Urban Ecosystems and Island Biogeography

Abstract

In urban areas, continuing fragmentation of natural habitat, disturbance, and increasing isolation of individual ‘habitat islands’, has brought on almost general reduction in species richness. Sensitive species are being replaced by aggressive synanthropic ones. Continued loss seems inevitable, but reducing the rate of that loss is a worthwhile conservation goal. It is imperative that the numerous and varied habitats within each urban area be considered as interrelated and not as separate units. Island biogeography models supply the means for unifying the disparate elements in urban ecological studies and can provide a useful strategy for conservation.It is difficult to define colonization, extinction, and equilibrium, in disturbed, often transient, urban habitats. Pseudo- and successional turnover dominate. The occupation of each ‘habitat island’ is a function of its own geography and of its position relative to other ‘islands’. Each habitat may serve as isolated ‘island’, ‘stepping-stone’, or ‘corridor’, depending on its spatial relationships with other ‘habitat islands’ and with the nature of each organism present.‘Habitat islands’ in small cities appear to function like large or near oceanic islands, while those in large cities seem to respond like small or distant oceanic islands. In all cases, the analogy with land-bridge islands is appropriate. Continuing urbanization is leading to reduced ‘habitat island’ size, and increasing the isolation of units from one another and from the surrounding rural ‘reservoir’.

Aphids (Hemiptera: Aphidinea) and ground beetles (Coleoptera: Carabidae) in the urban environments of Bydgoszcz and its vicinities

“…In town ecosystems, in turn, urbanization to a large extent eliminates typical habitats of various animal species and drives out the fauna living there previously. Retaining the existing urban green and creating de novo aeras of this type within the limits of towns and in their protection zones, which would enable a further development of networks of the above-mentioned so-called ecological corridors, is of essential importance in the processes of shaping the urban environment (Davis and Glick, 1978). Such biologically active areas, with a relatively high species diversity, can make a food base and provide places of living and nesting for groups of organisms inhabiting them in urban environments.…”

Spectral analysis of flowers used by nectar-feeding birds in an urban area in Southeastern Brazil

“…The landscape of an urban centre consists of a mosaic of built-up areas, gardens, parks, yards and rare fragments of native forest (Davis and Glick, 1978;French et al, 2005). Native vegetation areas are usually replaced by other exotic and native species with better aesthetics, landscaping and commercial performance (Beissinger and Osborne, 1982;DeGraaf, 1985).…”

The vegetation requirements of Superb Fairy-wrens (Malurus cyaneus) in non-urban edge and urbanised habitats

“…Within the urban matrix a range of habitats may be tolerated by a species, and fulfil different requirements such as foraging or breeding . Local factors play a significant role in the structure of habitat occupied by individuals (Davis and Glick 1978;Fernández-Juricic 2000), though the requirements of a population must be met at a landscape scale in order to sustain the population (Wiens 1985;Clergeau et al 2006). Therefore, understanding the habitat requirements of individuals at a small scale is a vital first step for managing the landscape and promoting the survival of less common species (Savard et al 2000).…”