i-Tree is a collection of software programs for urban forestry that anyone can use. It was designed and developed by the USDA Forest Service to place a value on urban forest ecosystem services such as pollution removal, carbon storage, avoided carbon emissions, and avoided storm water runoff. I-Tree provides baseline data so that the growth of trees can be followed over time, and is used for planning purposes. Reports are based on tree inventories of species, DBH (diameter at breast height) and tree height. I-Tree is peer-reviewed and has a process of ongoing collaboration to improve it.