Assessment of urban growth dynamics using landscape expansion index: A study of 514 metropolitan cities from 1975 to 2020

Understanding urban growth dynamics is essential for assessing urbanization impacts, guiding long-term planning, and optimizing infrastructure development. This study examines urban growth across 514 metropolitan cities using Global Human Settlement Layer data from 1975, 1990, 2000, 2015, and 2020. The Landscape Expansion Index identifies three dominant growth patterns: edge expansion, infill growth, and outlying growth. The study findings reveal that edge expansion dominates North America and China, driven by policy and infrastructure investments. Infill growth is most prominent in South and Southeast Asia, particularly in high-density cities like Tokyo and Singapore, where rising land prices encourage vertical development. Outlying growth is widespread in African and Indian cities due to rapid population growth and affordable peripheral land. Europe and South America exhibit stable edge expansion from 1975 to 2020, reflecting slower urbanization. The Middle East and the Rest of Asia display mixed growth patterns influenced by ongoing urbanization and rising population demands. Oceania experienced outlying growth from 2015 to 2020 in expanding urban peripheries. The study highlights factors influencing urban growth, such as mean elevation, which negatively impacts urban growth, while proximity to water bodies increasingly facilitates expansion, particularly in coastal cities. Surrounding land availability limits outlying growth expansion and encourages densification. The analysis shows that edge expansion and infill growth exhibited significant vertical growth. The infill growth surged from 1.68 in 1990 to 3.21 in 2020, while edge expansion increased from 0.59 to 1.87 over the same period. Outlying growth displayed the lowest vertical growth, rising from 0.10 in 1990 to 0.90 by 2020. These findings highlight the need for strategic planning to balance growth and align development with environmental constraints for resilient cities. The present study provides valuable insights into the complex dynamics of urban growth and urban planning.