A Narrative Literature Review: What Is the Ideal Density for Environmentally Sustainable Urban Growth?

Urban growth in the form of sprawl became a global planning problem in the 20th century. High urbanization rates in combination with low-density zoning regulations put additional pressure on growing cities. Sprawl continues to generate negative social, environmental, and economic impacts. The results of 20 studies presented in this narrative review, which observe the change in urban form over time, indicate that the current urban growth form is sprawl. Compact urban form is considered a sustainable form of urban growth in the literature. The results of 10 studies on the correlation between the urban form and carbon dioxide (CO2) emissions show that densification without provision of adequate access to public transportation will induce more traffic, congestion, and associated CO2 emissions. The ideal density is subject to adequate access to public transportation-that is, mass transit-supportive density. Environmentally sustainable densities cannot deliver detached housing as a housing mode in many countries. International agreements on CO2 emissions should be translated and implemented at the metropolitan and municipal levels of governance via tools that have statutory powers. Statutory instruments such as planning schemes, building codes, and planning and environmental acts incorporating precinct-sustainable assessment systems (Building Research Establishment Environmental Assessment Method (BREEAM) Leadership in Energy and Environmental Design (LEED) Comprehensive Assessment System for Built Environment Efficiency (CASBEE, and Green Star) provide the opportunity to endorse sustainable density objectives.

Automated summary

Urban sprawl and low-density zoning regulations have put pressure on urban growth, causing negative impacts. Compact urban form is considered a sustainable mode of growth. Research shows that densification without adequate public transportation access leads to more traffic, congestion, and CO2 emissions. Environmentally sustainable densities cannot accommodate detached housing. International agreements on CO2 emissions should be implemented at the metropolitan and municipal levels with statutory tools.