Over half of the world’s population already lives in cities, with a massive increase in urban population projected by 2050, and an anticipated increase in urban land cover that is about twice the increase in urban population (Seto et al., 2011). Rates of urbanization are spatially uneven, with Asia and Africa projected to account for as much as 86% of projected urban growth (Nations, 2010). Alongside rapid growth, urban shrinkage is also taking place in many parts of Europe and north America (Haase et al., 2012). Urban land change is generally considered one of the most problematic trajectories of land change, due to its perceived irreversibility. In particular, urban land change has severe consequences on climate, biodiversity, ecosystem quality and ecosystem services, which are difficult to mitigate and manage (Elmqvist et al., 2013). Urban green spaces, wetlands and water bodies provide critical biodiversity and ecosystem services that are especially important for poor and vulnerable populations, such as urban slum residents (Nagendra et al., 2013c). Thus, protecting and restoring urban ecosystems is an important issue for sustainable urbanization.
Economic and demographic factors appear as particularly strong drivers of urban land change in China, India and Africa (Seto et al., 2011). African urbanization further constitutes a particular information gap, with studies of land change in African cities being relatively sparse compared to other parts of the world, as a recent meta-analysis indicates (Seto et al. 2011).
Peri-urban regions constitute areas of particularly rapid change that are especially vulnerable to land acquisitions and tenure changes with potentially disrupting socioeconomic effects and ecosystem degradation (Seto et al., 2012a; Seto et al., 2012b), further increasing the social vulnerability of the urban poor, migrants and people practising traditional rural livelihoods. In order to understand, model and manage the multi-level drivers of urbanization in cities and their peri-urban surroundings, recent efforts are beginning to focus on developing a better understanding of urban-rural teleconnections but this requires further elaboration and translation into the implications that this understanding may have on land use planning (Seto et al., 2012b). While urbanization is often seeing as having an adverse impact on land resources and ecosystem service provisioning, a more nuanced view is needed. As an example, Aide and Grau (2004) show that by reducing rural population pressure in areas marginal for agriculture production, rural to urban migration may facilitate the recovery of natural ecosystems while at the same time, the life quality of the rural-to-urban migrants improves. Land change science should aim at a continuous representation of urbanity and rurality across multiple dimensions of livelihood, lifestyle and teleconnectivity, as an advance beyond traditional conceptualizations of an rural-urban gradient or divide (Nagendra et al., 2013b).