The goal is an appreciation and recognition of the widespread and over-arching environmental, economic, and social benefits associated with tree cover and a thoughtful prioritization of trees relative to other programs from a funding perspective based on an understanding of the benefits provided by trees.
Trees must survive and grow large to become functional. Survival means more than simply living past the nursery guarantee period, as most planting specifications provide for, prior to this happening any real benefits are not realized and must be classified only as potential benefits. While caring for trees to ensure their survival and maximize growth and longevity involves additional costs, these costs are outweighed by the services provided.
At a minimum, mature trees require 1000 cubic feet of soil which costs money. In the U.S. cities routinely spend $15-20,000 for a streetlight, but $500 per tree...this is a foolish paradigm.