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Key Findings

  • Range extensions have occurred at the northern limits of the geographical distributions of typically southern, warm water species Osilinus lineatus (toothed topshell), Gibbula umbilicalis (flat topshell), Chthamalus montagui (Montaguís stellate barnacle), Chthamalus stellatus (Poliís stellate barnacle) and Balanus perforatus (acorn barnacle) since the mid-1980s in Wales, Northern Ireland and Scotland, including greater penetration around the north of Scotland into the colder North Sea. It is likely that these northward range extensions have occurred in response to climatic warming increasing reproductive effort and juvenile survival success allowing these species to establish on suitable habitats.
  • Eastward range extensions of the southern species Osilinus lineatus (toothed topshell), Gibbula umbilicalis (flat topshell), Patella ulyssiponensis (china limpet), Patella depressa (black footed limpet), Melarhaphe neritoides (small periwinkle), Actinia fragacea (strawberry anemone) and Balanus perforatus (acorn barnacle) have also occurred since the mid-1980s in the English Channel beyond previous biogeographic boundaries. It is likely that these range extensions have occurred due to a combination of the proliferation of artificial sea defences along this coast providing suitable habitat where none was previously present and greater recruitment success of southern species in response to climatic warming.
  • The northern species Alaria esculenta (dabberlocks) and Tectura testudinalis (common tortoiseshell limpet) have shown small retractions in their southern distributional limits and declines in abundance at populations close to these range edges, but the rate of recession is not as fast as the rate of advancement in southern species.
  • Fluctuations of the northern barnacle Semibalanus balanoides and the southern Chthamalus spp. have been related to climate change, using historical data collected by Southward and advanced statistical methods. These show that there is a direct negative effect of warm springs on survival of Semibalanus balanoides which via release from competition has an indirect positive effect on Chthamalus. These data have been used for hindcast and forecast modelling using UKCIP climate scenarios. In particular these models have been able to incorporate characteristics such as species mortality, larval supply and competitive interactions to create more biologically realistic predictions of species responses to climate change.
  • Models using the extensive broadscale resurvey data have been created for all MarClim indicator species to predict changes in their abundance and distribution in response to wave action and sea surface temperature regimes forecast by UKCIP.