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Forests play a key role in climate change mitigation, adaptation and delivery of a range of ecosystem services. There is increasing evidence for impacts of climate and other drivers on plant community change, and fragmented habitats are predicted to be much less resilient to negative impacts on biodiversity and other services. Within Europe, Scotland's native forests are highly fragmented and now cover 4% of the land after many centuries of degradation and loss, but little is known about how their species composition has changed. We recorded long-term vegetation change (from resurvey data) and examined the relationships with climate, pollutant deposition and grazing as key drivers of change, focusing on four forest types: pine, ash, acid- and base-rich oak-birch. All four forest types showed dynamic compositional change during 30–50 years between surveys, with increased species richness and decreased diversity. There was no evidence for homogenisation - the opposite was the case for all except pine (no change). Analyses indicate significant and varied climate, pollution and grazing impacts; NHy deposition showed the most frequent association with species compositional changes. Notable species changes include increases in pteridophytes and declines in forb cover, and a doubling in frequency and cover of Fagus sylvatica between surveys. Our findings suggest a possible extinction debt, with many more species declining than increasing between surveys. This trajectory of change and our other findings indicate a pressing need for mitigation management to reduce the risks of future species losses, with forest expansion planning explicitly considering spatial location in relation to existing native forest and those plant species identified as most at risk.

Globally, peatlands provide an important sink of carbon in their near natural state but potentially act as a source of gaseous and dissolved carbon emission if not in good condition. There is a pressing need to remotely identify peatland sites requiring improvement and to monitor progress following restoration. A medium resolution model was developed based on a training dataset of peatland habitat condition and environmental covariates, such as morphological features, against information derived from the Moderate Resolution Imaging Spectroradiometer (MODIS), covering Scotland (UK). The initial, unrestricted, model provided the probability of a site being in favourable condition. Receiver operator characteristics (ROC) curves for restricted training data, limited to those located on a peat soil map, resulted in an accuracy of 0.915. The kappa statistic was 0.8151, suggesting good model fit. The derived map of predicted peatland condition at the suggested 0.56 threshold was corroborated by data from other sources, including known restoration sites, areas under known non-peatland land cover and previous vegetation survey data mapped onto inferred condition categories. The resulting locations of the areas of peatland modelled to be in favourable ecological condition were largely confined to the North and West of the country, which not only coincides with prior land use intensity but with published predictions of future retraction of the bioclimatic space for peatlands. The model is limited by a lack of spatially appropriate ground observations, and a lack of verification of peat depth at training site locations, hence future efforts to remotely assess peatland condition will require more appropriate ground-based monitoring. If appropriate ground-based observations could be collected, using remote sensing could be considered a cost-efficient means to provide data on changes in peatland habitat condition.

Empirical critical loads are widely used to quantify and manage the ecological impacts of reactive nitrogen (N) deposition. Critical load values aim to identify a level of N deposition below which significant harmful effects do not occur according to present knowledge. Critical loads have been primarily based on experiments, but these are few in number and have well-known limitations, so there is a strong imperative to test and validate values with other forms of evidence. We assembled data on the spatial variability in vegetation communities in the United Kingdom and used Threshold Indicator Taxa Analyses (TITAN) to investigate linkages between species changes and modelled current and cumulative N deposition. Our analyses focused on five datasets: acid grasslands, alpine habitats, coastal fixed dunes, dune slacks and wet grasslands. In four of these habitats there was evidence for a significant decline in the cover of at least one species (a ‘species-loss change-point’) occurring below the critical load, and often at very low levels of N deposition. In all of the habitats there was evidence for clustering of many individual species-loss change-points, implying a community change-point analogous to an ecological threshold. Three of these community change-points occurred below the critical load and the remaining two overlapped with the critical load range. Studies using similar approaches are now increasingly common, with similar results. Across 19 similar analyses there has been evidence for plant species loss change-points below the critical load in 18 analyses, and community-level species loss change-points below the critical load in 13 analyses. None of these analyses has shown community change-points above the critical load. Field data increasingly suggest that many European critical loads are too high to confidently prevent loss of sensitive species.

Nitrogen (N) deposition poses a severe risk to global terrestrial ecosystems, and managing this threat is an important focus for air pollution science and policy. To understand and manage the impacts of N deposition, we need metrics which accurately reflect N deposition pressure on the environment, and are responsive to changes in both N deposition and its impacts over time. In the UK, the metric typically used is a measure of total N deposition over 1–3 years, despite evidence that N accumulates in many ecosystems and impacts from low-level exposure can take considerable time to develop. Improvements in N deposition modelling now allow the development of metrics which incorporate the long-term history of pollution, as well as current exposure. Here we test the potential of alternative N deposition metrics to explain vegetation compositional variability in British semi-natural habitats. We assembled 36 individual datasets representing 48,332 occurrence records in 5479 quadrats from 1683 sites, and used redundancy analyses to test the explanatory power of 33 alternative N metrics based on national pollutant deposition models. We find convincing evidence for N deposition impacts across datasets and habitats, even when accounting for other large-scale drivers of vegetation change. Metrics that incorporate long-term N deposition trajectories consistently explain greater compositional variance than 1–3 year N deposition. There is considerable variability in results across habitats and between similar metrics, but overall we propose that a thirty-year moving window of cumulative deposition is optimal to represent impacts on plant communities for application in science, policy and management. © 2019 Measures of nitrogen deposition which incorporate long-term pollution history explain more spatial variance in plant communities than those which do not. © 2019

