Parks in stream valleys or urban wetlands absorb storm water much more cheaply than in artificial systems. Dwyer, John F. 1993. The Economic Contribution of Trees to Urban Communities. Trees have been found to be effective for conserving energy used for residential heating and cooling. The maximum potential annual savings from energy-conserving landscapes around a typical residence ranged from 13 percent in Madison up to 38 percent in Miami.
Trees reduce air pollution through absorption of gases and interception of particulates.
They also reduce temperatures which reduce emissions from a number of sources. To the extent that trees improve air quality, there is potential for even greater savings through reduced health care, less material damage and cleanup and improved visibility. Reduced runoff due to rainfall interception can also reduce stormwater treatment costs in many communities, reduce flooding, and improve water quality.