Assessing the Geoecological Functions of the Green Infrastructure in Cities of Canada

摘要

An assessment is made of the geoecological functions of the green infrastructure for the cities of Canada by using landscape-basin approach at three spatial levels: regional, intra-urban and local. The study revealed regional and functional differences in the green infrastructure of Vancouver, Toronto and Ottawa, and determined the quantitative relationships between territories that have biospheric, recreational, foodproducing and environment-regulation functions. It is shown that the general urban (average according to the spatial scale) level develops many important attributes of configuration of the green infrastructure which come to be intimately linked to the history and modern tendencies of urban development. It is established that for the intra-urban level (Toronto), the large-area elements have the functions of a stabilization of the environment and sustainment of biodiversity, whereas area-limited fragments most often serve as recreational places of the public nearest access. We calculated the proportion of the urban area corresponding to different (according to the functions of runoff formation) types of catchment units; almost one-third of the area is represented by catchment units with no permanent streams or with a transformed drainage system. It is found that the highest percentage of forest land corresponds to the downstream portions of river basins and to areas along valleys, whereas these indicators are much lower in the upstream regions and near drainage divides. It is established that there is almost no correlation between the size of the runoff cell and its percentage of forest land and the degree of development.