The process of urbanization describes a shift in a population from one that is dispersed across small rural settlements in which agriculture is the dominant economic activity towards one where the population is concentrated in larger, dense urban settlements characterized by industrial and service activities. It is the most significant human activity process since the 20th century. According to the numbers reported by United Nations, the proportion of the global urban population increased from less than 30% in 1950 to 54% in 2014. It is predicted that the proportion will reach 66% by 2050. Urbanization trends are closely related to sustainable development. Under appropriate planning and management, the concentration of population in urban dwellings can promote economic and social development. However, rapid and unplanned urban development without construction of necessary infrastructures is a threat to sustainable development. The United Nations Sustainable Development Summit was held in New York in September 2015, it has adopted the 2030 Agenda for Sustainable Development, which announced 17 sustainable development goals and one of them is to make cities and human settlements inclusive, safe, resilient, and sustainable. Facilities connectivity is a priority area for implementing the Belt and Road Initiative. The development of core cities and coastal cities are crucial for facilities connectivity and construction of a new Eurasian Land Bridge and developing China-Mongolia-Russia, China-Central Asia-West Asia, and China-Indochina Peninsula economic corridors. The Urbanization Task Force of DBAR aims to develop technologies to derive human settlement information with earth observation data, generate products on human settlement dynamics, analyze and assess urban development and its impacts along the Belt and Road. These efforts can support decision making of governments to promote sustainable urban development and facilitate addressing environmental and social challenges presented by urbanization along the Belt and Road. It can also play an important role to support the UN sustainable development goals, the New Urban Agenda and the UN Framework Convention on Climate Change.

Research Progress

The Belt and Road area in our study includes more than 60 countries, which are located in Asia, Europe, and North Africa. The urbanization rate is an indicator to measure the condition of socio-economic development. It can be defined as the percentage of population that is living in urban areas. The urbanization rates and large agglomerations in the countries along the Belt and Road as derived from the UN World Urbanization Prospect are illustrated in Figure 1. The total population of the countries is 4.7 billion with 2.3 billion living in urban areas. The average urbanization rate is 47.9%, which is lower than the global average of 54%. Only 14 countries have an urbanization level higher than 75%. Four countries, Singapore, Qatar, Kuwait, and Israel, have the highest urbanization level above 90%. 21 countries have an urbanization level lower than 50%. Sri Lanka, Nepal, Cambodia, Afghanistan, and Tajikistan have the lowest urbanization level which is below 30%. During the period of 1990–2014, Asia experienced a rapid urbanization process. The urban population in Asia increased from 32.3% in 1990 to 47.5% in 2014. Five countries, Laos (3.7%), Bhutan (3.5%), Nepal (3.0%), China (3.0%), and Indonesia (2.3%) have experienced highest growth rate of urbanization level. China, India, Indonesia, Pakistan, and Bangladesh are most populous countries in the Belt and Road region. Their urbanization levels are 54%, 32%, 53%, 38%, and 34% respectively. In 2015, there are 501 large agglomeration globally with 274 located in the Belt and Road area. Among them, 17 are megacities with more than 10 million inhabitants (Figure 1).

Accurate, consistent, and timely data on global trends in urbanization is a key input to better assess current and future needs with respect to urban growth and to set policy priorities to promote inclusive and equitable urban and rural development. Due to its synoptic, repetitive, and consistent observation, satellite-based Earth observation (EO) technology can be potentially relevant for monitoring the evolution of artificial built-up surfaces, urban area mapping, urban land cover change monitoring, urban environment, and morphology analysis at national, regional, and global scales. Urban built-up area is an important measure in urban landscape, and key variable for understanding ecosystem and social economic process in urban system. Since 2000, several global human settlement or built-up area products have been produced with earth observation data. Cooperating with the Joint Research Centre (JRC) of the European Commission and other international organizations, the spatial pattern and dynamics of urban areas were derived from EO data, and urban expansion and urbanization process were explored along the Belt and Road. Figure 2 shows the DMSP/OLS night light images along the Belt and Road in 1992 and 2013. Their differences reflect the urbanization process in the countries along the Belt and Road.

The changes of average night light intensity and total population in 10 most populous countries from 1992 to 2013 were illustrated in Figure 3. An increasing trend is observed for all the countries except Russia.

