ABSTRACT

Many studies have demonstrated that there often exists a gradient of change in species diversity and abundance along an urban-suburban-rural gradient, with peaks in suburbia, supporting the intermediate disturbance hypothesis. At Palo Alto, California, for example, species richness and diversity of both birds and butterflies peak at intermediate levels of urban development; bird abundance was also greatest in suburbia, but butterfly abundance declined with increasing building development (Blair 1996, 1999; Blair and Launer 1997). Similar trends have been noted for birds in other countries, for example in Dunedin, New Zealand (Van Heezik et al. 2008), and for other animal groups, for example rodents in Buenos Aires, Argentina (Cavia et al. 2009) and carabid ground beetles in Debrecen, Hungary (Magura et al. 2008). Lizard abundance and species number in Tucson, Arizona, also decline along a five-point scale of increasing housing density (Germaine and Wakeling 2000). Generalist species tend to be more abundant in more urbanised areas. Seasonal effects must also be considered, many birds for example making broader use of the urban landscape in winter, even in Mediterranean towns, such as Montpellier, France, where the urban heat island is not especially pronounced (Caula et al. 2008).