that significant human impact may have begun during the Early Medieval period, but intensified activity since ~1850 CE, which is analogous to other Irish uplands, has been most impactful to the landscape. Conservation in the Mournes is, therefore, challenging as a balance must be struck between preserving the blanket bog and heath communities that are natural to the uplands and ingrained in cultural traditions.

Thesis is embargoed until 31st July 2028.

Date of Award	Jul 2025
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	Northern Ireland Department for the Economy & Geological Survey of Northern Ireland
Supervisor	Gill Plunkett (Supervisor) & Maarten Blaauw (Supervisor)