The human influences shaping peatland vegetation communities

This blog by Alice Noble discusses peatland protection policy and follows her recent article in Journal of Applied EcologyPrescribed burning, atmospheric pollution and grazing effects on peatland vegetation composition.

As sloping expanses of shrubs, sedges and moss where the only sounds are wind, rain and birds, with no people in sight, blanket peatlands can feel like wild and remote places. In the UK, these upland landscapes make up the largest remaining semi-natural habitat, and on most days everything is quiet. Contrary to appearances though, humans have shaped the ecology of these areas and our actions continue to impact what grows there.

Blanket peatland ecosystem function relies on key peat-forming plants, with Sphagnum moss playing a vital role in carbon storage and hydrological regulation. However, there are concerns that anthropogenic impacts including routine pressures like grazing and atmospheric pollution as well as periodic disturbance from prescribed burning could be harmful to Sphagnum and other peat forming plants, perhaps even encouraging less desirable species at their expense. For our new study published in Journal of Applied Ecology we used both regional and national scale datasets to explore associations between plant communities and burning, atmospheric pollution and grazing on blanket peatlands.

Human impacts

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Prescribed burning on blanket bog (Photo: Alice Noble)

Large areas of the UK uplands, including some blanket peatlands, are managed for shooting of the game bird red grouse. For around 150 years, gamekeepers have been rotationally burning small strips of vegetation annually, creating a patchwork landscape of different heather (Calluna vulgaris) ages which provide both cover and food for grouse, increasing productivity. Grouse shooting remains a popular sport, and the amount of burning taking place on some blanket peatlands has increased in recent decades. However, concerns about the impacts of burning on peatland soils and vegetation have led to heated debate about the sustainability of the practice. Our results show that nationally, recently burned peatlands have lower Sphagnum cover. On sites where increasing or maintaining Sphagnum is a priority, burning may therefore be inadvisable. Furthermore, the regional dataset showed that the non-native moss Campylopus introflexus was much more abundant on recently burned sites, suggesting a risk of this species taking over from native mosses where burning is frequent.

Atmospheric pollution has historically had a big impact on peatlands near industrial centres, in some cases wiping out local populations of pollution sensitive Sphagnum. Our results confirmed that areas with higher pollution levels still have less Sphagnum cover, and uncovered an interaction between prescribed burning and nitrogen deposition. The negative effect of nitrogen deposition on Sphagnum, and the positive effect on C.introflexus were stronger on recently burned sites. This indicates that burning may have a greater impact in areas with higher atmospheric pollution. Although grazing on blanket peatland is often sparse, livestock presence was also associated with less cover of both Sphagnum and heather.

Protecting peatlands

The results of the study show that anthropogenic influences are associated with differences in peatland vegetation, and suggest that Sphagnum cover is vulnerable to decline under current management practices and environmental conditions. The debate surrounding prescribed burning is complex and a widely accepted solution may not be easily reached. However, given our findings, we suggest that observing good practice codes, particularly guidance that there should be a strong presumption against burning on areas of deep peat, is appropriate. Further work developing our understanding of the processes via which anthropogenic impacts affect peatlands is likely to be valuable moving forwards in the management of these important landscapes.

The full Open Access article, Prescribed burning, atmospheric pollution and grazing effects on peatland vegetation composition is available in Journal of Applied Ecology.

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