Shade trees reduce building energy use and CO2 emissions from power plants.
Urban shade trees offer significant benefits in reducing building air-conditioning demand and improving urban air quality by reducing smog. The savings associated with these benefits vary by climate region and can be up to $200 per tree. The cost of planting trees and maintaining them can vary from $10 to $500 per tree. Tree-planting programs can be designed to have lower costs so that they offer potential savings to communities that plant trees. Our calculations suggest that urban trees play a major role in sequestering CO2 and thereby delay global warming. We estimate that a tree planted in Los Angeles avoids the combustion of 18 kg of carbon annually, even though it sequesters only 4.5-11 kg (as it would if growing in a forest). In this sense, one shade tree in Los Angeles is equivalent to three to five forest trees. In a recent analysis for Baton Rouge, Sacramento, and Salt Lake City, we estimated that planting an average of four shade trees per house (each with a top view cross section of 50 m2) would lead to an annual reduction in carbon emissions from power plants of 16,000, 41,000, and 9000 t, respectively (the per-tree reduction in carbon emissions is about 10-11 kg per year). These reductions only account for the direct reduction in the net cooling- and heating-energy use of buildings. Once the impact of the community cooling is included, these savings are increased by at least 25%.
Akbari
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Heat Island Group, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. h_akbari@lbl.gov
D000389:Air Conditioning / Q000191:economics; D002245:Carbon Dioxide / Q000032:analysis*; D003247:Conservation of Natural Resources; D017046:Cost Savings; D004736:Energy-Generating Resources; D005160:Facility Design and Construction; D006361:Heating / Q000191:economics; D011210:Power Plants; D014197:Trees
D002245:Carbon Dioxide