Monitoring and characterization of areas submitted to logging in amazonia by change-detection techniques / Monitoramento e caracterização de áreas submetidas à exploração florestal na amazônia por técnicas de detecção de mudanças

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

Selective logging has been affecting extensive areas of primary forests in Amazonia. This activity, when practiced in a predatory way, causes severe environmental impacts such as erosion and soil compaction, increased carbon emissions, increased forest-fire susceptibility and increased risk of local species extinction. Monitoring logging activity is fundamental to establishing action plans and strategies to promote sustainable use of forest resources. However, detection and monitoring of selective logging from satellite imagery is difficult because of the subtle disturbances caused by the partial reduction of forest canopy cover during selective tree harvesting. The main purpose of this study was to develop methodological procedures using change-detection techniques to map, monitor and quantify selectively logged areas in transitional tropical forests in the area of Cláudia and neighborhood, in northern Mato Grosso, using multitemporal data from the ETM and TM Landsat optical sensors. For this, techniques were used such as subtraction of NDVI images, rotation controlled by the axis of no change (RCANC) and change vector analysis (CVA). Additionally, a forest inventory was carried out for the purpose of characterizing the structural and physiognomic changes in forests logged selectively at different intensity levels. The best thematic classification of selective logging areas was obtained using the CVA technique (with the support of the region growth classifier method) followed by application of the RCANC technique. However, the CVA technique required more human intervention during the classification process. Later, the CVA technique was adapted to map areas affected by forest fires. The maps of logged areas obtained using the CVA technique were stored in a GIS with the objective of monitoring land-cover and land-use changes in areas subjected to logging (in the 2001-2003 period) and in forests affected by fire (in the 1999-2003 period). It was found, based on supplementary information obtained from a historical databank for the 1989-2003 period, that the forests affected by logging represented more than half (51%) of the total area classified as forest, and that with annual rates of logging were greater than the rates of deforestation over the 2001-2003 period. However, the logged forests contributed only 17% to the deforestation total up to 2003. This fact demonstrates the important role of logging in the partial conservation of forest cover. Nevertheless, predatory logging (or forest mining) associated with the occurrence of forest fires and can result in a high level of forest degradation, jeopardizing the sustainability of this activity in the region.

ASSUNTO(S)

monitoramento ambiental sensoriamento remoto exploração forestal environmental monitoring detecção de mudanças amazônia forest management amazon region (south america) change detection rain forest floresta tropical remote sensing

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