دانلود رایگان مقاله تنوع زیستی پنهان در زیستگاه مرموز توسط سازه های دفاع ساحلی متخلخل

Abstract

In response to flood risk from rising and stormier seas, increasing amounts of natural coastline worldwide are being replaced by a proliferation of coastal defence structures. While the primary role of defence structures is protecting the coastline, consideration should be given to the biological coastal communities they support. Artificial structures are currently seen as poor habitats for marine organisms. They are constructed in harsh coastal environments, lack structural complexity, and are subjected to episodic disturbance from maintenance, reducing their suitability as habitats for coastal species. Recent work has focused on mitigating the impacts of coastal defence structures, through secondary routes such as enhancing biodiversity by encouraging colonisation of marine biota. Research thus far has focused on enhancements to improve structural complexity on the external surfaces of coastal defences. Many structures are porous with internal compartments. To date no work has been undertaken on the habitat provided by the internal surfaces of the blocks used in building structures. We investigated the role of porous coastal defence structures in habitat provision. Taking advantage of a groyne reduction from 45 m to 20 m length, we surveyed the internal environment of the structure. We also considered the impacts of maintenance activity on coastal assemblages. Our work shows that the internal environment of artificial structures provides functional habitat space supporting higher species richness and diversity than external surfaces. The more benign environment of internal surfaces protects from desiccation stress and is probably less scoured by mobile sediments, and as such is of unrealised importance to coastal assemblages. External surfaces are also subject to high levels of disturbance from maintenance activities, further limiting the potential ecological contribution this area of the artificial habitat might otherwise develop. These findings reveal the multifunctional role of porous coastal defence structures, acting as engineering protection and habitats for coastal assemblages.

5. Concluding comments

Until now, the internal environment of CDS has not been actively considered or explored by ecologists for its potential to provide habitat and enhance biodiversity. Our study highlights the importance of these hidden environments for coastal species, suggesting that porous CDS provide improved habitat heterogeneity and refuges via internal compartments. These features are not present in solid structure designs with no internal compartments. External environments on coastal defence structures are exposed to intense environmental pressures made worse by anthropogenic disturbance from any maintenance work. Therefore they only support a small number of hardy species. Focus must be turned to the internal environment, which can support a higher diversity of species. Porous structures, a common coastal engineering design, are not only effective in engineering; they are also considerably more effective for biodiversity than previously realised. Porous CDS should be considered more widely in future coastal engineering schemes, to encourage settlement of coastal species and to sustain coastal communities, particularly given the growing number of artificial structures and in light of gross environmental change and habitat loss. Finally, further investigations into the impacts of maintenance activity on coastal assemblages should be considered to inform coastal engineers and to provide evidence-based decisions for effective coastal defence management regimes.