Tree Ordinances have been successful at tree banking and tree planting, but it is rare they prevent the removal of existing trees on lots being developed or redeveloped in desirable urban areas. The reason, the perceived value of the land exceeds the value of the tree.
Trees require their roots, and in poor urban soils those roots can take up large swaths of land, often referred to as the critical root zone. The science dictates that removing more than one-third of the root zone can put trees into drought conditions since there are less absorbing roots to give water to the trees. Trees like us are mostly water, and when you restrict water they often die, although most often that decline can be over five to seven years.
Most large urban trees reside in older residential areas. These trees grow up mostly undisturbed in a front, back, or side yard for fifty years or more. The lots are often less than a quarter of an acre and run from $200-500K. The lot is attractive for development and/or rennovations due to its intown location combined with an existing home that is affordable due to its age and size. To maximize profit, the builder wants to build the most expensive home to fit on the lot. The homeowner doing a renovation wants a larger home. Lets say when the new home is completed it will sell for 800K allowing developer to recover their costs and some profit and the homeowner to gain some value. The problem is that the critical root zone of the existing tree on the lot could take up to 50% of the buildable area. Unless the penalty to remove it exceeds the return on the property, that tree is coming down. In the scenario presented that would require a penalty of around $100K to not make it economically feasible to remove that tree.
As a result of this difficultly, tree ordinances do not usually require saving existing trees or do not give a high enough penalty to protect them but instead encourage replanting and/or tree banking (recompense). In my next blog I will discuss the economics of tree banking and replanting.