Anthropogenic pressures related to urbanization are primary drivers behind an unprecedented degree of habitat loss and degradation on a global scale, precipitating a rate of species loss that exceeds the background extinction rate observed in Earth’s pre-human geological and biological history by an estimated magnitude of 100 to 1000 times. Thus, an improved understanding of how to effectively minimize the inevitable ecosystem effects of urban growth is of critical importance to addressing the global biodiversity crisis. Aspects of the built up landscape including housing density and total amount of development have been studied extensively, but relatively few studies have analyzed the ecosystem effects of spatially explicit patterns of urban form. Compact urban forms intensely concentrate activities within one centralized location, leaving a greater proportion of the surrounding landscape intact. Dispersed urban forms (“sprawl”) distribute disturbances more evenly across the landscape. In ecology and other applied disciplines, systematic reviews are considered critical to the development of evidence-based frameworks to support decision-making and, despite being deeply relevant to biodiversity conservation, the current state of knowledge regarding the ecosystem effects of urban form had not yet been assessed. Our study, which sought to (1) determine whether compact versus dispersed urban form has higher ecological value and (2) to identify knowledge gaps and recommend future directions for related urban ecological studies, addressed the urgent need for such a review.
Results/Conclusions
A small albeit increasing number of studies investigating ecosystem response to spatial patterns of development corroborate an intuitive assumption: compact urban forms are generally preferential to urban sprawl with regard to maintaining ecosystem structure and function and, subsequently, native biodiversity conservation. In particular, the overwhelming majority of studies linked dispersed urban forms to declines in native biodiversity, increased landscape fragmentation, decreased habitat connectivity, and diminished ecosystem function, and recommend concentrating urban development to reduce the negative impacts of urban sprawl on biodiversity. Our review also revealed a strong preference for modeling over empirical research, inconsistencies in characterizing and measuring urban form across studies, and strong biases with respect to biome, geographic area, and selected response variables.