A review of methods to measure and monitor historical carbon emissions from forest degradation

Disturbances that lead to forest degradation have been estimated to affect roughly 100 million hectares (ha) of forest globally per year (FAO, 2006, in Nabuurs et al., 2007). With respect to mitigation of climate change, forest degradation refers to a loss of carbon stock within forests that remain forests (IPCC, 2003a; UNFCCC, 2008). Degradation, therefore, implies that measured forest variables, such as canopy cover, remain above the threshold " ~ from deforestation, which is commonly associated with a land-use change. In 2005, the eleventh session of the Conference of Parties (COP-11) to the United Nations Framework Convention on Climate Change (UNFCCC) highlighted the role of reducing deforestation and forest degradation as tools to mitigate climate change (Reducing Emissions from Deforestation and Forest Degradation – REDD). The Conference reinforced Article 2 of the Kyoto Protocol regarding the protection and enhancement of sinks and reservoirs of greenhouse gases not controlled by the Montreal Protocol. Developing country Par ties to UNFCCC have been encouraged to take certain guidance into account when engaging in REDD and REDD+ activities (UNFCCC, 2009a), in particular, those related to establishing national forest monitoring systems. These systems need to use an appropriate combination of remote sensing and ground-based approaches to forest carbon inventory to estimate anthropogenic emissions of greenhouse gas by sources, removals by sinks, forest carbon stocks and forest area changes. All estimates should be transparent, consistent and as accurate as possible, and uncertainties should be reduced, as far as national capabilities and capacities permit. Measuring forest degradation and related forest carbon stock changes is more complicated and more costly than measuring deforestation. Countries can measure current rates of degradation through field data and/or remote sensing data; a combination of the two types of data provides the strongest estimates. However, developing countries frequently lack consistent historical field data. Therefore, in assessing historical degradation, they are forced to rely strongly on remote sensing approaches mixed with current field assessments of carbon stock changes. This article aims to support developing countries in the implementation of REDD+ activities by providing an overview and review of methods to measure and monitor carbon emissions from forest degradation. It focuses on historical periods in order to provide insight into the historical reference for degradation under REDD+ activities (UNFCCC, 2009b).