American Forests, the oldest national nonprofit conservation organization in the US, advocates for the protection and expansion of America’s forests. Since 1990, They have planted more than 45 million trees. They restore watersheds to help provide clean drinking water. They replant forests destroyed by human action and by natural disasters. This website contains a number of resources related to the protection of forest but also to assess the health status of urban trees. A specific section is dedicated to the measurement and appraisal of the value of a tree. The four major factors involved in properly assessing the value of a plant are size, species, condition and location. A thorough understanding of each is imperative. This website collect a number of calculators available on line to asses the volume of a tree. These calculators use the species, circumference or diameter, health and location to determine the current environmental and economic benefits your tree is providing, as well as the projected benefits your tree will provide over a set number of years.