Leadership Instincts: UW launches Faculty Diversity Initiative  |  Parent Interventions: Participating in engagement schemes improves young people’s wellbeing  |  Teacher Insights: Foreign language learners should be exposed to slang in the classroom   |  Teacher Insights: Site announced for new specialist mathematics school   |  Parent Interventions: New research shows north-south divide in family law  |  Teacher Insights: Lancaster Castle provides focus for lecture on importance of heritage sites  |  Teacher Insights: Tactile books adapted for blind children  |  Parent Interventions: 'Sleep hygiene' should be integrated into epilepsy diagnosis & management   |  International Edu News: University of Birmingham signs up to global UN agreement   |  International Edu News: Credit card-sized soft pumps power wearable artificial muscles  |  Parent Interventions: High fructose diets could cause immune system damage  |  International Edu News: Submit short films to Bristol Science Film Festival 2021  |  International Edu News: Attachable Skin Monitors that Wick the Sweat Away​  |  Parent Interventions: Scientists model a peculiar type of breast cancer  |  International Edu News: NTU Singapore student start-up builds robots for pandemic-proof delivery  |  
January 06, 2021 Wednesday 03:38:04 PM IST

The first-ever study on the characteristics of urbanization in large cities

International Edu News

The world has experienced dramatic urbanization in recent decades.  According to the latest report from the United Nations (UN), the global population in 2018 was 7.6 billion and the urban population was 4.2 billion. By 2050, the global population is expected to soar to 9.7 billion, with 68% of the population living in urban areas.

In the first-ever study on the characteristics of urbanization in large cities around the world, researchers at the Department of Civil Engineering of the University of Hong Kong (HKU) analyzed cities’ urban built-up areas (BUAs) expansion, population growth, and greening BUA changes, and revealed a hugely uneven pace of urbanization in those cities in the last two decades. They warn against major challenges posed to sustainable development if urban problems are not dealt with in a timely manner. The findings have been published in Nature Communications.

The study, conducted by Professor CHEN Ji at the Civil Engineering Department of the Faculty of Engineering, HKU, in collaboration with the Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, and National Supercomputing Center in Shenzhen, analysed the development of 841 large cities throughout the world with BUAs of over 100 km2 (Note 2) based on MODIS satellite data from 2001 to 2018 obtained under the International Geosphere-Biosphere Programme.

Breakdown of the 841 large cities by country income-levels
- 353 cities (42.0%) from high-income countries (e.g. New York in US, Tokyo in Japan)
- 340 cities (40.4%) from upper-middle-income countries (e.g. Pearl River Delta (PRD) and Beijing in China, Sao Paulo in Brazil)
- 127 cities (15.1%) from lower-middle-income countries (e.g. New Delhi in India, Cairo in Egypt, Lagos in Nigeria)
- 21 cities (2.5%) from low-income countries (e.g. Kathmandu in Nepal, Dar es Salaam in Tanzania)

The findings revealed unevenness between built-up areas expansion (BUAE), which reflects the pace of infrastructure development, and urban population growth among the cities; and a widening gap between rapid urban population growth and slow urban greening, represented by features including new parks, green spaces and green roofs.

Cities in the upper-middle-income countries demonstrated the highest BUA expansion, which was more than three times that of high-income countries. Urban expansion and urban population growth in high-income countries remained the lowest. Cities in the low-income and lower-middle-income countries had the highest urban population growth on average, but were substantially lagging behind in BUA expansion and infrastructure development, resulting in serious urban problems such as slums and crowding.

The findings also revealed rapid urbanization of large cities in China in the last two decades. The country had undergone the biggest urban expansion in the period, between 2001 and 2018, its BUA increase accounted for 47.5% of the total expansion in the world. In 2018, the country has 19% of the total BUA of large cities in the world. Of the 841 cities studied, 325 showed significant greening with more than 10% of greening BUAs.  Among them 101 are located in China. The largest greening BUAs are Pearl River Delta (PRD)(Note 3), Tokyo, Yangtze River Delta (YRD, Note 4), Miami, Beijing, Chicago, Seoul, Tianjin, Sao Paulo, and Osaka. In 2018, cities in the highest quarter of greenness range accommodated only 12% of the total city population; about 69% of the total population lived in areas with a lower greenness.


Comments