Getting started>Why?>Carbon reduction
The role of urban trees in reducing greenhouse gases
Like other forests, urban forests play a role in a reducing the amount of greenhouse gases (GHG) in the atmosphere.
"Trees in cities affect GHG in three main ways:
- As they grow, they remove carbon dioxide and other GHG from the atmosphere and sequester them in their leaves, branches, trunks and roots. When trees die, the carbon is released back into the air through decomposition. Carbon remains stored in portions of trees that are protected from decomposition, [e.g.,] wood used for building.
- By shading buildings in summer and blocking cold winter winds, trees reduce electricity and natural gas use, which reduces the production of GHG at the power plant or home furnace.
- Wood from dead trees can be used to produce energy, create biofuel, and for thermal heat and cooling, replacing fuels that produce more GHG."
Center for Urban Forest Research, Urban Forests and Climate Change: Greenhouse Gas Reporting Protocol
As part of fulfilling its responsibilities under AB32,The Global Warming Solutions Act, in September 2008, the California Air Resources Board approved the Urban Forest Protocols. These protocols were developed by the Center for Urban Forest Research, Pacific Southwest Research Station. The protocols were adopted by the California Climate Action Registry Board in August 2008.
The protocols consist of two interrelated products:
- Urban Forest Program Reporting Protocol - This protocol describes the requirements that must be met for an urban forest project to register carbon reductions with the California Climate Action Registry. To qualify, projects need to represent additions to baseline levels, i.e., above and beyond business as usual. GHG reductions also need to be sustained for at least 100 years and not detract from management of existing trees. Information is also provided on how to calculate and report carbon storage by project trees, as well as emissions associated with their maintenance. The USDA Forest Service Climate Change Resource Center web site also provides a Tree Carbon Calculator that can be used to quantify carbon dioxide sequestration from GHG tree planting projects. The application is currently available as an Excel-based spreadsheet tool available for download. A Web-based version with greater functionality is planned for future release.
- Urban Forest Project Verification Protocol - This protocol is intended for use by approved independent verifiers who audit and verify greenhouse gas (GHG) emission reductions associated with a planned tree planting projects. Verification occurs on an annual basis. GHG project developers, such as urban forest managers, should be familiar with the Verification Protocol because any project they report will need to comply with its requirements.
The protocols are intended to establish a basis for investment in large-scale tree planting and stewardship projects that generate additional, verifiable, and permanent GHG reductions. Because the carbon reductions under this program are registered and follow well-documented reporting and verification protocols, they represent high quality offsets that can be purchased by corporations, utilities, and individuals to offset their emissions or become carbon neutral.