ENERGY ANDMATERIALFLOWTHROUGH THEURBANECOSYSTEM

Abstract

Key Words megacity biogeochemistry, city succession, industrial metabolism, air pollution, system simulations s Abstract This paper reviews the available data and models on energy and material flows through the world's 25 largest cities. Throughput is categorized as stored, transformed, or passive for the major flow modes. The aggregate, fuel, food, water, and air cycles are all examined. Emphasis is placed on atmospheric pathways because the data are abundant. Relevant models of urban energy and material flows, demography, and atmospheric chemistry are discussed. Earth system-level loops from cities to neighboring ecosystems are identified. Megacities are somewhat independent of their immediate environment for food, fuel, and aggregate inputs, but all are constrained by their regional environment for supplying water and absorbing wastes. We elaborate on analogies with biological metabolism and ecosystem succession as useful conceptual frameworks for addressing urban ecological problems. We conclude that whereas data are numerous for some individual cities, cross-cutting compilations are lacking in biogeochemical analysis and modeling. Synthesis of the existing information will be a crucial first step. Cross-cutting field research and integrated, multidisciplinary simulations will be necessary.

Megacities and Atmospheric Pollution

“…27a PM is often reported as mass concentration in the total suspended particulates (TSP), PM 10 , and PM 2.5 (particles with aerodynamic diameters of less than ϳ40, 10, and 2.5 m, respectively). 27,28 As shown in Table 2, the highest TSP and SO 2 levels appear mostly in Asian cities. These data are limited to cities that measure and report pollutant concentrations.…”

“…102,109 Regional Climate Change Emissions from megacities may also play a role in regional climate impacts. High levels of GHG associated with major cities 27 have a direct impact on IR radiative forcing globally. 110 Furthermore, the powerful but shorter-lived tropospheric O 3 will have a more pronounced regional effect.…”

“…28,117 However, to date, relatively few measurements have been carried out on the polluted outflow from megacities in tropical and subtropical latitudes. Given the high growth rates and rapid industrialization and motorization of these megacities of the developing world, 27 it is likely that regional and even intercontinental transport of pollutants at low latitudes will grow rapidly, posing an even greater challenge.…”

Household analysis identifies water-related energy efficiency opportunities

“…Wolman (1965) identified that water is by far the dominant material flow which passes through cities. Drawing on Wolman's work, Decker et al (2000), suggested that water should be a priority in understanding the metabolism of cities.…”

Greenhouse Gas Emissions from Global Cities

“…Data for some components are available, e.g., for urban transportation (8) or electricity (7). Reviews by Decker et al (9) and Kennedy et al (10) found a paucity of data on overall urban energy consumption. The first challenge of our work in comparing GHG emissions between cities was to establish consistent data on energy use by cities.…”