Deforestation assessment in sub-tropical countries: setting definitions and sampling designs for the national cartography in Mexico
ISBN 978-85-88783-11-9
Authors
1Couturier, S.; 2Martinez, R.; 3Vela, M.
1GEOGRAPHY INSTITUTE, UNAM Email: andres@igg.unam.mx
2GEOGRAPHY INSTITUTE, UNAM Email: rocmargon@gmail.com
3GEOGRAPHY INSTITUTE, UNAM Email: marie.vela14@gmail.com
Abstract
In the perspective of sustainable forest management worldwide, many environmental agencies of subtropical countries still struggle to meet requirements of internationally agreed Monitoring, Reporting and Verification (MRV) schemes. Some methodological features of the national cartographic production systems are very relevant to the future fulfillment of these requirements. In Mexico, environmental-related national agencies have employed novel strategies in the last three years to map and report forest cover and forest cover change from satellite imagery. However, features such as a rigorous accuracy assessment scheme and explicit forest change processes matching internationally recommended definitions are still lacking and as a consequence, much doubt remains about the robustness or comparability in time of the published deforestation rates. This research proposes a national-level deforestation assessment framework, adapted to typical materials and cartography in sub-tropical countries, and applies one stage of this framework for the measurement of the deforestation in accordance with the Food and Agriculture Organization’s (FAO) definition of forest, in the case of a highly bio-diverse area in Southeast Mexico (the edge of a National Biosphere Reserve Montes Azules), currently experiencing high deforestation rates. This framework comprises two features, suitable to the Reduction of Emissions by Deforestation and Degradation (REDD) schemes. The first feature consists in considering a set of three definitions of forest cover change based on the FAO definitions of forests as well as Mexican standards on forest cover definitions. This set of forest cover change definitions permits different levels of deforestation assessment (‘FAO deforestation’ which would reflect total deforestation and only ‘extensive deforestation’) and considers the need for reporting change of a diversity of vegetation types in Mexico. Accordingly, remote sensors with low or high discrimination capacity are suited to different definitions of deforestation/ degradation. The second feature, derived from recent theoretical advances made by the geo-science community, consists in a sampling design that efficiently controls the spatial distribution of samples for all classes, including non-change classes. We explore the application of the entire framework to various national cartographic products (e.g. INEGI maps, the global Landsat-based forest loss map of Hansen et al., 2013) in Mexico. We recommend the method presented here be applied to the national level for the comprehensive accuracy assessment of vegetation cover annual maps of SEMARNAT (the environmental agency in Mexico). This method would ensure very reasonable costs and would contribute to solve the polemical discussions on the reliability of deforestation rates and land use change rates in Mexico. Finally, we specify in which sense the work presented here contributes to set grounds for the quantitative accuracy assessment of global forest cover change cartography.
Keywords
Degradation; Accuracy; Global Warming