The response of the terrestrial biosphere to urbanization: land cover conversion, climate, and urban pollution

K Trusilova,G Churkina

doi:10.5194/bg-5-1505-2008

Abstract

Abstract. Although urban areas occupy a relatively small fraction of land, they produce major disturbances of the carbon cycle through land use change, climate modification, and atmospheric pollution. In this study we quantify effects of urban areas on the carbon cycle in Europe. Among urbanization-driven environmental changes, which influence carbon sequestration in the terrestrial biosphere, we account for: (1) proportion of land covered by impervious materials, (2) local urban meteorological conditions, (3) urban high CO2 concentrations, and (4) elevated atmospheric nitrogen deposition. We use the terrestrial ecosystem model BIOME-BGC to estimate fluxes of carbon exchange between the biosphere and the atmosphere in response to these urban factors. We analysed four urbanization-driven changes individually, setting up our model in such a way that only one of the four was active at a time. From these model simulations we found that fertilization effects from the elevated CO2 and the atmospheric nitrogen deposition made the strongest positive contributions to the carbon uptake (0.023 Pg C year−1 and 0.039 Pg C year−1, respectively), whereas, the impervious urban land and local urban meteorological conditions resulted in a reduction of carbon uptake (−0.005 Pg C year−1 and −0.007 Pg C year−1, respectively). The synergetic effect of the four urbanization-induced changes was an increase of the carbon sequestration in Europe of 0.058 Pg C year−1.

Highlights

Urban population is growing at a much faster rate than the Earth’s total population (WRI, 1996) and this leads to the growth of urban areas and often to an increase of urban pollution
Among urbanization-driven environmental changes, which influence carbon sequestration in the terrestrial biosphere, we account for: (1) proportion of land covered by impervious materials, (2) local urban meteorological conditions, (3) urban high CO2 concentrations, and (4) elevated atmospheric nitrogen deposition
As urban areas continue to grow potential carbon sink on land is shrinking because vegetated land is replaced by land covered with impervious materials

Summary

Introduction

Urban population is growing at a much faster rate than the Earth’s total population (WRI, 1996) and this leads to the growth of urban areas and often to an increase of urban pollution. In desert and semi-desert regions urbanization leads to an increase in vegetation cover. As urban areas continue to grow potential carbon sink on land is shrinking because vegetated land is replaced by land covered with impervious materials (buildings, roads, parking lots, etc.). Urban areas occupy a small land fraction of about 2–3% of the Earth’s surface (WRI, 1998), they are sources of about 90% of anthropogenic carbon dioxide (CO2) globally. All consequences of urban development mentioned above have a great potential to influence the carbon cycle and to cause irreversible damage to the surrounding land ecosystems

Methods

Results

Conclusion