Urban green space : the effect on climate and the energy implications

Research in several fields outside urban planning indicates increasing occurrences of urban climate anomalies, often in undesirable directions, related to the artificial urban physical environment. A review of published research in urban forestry, geography, climatology, meteorology, landscape architecture and planning was conducted to describe the land use/green space/urban climate interfaces and the variables and magnitude of climate change, and to evaluate the need for and the ways of incorporating the information in urban planning.

The most important variables are the size and density of the development, its surface geometry or shape and materials, and the pollutants and man-made heat generated by these land uses. A dense urban area can exhibit an annual average temperature increase of as much as 6-10°C over short periods, a 5-10% increase in precipitation, and a 15-20% decrease in total incoming solar energy. Urban green space helps not only to moderate such extremes but also to prevent the formation of such anomalies as the urban heat island.

While this climate/land use interface can be most effectively addressed in the design of new towns and large scale developments, there are significant opportunities for urban planners to moderate the urban climate extremes through regulatory, design review and incentive devices applied to redevelopment, infilling, and (quasi)public open space systems. Although there are still problems in accurately predicting the climate changes associated with any given land use, enough parameters are known to begin integrating climate considerations with other urban scale land use planning and implementation strategies.