![[logo] US EPA](http://www.epa.gov/epafiles/images/logo_epaseal.gif){kind=logo}
Addressing Permanence of Projects
Common Definition:
Permanence refers to the potential for carbon sequestered in agriculture and forestry to be partially or completely reversible. The carbon that accumulates in vegetation and soils can be released back to the atmosphere either through natural events (e.g., forest fires) or human activities (e.g., harvesting of trees, change in tillage practice for croplands).
Importance:
The permanence of carbon benefits is characteristic of agricultural and forestry projects, due to the dynamic biological processes of the carbon cycle involved. Addressing permanence can help contribute to the environmental credibility of agricultural and forestry sequestration projects. In particular, the risk of losing carbon sequestration benefits may need to be addressed over two kinds of timeframes: 1) during the project timeframe; and 2) after the project timeframe ends.
Status:
There is currently no standard method for addressing the permanence of sequestration projects. Proposed ideas to date include the use of insurance mechanisms, project diversification to mitigate the risk of losing benefits, the issuance of temporary credits, and discounting credits. References to analyses that examine the use of these options to address permanence are provided below.
Permanence and Saturation:
Closely related to the permanence issue is the fact that carbon sequestration eventually saturates. As trees mature, for example, their growth and thus carbon sequestration rates slow and eventually level off. If left undisturbed, carbon saturation in trees may not occur until at least 80 years in the U.S. For agricultural soils, carbon sequestration rates may saturate after about 15-30 years (see the Practices section of this Web site for more information on typical saturation periods). The implication for projects is that, even after carbon saturation has been reached, activities may need to be maintained to prevent the accumulated carbon from being released back to the atmosphere (e.g., mature trees may need to be protected, or conservation tillage practices may need to continue).