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Individual Highlight

Trees in Los Angeles: Carbon Dioxide Sink or Source

Photo of Two members from the Los Angeles Conservation Corps plant a tree. The Los Angeles tree programknown as Two members from the Los Angeles Conservation Corps plant a tree. The Los Angeles tree programknown as "City Plants" stressed creating jobs, particularly for underserved youth and young adults in Los Angeles. Through its partnership with the Los Angeles Conservation Corps, 208 young people earned their high school diplomas while working on the program. Elizabeth Skrzat, City PlantsSnapshot : Tree planting is considered to be among the most effective approaches to cooling urban environments and mitigating carbon dioxide emissions. The Los Angeles tree program known as "City Plants" is one of several mayoral tree planting initiatives launched in the largest U.S. cities. Altogether, the largest cities have pledged to plant nearly 20 million trees, in most cases for climate protection. The assumption behind these tree planting initiatives is that trees are a net long-term carbon dioxide sink, but because there has never been a full accounting of carbon dioxide emissions for a tree planting initiative, some people question their effectiveness.

Principal Investigators(s) :
McPherson, E. Gregory 
Research Location : Los Angeles, CA (conducted out of Davis, California)
Research Station : Pacific Southwest Research Station (PSW)
Year : 2014
Highlight ID : 688

Summary

Carbon dioxide emissions and reductions from storage and avoided emissions from energy savings were simulated for 91,786 trees planted from 2006 to 2010, of which 30,813 (33.6 percent) were estimated to survive. Early results suggest that these plantings are achieving success in terms of survival, growth, and performance. The Los Angeles tree program was estimated to release 17,048 tons and 66,360 tons of fossil and biogenic carbon dioxide respectively over the 40-year period. The total amount emitted (83,408 tons) was slightly more than the -77,942 tons carbon dioxide that trees were projected to store. The largest sources of carbon dioxide emissions were mulch decomposition (65.1percent), wood combustion (14.5 percent) and irrigation water (9.7 percent). However, the Los Angeles tree program will be a carbon dioxide sink if 40-year projections about the avoided fossil fuel carbon dioxide emissions from energy savings (-101,679 tons) and biopower (-1,939 tons) are realized. The research findings suggest that this tree planting initiative, and possibly others, can be net carbon dioxide sinks, especially if trees are strategically located to reduce energy consumed for air conditioning and heating. Forest Service scientists also found that there is ample opportunity to further reduce emissions. Examples include selecting drought tolerant trees and utilizing wood for wood products or to generate electricity instead of for producing mulch.

Forest Service Partners

External Partners

 
  • City Plants
  • LA Bureau of Street Services
  • LA Recreation and Parks Department
  • Los Angeles Conservation Corp.
  • TreePeople
  • UC Davis, Department of Civil and Environmental Engineering