Chapter 5. Forests and Climate
Overview of Chapter 5: Forest Contribution to Global Carbon Cycles
California’s forests are an important contributor to global carbon cycles and act to help regulate climatic changes. Scientists generally have agreed that the earth’s climate is changing. Most believe that this is at least partly due to human activities that have altered the chemical composition of the atmosphere through the buildup of greenhouse gases—primarily carbon dioxide, methane, and nitrous oxide. These gases trap heat. Although uncertainty exists about exactly how earth’s climate responds to these gases, global temperatures are rising. This is shown in the graph that indicates rise in the departure from long-term mean annual temperature.
Global temperature change, 1880-2000
Forests play an important role in the earth's carbon cycle. On one hand, the loss of forests on a global scale to other uses (deforestation) is responsible for up to one-third of carbon emissions to the atmosphere, and ranks second only to the burning of fossil fuels as a source of CO2 emissions. On the other hand, forests serve as a huge carbon sink: they capture CO2 from the atmosphere through photosynthesis and store it as carbon in wood and other carbon-based compounds in soil, in understory plants, and in the litter on the forest floor. Large amounts of additional carbon could be stored in U.S. forests, including those in California.
Over the last decade, international discussions have focused on how to address global warming by reducing the increases in greenhouse gases. Two general approaches have been taken to forests: (1) reduction of the harvest and burning of extensive forest acreages, and (2) development of approaches to grow and hold carbon (called sequestration) in trees.
Montreal process indicators for forest contribution to global carbon cycles
Montreal Process Criterion 5 deals with maintenance of forest contribution to global carbon cycles. Indicator 26 focuses on the total forest ecosystem biomass and carbon pool. This allows measurement of how forests over time add and hold carbon. Indicator 27 relates to the contribution to the total global carbon budget, including absorption and release of carbon above and below ground. Indicator 28 addresses contribution of forest products to the global carbon budget.
Indicator 67 under Montreal Criterion 7 (Forest Sustainability) also deals with the ability to predict impacts on forests of possible climate change. For continuity this indicator is also discussed in this section.
Work on the forest contribution to global climate change and carbon sequestration started in the early 1990s and has accelerated rapidly in recent years. A number of agencies have been involved in these efforts such as the California Energy Commission, the U.S. Environmental Protection Agency, and the USDA Forest Service.
Assessment sections summarizing Chapter 5: Overview of Forest Contribution to Global Carbon Cycles
In this Assessment, FRAP will address the criterion of Maintaining Forest Contribution to Global Carbon Cycles with a on-line technical report that reviews California’s forests and rangelands and their role in carbon storage. This report summarizes information for the four indicators related to this topic (Montreal Process indicators 26, 27, 28, and 67). The section is linked in a separate Adobe Acrobat pdf file below:
U.S. Forest Service. 1997. Report of the United States on the Criteria and Indicators for the Sustainable Management of Temperate and Boreal Forests. Web site accessed November 4, 2002.