Atmospheric Carbon Dioxide Reduction by Sacramento's Urban Forest

Sacramento County's 6 million trees store 8 million tons of CO2 (31 t/ha), and annually sequester 238,000 t (0.92 t/ha). Air-conditioning (157 GWh) and space-heating (145 TJ) savings from the urban forest further reduce emissions by 75,600 t of CO2 annually (0.29 t/ha). These avoided emissions are only 32% of the amount sequestered, due to a clean, hydroelectric energy supply. Annual CO,, release associated with tree maintenance is estimated at 9,400 t (0.04 t/ha), or 3% of the amount sequestered and avoided. In net, the urban forest removes approximately 304,000 t (1.2 t/ha) each year, with an implied value of US$3.3 million ($0.55/tree). Carbon dioxide reduction by Sacramento's urban forest offsets the total amount of COa emitted as a byproduct of human consumption by 1.8%. Most benefits accrue on residential lands in the city and suburban sectors, where rates of storage and sequestration are about one-half those reported for U.S. forests. Guidelines for managing urban forests to reduce atmospheric CO2 are presented.