This special issue examines how cities in the Global South can predict & manage their expansion in effective, sustainable ways.

Urban population growth, now largely confined to the Global South, requires cities to implement effective strategies to accommodate many more people and to ensure that they live productive, healthy, and satisfying lives. The limited potential of infill and densification inevitably requires the conversion of very large areas in the surrounding countryside to urban use. This special issue considers how this can be done in an orderly, efficient, and inclusive manner, with conservation and climate change in mind.

Guest Editor: Shlomo (Solly) Angel

Making room for accommodating growth in cities is a two-pronged strategy: facilitating and promoting densification while, at the same time, preparing lands at scale for sustainable urban expansion in their periphery. Urban expansion in geographic space is often ill-defined and its measurement and projection into the future are controversial. 'Sprawl' is detrimental to the surrounding countryside, costly in terms of infrastructure, excessive waste in energy and resources, and increased GHG emissions. But the regulatory containment of urban expansion is problematic as it can result in land and house price inflation, making cities less affordable. When regulation or enforcement are weak, expansion occurs in a detrimental manner.

There is a window of opportunity currently that allows cities in the Global South to guide and shape their form-making them more productive, more inclusive, and sustainable while they are growing. Preparing for urban expansion with climate change in mind can ensure that expansion is not car-centric and that expansion areas are planned with broader Sustainable Development Goals (SDGs) in mind.

This special issue explores:

• whether and where preparing for urban expansion is appropriate
• how urban expansion can be undertaken more sustainably
• how and where expansion needs to be contained
• what are the appropriate strategies for balancing densification and expansion
• how the appropriate expansion strategies can be effectively implemented.

Lessons and guidance are provided for improved anticipation and planning for urban expansion. A sensible strategy is to prepare lands for expansion, and to prepare them with climate change in mind. As this special issue makes clear, this involves planning for expansion by focusing on simple strategic measures that local authorities can undertake (e.g. arterial roads, removing obstacles to transit-oriented densification along these arterial roads, facilitating land subdivision with small blocks, an adequate amount of land in streets in both formal and informal neighborhoods, protecting areas of high environmental risks as well as ecological assets from development, and ensuring the creation of a hierarchy of green public open spaces).

Urban expansion should not be perceived as an unpleasant burden to be avoided, resisted, or ignored. Instead, it is an opportunity and a challenge, with multiple benefits to be realized in coming decades if done correctly.

Table of Contents

Urban expansion: theory, evidence and practice
Shlomo Angel

Complexifying urban expansion: an exploratory, gradient-based approach
Steven M. Richter, R. Patrick Bixler

Urban growth in peri-urban, rural and urban areas: Mexico City
Gustavo Manuel Cruz-Bello, José Mauricio Galeana-Pizaña, Salomón González-Arellano

Urban encroachment in ecologically sensitive areas: drivers, impediments and consequences
Manja Hoppe Andreasen, Jytte Agergaard, Richard Yao Kofie, Lasse Møller-Jensen, Martin Oteng-Ababio

Socioeconomic and livelihood impacts within Bangkok's expanding metropolitan region
Gregory Gullette, Paporn Thebpanya, Sayamon Singto

Planning gaps: unexpected urban expansion in five Colombian metropolitan areas
Maria Monica Salazar Tamayo, Johann Dilak Julio Estrada

Implications of urban expansion: land, planning and housing in Lagos
Basirat Oyalowo

The urban expansion of Berlin, 1862-1900: Hobrecht's Plan
Felix Bentlin

The Ethiopia Urban Expansion Initiative and knowledge exchange
Patrick Lamson-Hall, Richard Martin