29 - Valuing urban wetlands: modification, preservation and restoration

Summary

Introduction

The increasingly rapid rates of land-cover and land-use change driven by the growth of suburban and urban areas threatens the sustainability of the world's natural resources. And nowhere has this phenomenon been more evident than in the world's coastal regions (Chapman and Underwood,Chapter 4). Urbanisation of the world's coastal area is accelerating (Tibbetts, 2002). Two-fifths of the world's major cities inhabited by 1–10 million people are located in coastal regions. One hundred per cent of cities with populations over one million in South America are coastal and 75% of those in Asia and Africa are as well (Berry, 1990). In the United States, coastal areas represent 53% of the population but only 17% of the land area (Pew Oceans Commission, 2003).

The rapid development and population growth associated with coastal areas is leading to the destruction and degradation of important habitats including wetlands, estuaries and coral reefs. It has been estimated that when 10% of the area of a watershed is covered in roads and other impervious surfaces, then rivers and streams and downstream coastal waters become degraded (Pew Oceans Commission, 2003).

The impacts of urbanisation on aquatic systems and especially streams are well documented. Urbanisation and associated stormwater runoff threaten receiving water systems (Watson et al., 1981; Schueler, 1987; Mensing et al., 1998; Magee et al., 1999; Reinelt et al., 1999; Shaffer et al., 1999; Groffman et al., 2003).