Sources of Greenhouse Gas Emissions

Land Use, Land-Use Change and Forestry Sector Emissions

Plants absorb carbon dioxide (CO₂) from the atmosphere as they grow, and they store some of the carbon throughout their lifetime. Soils can also store CO₂, depending on how the soil is managed. This storage of carbon in plants and soils is called biological carbon sequestration. Because biological sequestration takes CO₂ out of the atmosphere, it is also called a greenhouse gas "sink."

Emissions or sequestration of CO₂ can occur as land uses change. For example, CO₂ is exchanged between the atmosphere and the plants and soils on land as former cropland is converted into grassland, as new areas are cultivated and become cropland, or as forests grow. In addition, using biological feedstocks (such as energy crops or wood) for purposes such as electricity generation, input to processes that create liquid fuels, or building materials can lead to emissions or sequestration.

In the United States overall, since 1990 land use, land-use change, and forestry activities have resulted in more removal of CO₂ from the atmosphere than emissions. Because of this, the Land Use, Land-Use Change, and Forestry (LULUCF) sector in the United States is considered a net sink, rather than a source, of CO₂ over this period. In many areas of the world, the opposite is true: In countries where large areas of forest land are cleared, often for agricultural purposes or for settlements, the LULUCF sector can be a net source of greenhouse gas emissions.

More national-level information about land use, land-use change, and forestry is available from the Land Use, Land-Use Change, and Forestry chapter in the Inventory of U.S. Greenhouse Gas Emissions and Sinks .
See EPA's Global Greenhouse Gas emissions page for more information about global GHG emissions from land use and forestry activities.
For more information about global emissions from land use and forestry activities, see the Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change.

Emissions and Trends

In 2011, the CO₂ removed from the atmosphere from the LULUCF sector offset about 14% of total U.S. greenhouse gas emissions. Forests (including vegetation, soils, and harvested wood) accounted for approximately 92% of this 2011 LULUCF CO₂ flux.

The total carbon sequestration by the LULUCF sector has increased by about 14% since 1990, largely as a result of changes in the land area of forests and improved forest management.

To learn about projected greenhouse gas sinks from the LULUCF sector to 2020, visit the U.S. Climate Action Report 2010 (PDF). (193 pp, 3.1 MB)

Carbon Emissions from U.S. Land Use, Land-Use Change, and Forestry*

Line graph of carbon emissions from land use, land use change, and forestry for 1990 to 2009. The greenhouse gas emissions started around negative 800 million metric tons of carbon dioxide equivalent and rose to a peak of about negative 550 million around 1999. From 2000 to about 2003 the line drops quickly to about negative 1,050 million and it only rises slowly until 2009 where it ends around negative 1,000 million metric tons of carbon dioxide equivalents.

*Note: The LULUCF sector is a net "sink" of emissions in the United States (e.g., more greenhouse gas emissions are sequestered than emitted from land use activities), so net greenhouse gas emissions from LULUCF are negative.

All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2011.

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Reducing Emissions and Enhancing Sinks from Land Use, Land-Use Change, and Forestry

In the LULUCF sector, opportunities exist to reduce emissions and increase the potential to sequester carbon from the atmosphere by enhancing sinks. The table shown below provides some examples of opportunities for both reducing emissions and enhancing sinks. For a more comprehensive list, see Chapter 8 and Chapter 9 of the Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change..

Examples of Reduction Opportunities in the LULUCF Sector
Type	How Emissions are Reduced or Sinks are Enhanced Examples	Examples
Change in Uses of Land	Increasing carbon storage by using land differently or maintaining carbon storage by avoiding land degradation.	Encouraging the transformation of cropland to forest. Avoiding the conversion of forest land to settlements.
Changes in Land Management Practices	Improving management practices on existing land-use types.	Reducing soil erosion to minimize losses in soil carbon storage. Planting after natural or human-induced forest disturbances to accelerate vegetation growth and minimize soil carbon losses.