India as one of the countries with largest concentration of megacities in the world has endured a rapid urbanization process in recent decades. Based on the built-up area extracted from remote sensing images, Figure 4 shows the changes of total built-up area and population in the eight countries in South Asia. During the past four decades, the total built-up area has increased with the population growth. From 1975 to 2015, the built-up area in India increased most by 25 172 km², followed by an increase of 3 764 km² in Pakistan. Bangladesh's total built-up area increased by 5 times since 1975, and Sri Lanka increased by 4 times.

Figure 5 shows the changes in the built-up per capita in South Asia. The global average of built-up per capita is 106 square meters in 2015, and for low-income countries and regions, it is 44 square meters. Among the lower-middle-income and low-income countries in Figure 5, only Sri Lanka shows a built-up per capita above the average level.

Figure 6 shows the spatial pattern of urban expansion in six mega cities in South Asia. The built-up areas of Kolkata and Mumbai were large in 1975, and then gradually expanded to the surrounding areas. From 1975 to 1990, the built-up areas of Delhi, Dhaka, and Mumbai increased a lot. The urbanized area increased significantly in Bangalore from 2000 to 2015.

Central Asia consisting of Kazakhstan, Uzbekistan, Kyrgyzstan, Turkmenistan, and Tajikistan is located in the Eurasian continent hinterland. It is an indispensable part of the ancient Silk Road and the starting point of the Silk Road Economic Belt outside China. Figure 7 shows the spatial expansion of the five major cities in Central Asia, Tashkent, Bishkek, Almaty, Dushanbe, and Ashgabat.

Figure 8 shows the changes of built-up density and population in the five major cities in Central Asia from 1975 to 2015. The built-up density and population grew fast in Tashkent from 1975 to 1990. The population in Bishkek has been increasing rapidly since 1975, and the density of builtup areas increased significantly since 2000. The built-up density grew rapidly from 1975 to 1990, and the population began to grow after 2000 in Almaty. From 1975 to 1990, the population increased and the city expanded in Dushanbe. The built-up density and population had been increasing during the past four decades in Ashgabat.

Moscow is the capital and major political, economic, cultural, scientific, and traffic center of Russia, as well as the second most populous city in Europe. Its population accounts for one tenth of the total population in Russia. Figure 9 shows the expansion of urban areas in Moscow from Landsat satellite imagery. The urban area in Moscow increased from 711 km² in 1975 to 1 795 km² in 2015.

Perspective Activities

With the rapid development of sensor technology and spatial data mining methods, more remote sensing data and derived spatial information are becoming available. Based on high spatial resolution, high temporal resolution and hyperspectral multi-source remote sensing data, large-scale urban spatial information products will be developed. The urbanization process and its impacts on population, resources, and environment will be investigated in order to assist the urban planning and urban management and facilitate urban health development and construction of eco-cities, thereby supporting the construction of the Belt and Road strategy and the UN sustainable development goals.

Task Leaders and Members

Comments: Rapid urbanization comes with a set of challenges such as increasing inequalities, migration, environmental degradation, risks from disasters and climate change. To cope with these problems, sustainable and inclusive model of urbanization should be implemented. DBAR Urbanization Task Force is a platform for international cooperation in science and technology to promote sustainable urban development in countries along the Belt and Road.

Comments: Earth observation is a promising measurement system to address the assessment of human settlements from local to national and global scale. The Global Human Settlement framework produces global spatial information about the human presence on the planet over time. As detailed, measurable and globally consistent descriptions of human habitat, it can support global awareness on urbanization trends and dynamics and enable the implementation of the New Urban Agenda.

Comments: The Belt and Road region is comprised of more than 60 countries in the world. How these countries develop affects not only their residents but also the global economy. New forms of data allow better monitoring and understanding of urban trends. With improved understanding of what is happening on the ground, policy makers will be better able to promote sustainable urban development as well as improving resilience. Already spatially linked, the Digital Belt and Road Initiative provides a platform for collaboration on these important topics.

Comments: As the world's population continues to urbanize, it is important for urban development to be guided by a sustainable planning and long-term management vision. The sustainable and environmental design of land use and urban spaces can create a balance between the built and natural systems to improve urban human living. Through a close collaboration of international partners, I reckon the DBAR Urbanization Task Force will continue to work on urban data development to facilitate cross-disciplinary knowledge sharing towards a more sustainable future along the Belt and Road.