Sensitivity of intertidal reef biotopes to human activities

Sensitivity to human activities

Introduction

An important theme of this report is that the community structure of some intertidal reef biotopes is highly variable in space and time. Against this background of natural variation, human impacts may not be detectable without detailed and, often, long term investigation (Stewart-Oaten et al., 1986, Underwood, 1991). Nor should observed changes be automatically attributed to anthropogenic disturbance. However, because of the dynamic nature of rocky shore communities, impacts on one species can have community-wide influences.

The purpose of this chapter is to review current understanding of anthropogenic impacts on rocky shore community structure and dynamics and the ability to distinguish these from natural changes. Natural physical disturbance is a common and often important factor affecting the structure and dynamics of rocky shore communities. Anthropogenic disturbances will be particularly damaging when they are sustained (chronic) or of high intensity (acute). Intertidal and littoral ecosystems are exposed to human impact more frequently than any other marine system (Schramm, 1991). Rocky shore communities and species are sensitive to both acute impacts, such as oil spills, and chronic impacts, such as those from TBT-based paints and recreational activities. The responses of communities to these impacts are often well studied and documented, enabling conservation strategies to be suggested. Other anthropogenic impacts on rocky shore communities include the introduction of non-native species and the potentially positive effect of increased habitat provision through building of sea defences.

While this chapter contains a discussion of some of the most notable human impacts on rocky shore communities, it is not intended as an exhaustive guide. Any human activity which alters the physical, chemical or biological nature of the coastal environment should be regarded as having the potential to impact rocky shore communities. A more comprehensive account of the sensitivity of marine communities to human activities is given by Holt et al. (1995).