Improving habitat heterogenity on coastal defence structures.

Abstract

Sea level rise and higher storm frequency is increasing the need for hard coastal defences worldwide. The majority of these structures lack optimal habitats for intertidal species, resulting in low diversity. Here, we evaluate low-cost enhancement techniques which increase habitat heterogeneity and surface texture on different rock types. Arrays of holes and grooves inspired by ‘blast features’ produced during the quarrying process were created on both granite rock armour and limestone rock groynes in two locations in England. After 12 months the treatments were successful at attracting new species to the defence structures and increasing the overall diversity and abundance of organisms. Mobile fauna including crabs and fish were recorded utilising the holes and grooves. Non -native species were recorded in grooves at one site but in no greater abundance than control areas. At the southern site, species known to be spreading in response to climate changes were found in both treatments but not in controls. The cost of these treatments was low in relation to that of the defence scheme and could be easily replicated either during or after construction. Through evaluatio n of the use of these ecological enhancement techniques on coastal structures, we suggest that they have considerable potential to enhance local patterns of biodiversity when used within large -scale defence projects.