Question Dwarf shrub moorland dominated by ericaceous plants is a distinctive, internationally important feature of northwest Europe, with its stronghold in Scotland. There have been major declines in its condition and extent. How has moorland composition changed within Scotland over the past ca. 35 yr and what is the role of climate change, pollution and grazing in driving these changes? Location Five hundred and forty locations across Scotland, UK. Methods We used a long-term resurvey approach to assess change across Scottish moorlands. We relocated plots sampled ca. 35 yr previously in alpine heath, dry heath, wet heath and bog, and recorded vegetation species composition. We assessed change in species group richness and cover and mean Ellenberg values between surveys, using paired t-tests. We used CCA with variation partitioning and regression analysis to analyse the vegetation data with spatial data sets on climate, pollution and grazing, to assess the role of each driver in driving vegetation changes. Results Significant diversity and compositional changes between surveys were found for all habitat types, particularly alpine heath. Significant associations were found with climate (many variables), pollution (N and S) and herbivore number (primarily deer). Species richness generally increased, but several specialist species declined in cover, especially those associated with higher altitude habitats (e.g. Arctostaphylos uva-ursi, Salix herbacea and alpine lichens). Many of the most successful species are ubiquitous, e.g. the widespread grazing- and pollution-tolerant graminoids Anthoxanthum odoratum, Juncus squarrosus, Festuca rubra and Nardus stricta and the generalist mosses Rhytidiadelphus squarrosus and Hylocomium splendens. Conclusions Diversity and composition of moorlands in Scotland have changed significantly over the ca. 35-yr period studied; the drivers of these changes are complex, with climate, pollution and grazing playing variable roles across habitats. The reduction in specialist species, homogenization of alpine heaths and declines in forb and lichen cover all represent negative changes in the biodiversity value of Scottish moorlands.

Whilst a number of studies have examined the effects of biodiversity conservation on the delivery of ecosystems, they have been often limited by the scope of the ecosystem services (ES) assessed and often suffer from confounding spatial issues. This paper examines the impacts of nature conservation (designation) on the delivery of a full suite of ES across nine case-studies in the UK, using expert opinion. The case-studies covered a range of habitats and explore the delivery of ES from a ‘protected site’ and a comparable ‘non-protected’ site. By conducting pair-wise comparisons between comparable sites our study is one of the first to attempt to mitigate confounding cause and effect factors in relation to spatial context in correlative studies. Protected sites delivered higher levels of ecosystem services than nonprotected sites, with the main differences being in the cultural and regulating ecosystem services. Against expectations, there was no consistent negative impact of protection on provisioning services across the case-studies. Whilst the analysis demonstrated general patterns and differences in ecosystem delivery between protected and non-protected sites, the individual responses in each case-study highlights the importance of the social, biophysical, economic and temporal context of individual protected areas and the associated management.

Low-frequency mowing has been proposed to be an effective strategy for the restoration and management of boreal fens after abandonment of traditional haymaking. This study investigates how mowing affects long-term vegetation change in both oceanic and continental boreal rich-fen vegetation. This will allow evaluation of the effectiveness of mowing as a management and restoration tool in this ecosystem in the face of climate change. At two nature reserves in Central Norway (Tågdalen, 63° 03’ N, 9° 05 E, oceanic climate and Sølendet, 62° 40’ N, 11° 50’ E, continental climate), we used permanent plot data from the two sites to compare plant species composition from the late 1960s to the early 1980s with that recorded in 2012–2015 in abandoned and mown fens. Changes in species composition and frequency were analysed by multivariate and univariate methods in relation to environmental variables and modelled climate and groundwater data. Mowing resulted in a decline in shrub and Molinia caerulea cover at the continental and oceanic sites respectively, and the total cover of specialist fen species had increased to a significantly greater extent in the mown plots than the unmown at the continental site. However, mowing did not have an effect on the cover of specialist bryophyte species, and some specialist species declined regardless of mowing treatment. Temperature sums had increased at both sites, but precipitation had not changed significantly. Mowing was shown to be the most important determinant of plant community composition at both sites, with local environmental conditions being of secondary importance. In conclusion, the abandonment of traditional management practices results in the loss of characteristic fen species. In order to encourage the restoration of typical rich-fen vegetation, particularly in oceanic areas, additional management measures, such as more intensive mowing, may be required. Copyright: © 2019 Ross et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Sheep grazing is an important part of agriculture in the North Atlantic region, defined here as the Faroe Islands, Greenland, Iceland, Norway and Scotland. This process has played a key role in shaping the landscape and biodiversity of the region, sometimes with major environmental consequences, and has also been instrumental in the development of its rural economy and culture. In this review, we present results of the first interdisciplinary study taking a long-term perspective on sheep management, resource economy and the ecological impacts of sheep grazing, showing that sustainability boundaries are most likely to be exceeded in fragile environments where financial support is linked to the number of sheep produced. The sustainability of sheep grazing can be enhanced by a management regime that promotes grazing densities appropriate to the site and supported by area-based subsidy systems, thus minimizing environmental degradation, encouraging biodiversity and preserving the integrity of ecosystem processes.