Multi-temporal analysis of Landsat images for deforestation assessment in the Bosawas Biosphere Reserve

According to the latest forest assessment from the Food and Agriculture Organization of the United Nations in 2015, about 129 million hectares of forest have been loss in the past 25 years. Illegal settlements, illicit logging, and slash-and-burn farming practices are the main drivers of deforestation, especially in developing countries. The objective of this study is to assess and analyze the deforestation process in the nucleus zone of the Bosawas Biosphere Reserve, in Nicaragua, Central America, by means of remote sensing image classification and interpretation. As found out by the German International Cooperation in 2012, during the period 1987-2010 the area of loss forest corresponds to 13.6% of the total core zone. For this study, Landsat images from 2011 and 2015 were classified using both object-based and pixel-based classification approaches. Afterwards, the accuracy assessment was conducted to evaluate the performance of both methods. Finally, the net loss of total forest area was calculated by comparing the forest cover of both periods. The results of the accuracy assessment for the image of 2012 yields a Kappa coefficient of 0.89, and overall accuracy of 87% for both methods. For the image of 2015, the overall accuracy is 95%, with a Kappa value of 0.93. For the latter case, a significant improvement with respect to the pixel based method generates a Kappa of 0.84 and overall accuracy of 87%. Examination of the 2011 land cover reveals that around 6206.77 km² corresponded to broadleaf forest cover. This represents 86.5% of the total area analyzed. By 2015 the forest cover diminished to 5825.14 km², with a net forest loss equivalent to 5% of the study area. The results indicate that deforestation is an ongoing issue in the area, and that the deforestation rate has increased in the last decade.