9 - Effect of urban structures on diversity of marine species

Summary

Introduction

As discussed by Chapman and Underwood (Chapter 4), urbanisation is expanding rapidly in estuaries and along the coastlines in all continents across the world. This has led to extremely altered coastal environments, with extensive loss, fragmentation and replacement of natural habitats by built structures (e.g. Mann,1988; Walker, 1988; Glasby and Connell, 1999). Intertidal habitats, which form the interface between the land and the sea, are most strongly affected by urbanisation, because they are frequently disturbed by commercial and recreational activities (e.g. Iannuzzi et al., 1996), or extremely altered by the desire for ‘waterfront’ developments and the need to access the water from the land for transport and travel (e.g. Yapp, 1986).

Intertidal mangroves (Young and Harvey, 1996) and saltmarshes (Zedler, 1988) have received most attention with respect to urban development because their loss is immediately obvious and because they can provide habitat for rare or endangered plants or charismatic vertebrates (Zedler, 1993). Intertidal and freshwater wetlands suffered particularly severe loss and fragmentation over many years because they were considered wastelands and, thus, ‘reclaimed’ for urban development. Fortunately, in some parts of the world, this process is being reversed by active programmes of mitigation and restoration (Zedler et al., 1998).

Similarly, changes to subtidal seagrass meadows have received attention because of their perceived value as nursery grounds for commercially important fish and crustaceans (Robertson and Duke, 1987; Haywood et al., 1995). In many urbanised estuaries, seagrasses have declined because of overgrowth by algae (Short and Burdick, 1996).