Using tree inventory data from 49 cities analyzed in i-Tree, a computerized tree inventory and management suite, Forest Service researchers were able to create a composite picture of not only the number of California's street trees, but also their species, size, location and associated benefits. An estimated 9.1 million trees, providing ecological services valued at $1 billion, are lining California's streets and boulevards, with room for another 16 million trees. While numbers have increased from 5.9 million in 1988, tree density has actually fallen from 105 to 75 trees per mile, nearly a 30 percent drop. From carbon storage ($10.32 million) and removal of air pollutants ($18.15 million) to interception of rainfall ($41.5 million) and energy savings from both heating and cooling ($101.15 million), California's street trees are paying big dividends. They even bolster property values and home sale prices to the tune of $838.9 million. Researchers concluded that for every $1 invested in street trees, the trees returned $5.82 in benefits.