Public trees are more than a luxury, they are valuable elements of urban infrastructure like curbs, sidewalks, water mains, fire hydrants, utility poles, sewer pipes, and so on. The services provided by green infrastructure include measurable improvements in air and water quality, diminished urban heat loads, stormwater detention, public health benefits, and more.
Since “green” infrastructure grows, the benefits derived from the initial investment increase over time, delivering more services with each year that passes (to a point). On the other hand, “grey” infrastructure delivers maximum performance while new and deteriorates with age.
All infrastructure requires maintenance. Because green infrastructure gains value over time, there’s a return on investment. This is not seen as cash to spend elsewhere in the City budget, but it’s an offset of the need to spend additional funds to achieve the same goal. Ex: Trees that provide “shade over pavement” not only moderate the urban heat island effect, but also detain significant rainfall on leaves, branches, and trunk, reducing the peaks in runoff flow that hit storm sewers and, thus, offsetting funds otherwise required to install and maintain larger storm water handling systems.