Species invasions are a principal component of global climate change, given that they can cause dramatic effects on native species, habitat degradation and subsequent changes in ecosystem functioning. Identifying future invaders and taking steps to prevent their dispersal and establishment represents an enormous challenge to both conservation and international commerce. Shores around the coasts of Ireland and Britain have unique distributions of species that are either at their northern or southern range limits; making it an ideal place test hypotheses about potential invasive species and the impacts of global climate change. Shores in the southwest of Britain are similar to those in Ireland except for the additional presence of the southern limpet P. depressa. P. depressa is currently undergoing range expansion and under current global climate scenarios, has potential to reach Irish shores.

A comparative experiment was done to test whether limpet communities in Ireland would be affected by P. depressa, should it arrive due to climate change. In Ireland, varying densities of P. vulgata and P. ulyssiponensis were transplanted into enclosures in the two habitats: open rock and pools. In Britain, varying densities and combinations of P. vulgata, P. ulyssiponensis and P. depressa were transplanted into enclosures on open rock and in pools. Comparison of identical treatments showed that P. vulgata and P. ulyssiponensis exhibited similar growth rates in the two locations. In Britain, P. vulgata caged in pools with both P. depressa and P. ulyssiponensis showed lower growth rates than when caged in pools with P. ulyssiponensis alone. There was no effect of P. depressa on the growth rate of P. vulgata on open rock or on P. ulyssiponensis. Should P. depressa reach Irish shores, it would directly lower the growth rate of P. vulgata when found co-existing with P. ulyssiponensis in pools.

It was concluded that the potential arrival of P. depressa on Irish shores would have a negative impact on native limpet species. Field-based experimental research in this field is rare. My results revealed that climate change does have the ability to affect key species on rocky shores and the experimental approach we have proposed may be a valuable approach to the difficult task of predicting impacts of climate change.