Reforestation/afforestation has already been incorporated into current international efforts to create carbon "offsets," along with renewable energy and energy efficiency programs, and projects that qualify under the Kyoto Protocol Clean Development Mechanism. However, current implementation of forest-based carbon sequestration is limited to private enterprise engaged in selling carbon-offsets, and to some nations with commitments under the Kyoto protocol. As a geoengineering strategy, reforestation/afforestation would be far more extensively and systematically employed and managed to sustain a larger-scale drawdown - and sustained sequestration of CO2.
Mitigation Option: Very large-scale reforestation of previously cleared land, reclamation of mine land, afforestation of marginal lands, agroforestry, forest preservation, and urban forestry has been proposed . With investment in inventory management and monitoring, development of appropriate technologies and decision support systems, an estimated additional 100-200 Tg C/year of forest carbon sequestration is, for example, achievable within the US. New forestry technologies including improvements in thinning and better utilization of products from thinning, low-impact harvesting, optimizing rotation length, species or genotype selection, and forest biotechnology will be required to achieve significant drawdown .
Feasibility: The success of forestry for CO2 direct capture and sequestration depends on a number of variables: harvesting and soil disturbance rates, future forest productivity, site characteristics, and the local environment. Quantification and verification of sequestered CO2 requires measurement of the exchange of CO2 between forests and the atmosphere - this is by no means trivial, given the number of individual carbon pools present in a forest ecosystem. An added complication is that the stability of forest carbon sequestration is vulnerable to natural disturbances. Stored carbon in forests can be unexpectedly released back to the atmosphere due to, for example, wildfires, and insect infestations.
Estimates of the feasibility of forest management as a mechanism for reducing atmospheric CO2 levels must factor in the climate-induced changes that will occur in forest ecosystems, due to climate warming currently underway  . Warming can be expected to negatively affect forest productivity.
An important cost consideration is the requirement that forest management technologies, along with the necessary resources, must be available in a sustained manner to international carbon managers in order to ensure the success of this strategy at the global scale.
Co-benefits and undesirable consequences: Restored forestlands, and the cultivation of new-forested areas may be beneficial for wildlife and regional ecosystems. However, silviculture on marginal and reclaimed lands implies the need for extensive fertilization and irrigation, with coincident risk of water pollution, nutrient runoff impacts (such as the extensive dead zone in the Gulf of Mexico) and depletion of fresh water supplies.
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