Simple definitions of peri-urbanization range from the spatial fringe that surrounds the city to more compound ones involving socio-economic processes and dimensions. This historical binary of rural and urban often serve as a barrier to understanding peri-urbanization. Peri-urban regions are complex and interact through distinct geographical and chronological dimensions and phases that are uniquely shaped by socio-economic interests. They are diverse in their characteristics and wide-ranging outcomes and consequently, must not be treated with a ‘one-solution' fashion.
With three-quarters of future population growth occurring in ‘second-tier cities and smaller urban areas' (including peri-urban), attention needs to focus on the sustainability of these regions. For a more specific example, 40 percent of China's growth in the next twenty-five years will be in peri-urban areas. Although peri-urbanization is situational - specifically between most developed countries (MDCs) and least developed countries (LDCs) - there are commonalities among peri-urban areas. Mainly, these fringe areas are in flux. Changing economic and employment structures (from agriculture to manufacturing), rapid population growth due to migrant workforces, rising land costs due to speculation, and a changing development pattern distinguished by mixed land use are the major fluxes within a peri-urban area. These ‘non-continual transition zones' typically lack regulation and development practices and as a result, undergo acute environmental havoc (land degradation, contamination of water and soil, pollution) and social harms (poverty, poor health, less mobility, marginalized rural livelihoods). The piecemeal planning and management lacks an integrative approach that responds to the social, economic, and environmental facets of the peri-urban interface. This is especially magnified within LDC's and is counter-productive to their progress towards sustainable livelihoods.
The intersection of globalization and localization serves as the root of peri-urbanization. The foremost driver of this intersection is capital investment. Industries, mostly manufacturing, are chasing low cost production via value-priced labor. These industries prefer peri-urban areas over existing suburbs due to the need for larger plot size requirements, yet easy access to cities. These industrial clusters are able to work as a liaison between local government and firms and additionally keep all environmental damage in one location. A second driver of peri-urbanization is the region's public policy. Public policies that support peri-urbanization aim to physically and demographically decentralize the city to improve living conditions for the core city and to enhance economic growth, employment, and competitiveness for the region as a whole. With large scale expenditure on infrastructure and a migrating workforce from the rural population, the nationally/regionally induced peri-urban area has to be transferred to a locally governed system. This changeover of stakeholders presents important sustainability matters that if ignored via lack of planning, can fester.
How are cities supposed to prepare for this transition? The variations of a peri-urban area dictate the planning strategies. The mosaic of natural, rural, and urban landscapes, the changing social strata (all with different interests and practices), and overlapping institutions of the area all contribute to this variety. Thus, qualitative and quantitative planning within the region must account for this mosaic within its own chronological and geographical continuum. Policies must be adaptive and responsive on rural, regional, and urban perspectives, and they must create networks among different centers of activity. Overall, peri-urbanization has a high potential for creating discord due to its dynamic fluxes and increasing trend. Optimistically, this means that peri-urban areas also have an influential stake in whether city-regions are sustainable. A new age of planning that emphasizes systems thinking, complexity, and an adaptive, resilient framework is needed. Without such frameworks, peri-urbanization will continue to be socially and environmentally disruptive and unsustainable.