Marine biodiversity and climate change: twenty-five years of changes in abundance and distribution of rocky intertidal species in the UKBroad-scale Spatial Patterns

Michael Burrows¹, Heather Sugden², Nova Mieszkowska^3,4, Steve Hawkins^4,5

¹Scottish Association for Marine Science, UK - ²Newcastle University, UK - ³University of Liverpool, UK - ⁴The Marine Biological Association, UK - ⁵University of Southampton, UK

Designed to detect the impacts of climate change and building on a long history of similar studies, a 25-year programme of systematic surveys of rocky intertidal species has covered the entire UK coastline over three decades. The programme has shown major changes in abundance of climate-sensitive and habitat-forming species, and revealed shifts in distribution consistent with expectations from climate warming. We present an analysis of the spatial scales of change between the periods 2001-2010, 2011-2020, and post-2020, distinguishing those species whose changes were spatially localised from those which changed over broad scales. Since nationwide coverage was only achieved at sub-decadal timescales, a subset of the survey sites was surveyed annually to allow the assessment of the likely temporal scales of broader scale spatial shifts. Spatial synchrony of species abundance for all annually surveyed sites was calculated using correlations among annual time series. Increases and decreases in abundance were compared among species with different global thermal limits, with the expectation that climate-sensitive species close to their thermal limits would show most change, be more likely to show broadscale synchrony, and more likely to show change correlated with temperature. Finally, understanding the ecological processes underlying such changes and the attribution of change to extreme climatic events such as storms and heatwaves demands higher frequency observations. Monthly observations of fixed locations over a 20-year period in Scotland show long periods of stasis punctuated by rapid changes in cover of fucoid macroalgae following winter storm events. The continued survey programme has fed into national assessments of responses to climate change with approaches developed revealing much about associated changes across the wider North Atlantic.