Monitoring and assessing the growth law of urban land using multi-source data: A case study of five East African countries

With the rapid growth of the world's urban population, urban land expansion has become an inevitable trend, with Africa being one of the primary locations for both global urban population growth and urban land expansion. Small and medium-sized cities are gradually recognized as playing an important role in the urbanization process in Africa. However, there is relatively little attention has been paid to small and medium-sized cities. This study focused on urban clusters in Kenya, Tanzania, Uganda, Rwanda, and Burundi, five countries in East Africa. Urban land and urban centers of 59 cities were identified using multi-source data. Then, the growth law of cities of different sizes (large, medium, and small) was analyzed through the urban land density function and urban attractiveness index. Results indicate that large cities are more developed, with obvious core areas and high attractiveness, which may lead to further excessive urbanization and pose challenges to urban sustainable development. Small cities are still in the early stages of urban development and are experiencing rapid and disorderly expansion. By reviewing the history of urban development and policy implementation, we believe that promoting the development of small and medium-sized cities is a significant measure to slow down the excessive urbanization of large cities. Increasing employment opportunities and infrastructure is an effective way to enhance the attractiveness of small and medium-sized cities and promote their development. At the same time, it is necessary to carry out urban plans for small and medium-sized cities to avoid phenomena such as informal settlements that affect the sustainable development of large cities.