How Cities are Using Nature to Cut Pollution
Gray infrastructure is the system of pipes and ditches that channel storm water. Green infrastructure is the harnessing of the natural processes of trees and other vegetation — so-called ecosystem services — to carry out the functions of the built systems. Green infrastructure often intercepts the water before it can run into streets and become polluted and stores the water for gradual release through percolation or evapotranspiration. Trees also clean dirty water through natural filtering functions.
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