The researchers evaluated more than 117,000 trees the Indianapolis Parks and Recreation Forestry Section manages and found every $1 spent brought a $6.09 return.

Scientists involved in the study found Indianapolis trees annually intercept 318.9 million gallons of rainfall, which they estimate to be worth $1.98 million or $17 per tree per year.

The trees also annually cut electricity use by more than 6,447 megawatt hours, worth $432,000. They reduce natural gas use by more than 150,000 therms, bringing annual benefits worth $165,000 or $5 per tree.

Each tree annually removes 1.5 pounds of air pollutants, valued at $2 per tree or $212,000, according to the scientists. They also estimated the trees increased property values and provided less tangible benefits worth $2.9 million or on average $24 per tree.

Scientists analyzed 2005 expenditures and found Indianapolis spends about $940,000 in a typical year planting new trees and maintaining existing ones. The biggest single cost and more than half the annual budget was for tree removal at $491,000, followed by pruning at $122,000. Overall, the annual return for the planting, care and management of the 117,525 trees in the study reached nearly $5.7 million.