Biodiversity climate change impacts report card technical paper:10. Implications of climate change for coastal and inter-tidal habitats in the UK

Executive summary - Coastal habitats are complex, dynamic and interdependent. They are important in providing sea defences, areas for recreation, biodiversity and a range of other ecosystem services. - Increased air- and sea-surface temperatures have resulted in changes in the distribution of marine and coastal species. Both warmer- and colder-water species are shifting northwards. However, warmer-water species are shifting northwards faster than colder-water species are retreating, resulting in changes in community composition. Changes in the abundance of keystone taxa can cause a cascade of responses, further altering community composition. - Changes in the phenology of coastal species have been observed, with the rates of change in marine species being considerably greater than those in terrestrial and freshwater systems. Recent advances in the phenology of species have not all occurred at the same rate, in some cases resulting in mismatches of timing of annual cycles of animals and their food organisms. - Changes in precipitation are likely to affect coastal habitats, but the projected increase in winter rainfall and decrease in summer rainfall will tend to have opposing effects; the net result of these is not known. High winter rainfall and milder winter temperatures may extend the growing season and lead to faster succession and dominance by taller competitive plant species. This will be exacerbated by anthropogenic nutrient enrichment. However, increasing frequency and severity of summer droughts may counteract the effects of nutrient enrichment and winter precipitation. Increased drought will have impacts on habitats that are highly dependent on the maintenance of hydrological regimes, such as machair lochs and dune slacks. - Rising sea levels have been associated with the loss of coastal habitats. Predicted future rises will have significant impacts on coastal and intertidal habitats, including changing geomorphological processes, further habitat loss and increasing the vulnerability of infrastructure. However, coastal systems are dynamic and have the potential to adapt to rising sea levels, but only if there is an adequate supply of sediment to allow accretion and if there is landward space for the coast to roll-back into. Sea defences and other coastal management interrupt the movement of sediment between systems and prevent natural coastal realignment. - Managed coastal realignment is beneficial because it offers the potential to create habitat and provide flood defence benefits. Inevitably, there will be conflict between the need to maintain intertidal and other coastal habitats (e.g. saltmarsh, mud flat and sand dune) by realignment, and the need to protect valuable inland coastal habitats, such as grazing marsh and saline lagoons. - Future changes in coastal habitats are hard to predict because it is difficult to separate the impacts of rising sea levels from those of coastal management, including sea defences. Coastal zone management and adaptation, and the interactions with other climate drivers, nutrient deposition and habitat management, will have significant influence on the quantity, quality and location of future coastal habitats