It’s not easy to price a tree, but a group of researchers from the U.S. Forest Service and U.C. Davis have tried to do exactly that.

Working with a dataset of about 900,000 trees that line California’s public streets, the group sought to place a dollar value on the services those trees perform, which include “energy savings, carbon storage, air pollutant uptake, and rainfall interception.”

All told, the researchers estimate the trees contribute about $1 billion annually — nearly $111 per tree for each of the state’s 9.1 million street trees.