McHarg’s theory and practice of regional ecological planning: retrospect and prospect

Abstract

Ian McHarg’s theory of regional ecological planning is a milestone in the history of planning and socio-ecological practice. The use of science—geology, physiography, soils, hydrology, and vegetation—to determine the appropriate locations for development marked a distinct departure from planning based on promoting economic growth. McHarg tested his theory in practice, most notably in three projects in the USA: The Metropolitan Open Space study of greater Philadelphia, The Plan for the Valleys in Baltimore County, Maryland, and The Woodlands, a new town outside of Houston, Texas. New challenges to regional ecological planning have arisen in the past 30 years: population growth, infrastructure needs, climate change, and social equity and environmental justice. McHarg’s emphasis on the integration of nature and the built environment is still valid, especially in urban/suburban areas, where the use of green infrastructure has gained popularity. McHarg advocated some separation of rural areas from urban/suburban areas to protect farmland and curb sprawl. But more separation is now necessary given America’s much larger and dispersed metropolitan populations. Also, greater emphasis is needed on social equity, environmental justice, and the sustainability of the built environment to provide more affordable housing and to produce more resilient, healthy, walkable, and mixed-use cities and suburbs that rely on mass transit to reduce greenhouse gas emissions.