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Urbanization is one of the most important land conversion processes around the world (Haase et al., 2018). Conventional wisdom has it that high population growth rate is the major underlying driver behind the rapid growth of cities (Jat et al., 2008; UNEP 2010). The standard way of thinking about urbanization is that people will drift from rural to urban areas in search of better economic opportunities, access to infrastructure and improved social services (Adepoju, 2018). As this drift occurs, the consumption of resources in cities is expected to more than double from 40 billion tons in 2010 to an unsustainable level of 90 billion tons in 2050, according to a recent study by the IRP (2018). Today, urban areas are home to 55% of the world’s total population, with Africa contributing 13% of the 4.2 billion global urban population (UN-DESA, 2018).
There is an undeniable close correlation between urbanization and the three dimensions of sustainable development: economic, social and environmental (Cobbinah and Erdiaw-Kwasie, 2018; UN-DESA, 2018; Yan et al., 2018; Lawrence, 2019). On the one hand, well-planned urbanization can improve living conditions of city dwellers, create an enabling environment for socio-economic development, and enable growth of the middle class (Kayizzi-Mugerwa, 2014; Zhou et al., 2015). Numerous case studies exist where cities have improved sustainability and enhanced the positive impacts of urban development through strategic planning tools and green plans that focus on key sustainability target areas such climate change and energy, land and water conservation, public spaces, air quality management, waste management, and mobility (see for example, Yigitcanlar, 2008; Shen et al., 2011). On the other hand, negative consequences of rapid and unplanned urbanization are widespread and well documented in both developed and developing countries. For example, early urbanization experiences in the 1930s and 1940s in developed countries such as the United Kingdom and the United States saw the widespread destruction and conversion of farmlands to urban areas (Firman, 1997). Similarly, recent studies have documented unplanned land conversion and urban development challenges experienced in many developing country cities, including the deterioration of public services, propagation of slums and the informal sector, saltwater intrusion of coastal aquifers, environmental impacts on riparian and coastal habitats, and widespread urban poverty (UNEP, 2010; Kayizzi-Mugerwa, 2014).
Other widely cited problems resulting from uncontrolled urbanization and unsustainable land use change practices include decaying of urban infrastructure, uncontrollable growth of informal settlements, climate change, loss of agricultural land, air pollution, traffic congestion, and the destruction of ecosystems (Huang et al., 2009; Youssef et al., 2011; Zhou et al., 2015; Shen et al., 2017). In fact, the study by Verburg et al. (2006) identifies urbanization as one of the leading threats to the elimination and eventual extinction of large numbers of native species of living organisms. In Steyl and Dennis (2010), a significant drop in the water table and consequent seawater intrusion experienced in the North African coastal countries of Libya, Tunisia, Algeria, Morocco and Egypt has been attributed to land conversion factors that include rapid urbanization, agricultural water consumption, and periodic droughts. Given this multiplicity of impacts, there is growing interest in using geospatial technologies in research to help map and monitor both spatial and temporal land conversion trends, especially in urban areas.