Species composition of coastal dune vegetation in Scotland has proved resistant to climate change over a third of a century

Abstract

Climate change is expected to have an impact on plant communities as increased temperatures are expected to drive individual species' distributions polewards. The results of a revisitation study after c. 34 years of 89 coastal sites in Scotland, UK, were examined to assess the degree of shifts in species composition that could be accounted for by climate change. There was little evidence for either species retreat northwards or for plots to become more dominated by species with a more southern distribution. At a few sites where significant change occurred, the changes were accounted for by the invasion, or in one instance the removal, of woody species. Also, the vegetation types that showed the most sensitivity to change were all early successional types and changes were primarily the result of succession rather than climate-driven changes. Dune vegetation appears resistant to climate change impacts on the vegetation, either as the vegetation is inherently resistant to change, management prevents increased dominance of more southerly species or because of dispersal limitation to geographically isolated sites.

Drivers of species richness and compositional change in Scottish coastal vegetation

“…The second resurvey was carried out between 2009 and 2011 (Pakeman et al. ); with one site surveyed in 2013 due to issues with safe access (2010 is used as the shorthand for this survey). In total 89 out of the original 94 sites and 3862 out of 4079 quadrats were re‐visited, with the fate of each quadrat between surveys recorded.…”

Functional similarity analysis highlights ecosystem impacts and restoration needs

“…The identification of climate as the main environmental driver of similarity (Table ) suggests that stability was higher in the high rainfall, low temperature area. However, as these habitats have appeared resilient in the face of climate change (Pakeman et al., ), it is likely that the climate drivers are a proxy for land‐use changes not adequately described with the available data; the northwest to southeast division for the climate drivers reflects the maintenance of traditional grazing management in northwestern areas and a lack of grazing in southeastern areas, where agriculture no longer has a significant livestock component (Pakeman et al., ). There was a high degree of similarity in the drivers correlated to Retention and Gain.…”

“…Functional β‐diversity was assessed using species composition data from two vegetation surveys of Scottish dune and machair sites (Pakeman et al., ; Shaw, Hewett, & Pizzey, ). Survey one carried out from 1975 to 1977 and survey two from 2009 to 2011 (one site resurveyed in 2013 due to safe access restrictions).…”

“…Yearly values of mean temperature (Temp, °C) and total precipitation (Rain, mm) were calculated from the monthly data in the UKCP09 5 ×5 km gridded database (Perry & Hollis, ) for 1976 to 2010. Averages of these annual values between the two surveys were used as predictors as changes in climate have been relatively uniform across the area surveyed and climate change measures had not performed well in analysis of other aspects of these data (Pakeman et al., , ). On the same grid, modelled cumulative total nitrogen (ΣN) and sulphur (ΣSOx) deposition (both shown as important drivers of species change and loss; Pakeman et al., , ) for the period between the two surveys (1976 to 2010) were obtained from the CBED model (Smith, Fowler, Sutton, Flechard, & Coyle, ) using historical scaling factors (Fowler et al., ) on a base year of 2005.…”

“…To test the approach a data set collected from a resurvey of coastal plant communities in Scotland, UK (Pakeman et al., ), was analysed using this framework to address the following questions: (i) which habitats have shown the highest level of functional β‐diversity over time; (ii) are levels of functional β‐diversity correlated to known changes in environmental drivers; (iii) can comparison with species β‐diversity estimates reveal further information relating to environmental change; and (iv) does this approach highlight sites of particular conservation concern – sites where functional changes might alter vegetation‐dependent ecosystem service delivery or sites where restoration is required?…”