Urbanised territories as a specific component of the global carbon cycle

Abstract

Although urbanised territories (UT) produce most part of the anthropogenic emissions, we will only consider the following impacts on the Global Carbon Cycle (GCC): a) the additional carbon emissions that result from the conversion of natural, surrounding a city land, caused by urbanisation and b) the change of carbon flows by ''urbanised'' ecosystems, when the atmospheric carbon is ''pumping'' through ''urbanised'' ecosystems into neighboring natural ecosystems along the chain: atmosphere #-># vegetation #-># dead organic matter, i.e. export flow. The main task is to estimate the annual regional dynamics of the total carbon balance in UT with respect to the atmosphere from 1980 till 2050. As a scenario, we use the prognoses of regional urban populations produced by the ''hybrid'' model (multiregional demographic model + UN regional prognoses). All the estimations of carbon flows are based on two models. In the first model (minimal estimates), a regression equation relating the city area and population, is used, as well as an assumption about a random spatial distribution of cities. In the second model (maximal estimates), the so-called #GAMMA#-model is used, based on the assumption that the distribution of populated areas with respect to population density is a #GAMMA#-distribution with a non-random spatial distribution of cities. The urbanised area is sub-divided into ''green'' (parks, etc.), built-up and informal settlements (favelas) areas. The regional and world dynamics of carbon emission and export, and the annual total carbon balance are calculated. Qualitatively, both models give similar results, but there are some quantitative differences. In the first model, the world annual emissions as a result of land conversion will attain a maximum of 205 MtC between ca. 2020-2030. Emissions will then slowly decrease, so that by the year 2050, they will equal ca. 150 MtC. The maximum contributions to world emissions are given by China and the Asia and Pacific regions. In the second model, the world annual emissions increase from 1.12 GtC per year in 1980 up to 1.25 GtC per year in 2005, after which it will begin to decrease, such that by the year 2050, emissions will have decreased to 623 MtC. If we compare the emission maximum, 1.25 GtC per year, with the annual emission caused by the process of deforestation, 1.36 GtC per year in 1980, then we can say that the role of UT is of a comparable magnitude to the role of deforestation. (orig.)Available from TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman