Abstract
Due to the fast deforestation rates in the tropics, multiple international efforts have been launched to reduce deforestation and develop consistent methodologies to assess forest extension and change. Since 2010 Colombia implemented the Mainstream Sustainable Cattle Ranching project with the participation of small farmers in a payment for environmental services (PES) scheme where zero deforestation agreements are signed. To assess the fulfillment of such agreements at farm level, ALOS-1 and ALOS-2 PALSAR fine beam dual imagery for years 2010 and 2016 was processed with ad-hoc routines to estimate stable forest, deforestation, and stable nonforest extension for 2615 participant farms in five heterogeneous regions of Colombia. Landsat VNIR imagery was integrated in the processing chain to reduce classification uncertainties due to radar limitations. Farms associated with Meta Foothills regions showed zero deforestation during the period analyzed (2010–2016), while other regions showed low deforestation rates with the exception of the Cesar River Valley (75 ha). Results, suggests that topography and dry weather conditions have an effect on radar-based mapping accuracy, i.e., deforestation and forest classes showed lower user accuracy values on mountainous and dry regions revealing overestimations in these environments. Nevertheless, overall ALOS Phased Array L-band SAR (PALSAR) data provided overall accurate, relevant, and consistent information for forest change analysis for local zero deforestation agreements assessment. Improvements to preprocessing routines and integration of high dense radar time series should be further investigated to reduce classification errors from complex topography conditions.
Highlights
About 44% of global forests are concentrated in the tropics (1,770,156 thousand ha in 2015 [1]), and is where the vast majority of forest loss occurs, with reported rates of loss of 6.4 M ha year−1 between 2010 and 2015 [1]
The Kyoto and Carbon Initiative has contributed significantly to the development and application of methodologies for forest monitoring in Colombia based on Advanced Land Observing Satellites (ALOS) Phased Array L-band Synthetic Aperture Radar (SAR) (PALSAR) products, allowing us to investigate their application for forest monitoring and deforestation at the local scale; complementing national efforts to quantify forest extent and forest change
The present work highlighted some of the operational issues to be considered in the implementation and replicate of SAR-based systems for forest monitoring
Summary
About 44% of global forests are concentrated in the tropics (1,770,156 thousand ha in 2015 [1]), and is where the vast majority of forest loss occurs, with reported rates of loss of 6.4 M ha year−1 between 2010 and 2015 [1]. In Colombia, approximately one third of forest cover has been cleared since the year 1700, as a result of multiple, heterogeneous historical processes [2]. At the beginning of the 20th century the agricultural footprint rapidly increased due to population growth; cattle ranching played an especially important role in landscape change dynamics within the country [2]. As a response to the rapid advance of global forest loss and degradation, the UN Framework Convention on Climate Change (UNFCCC) launched the Reducing Emissions from Deforestation and Forest Degradation program (REDD+). The general aim of REDD+ is to contribute to the mitigation of climate change by reducing greenhouse gas (GHG) emissions by decreasing and reversing forest loss and degradation, and by increasing the removal of GHGs through conservation and the expansion of forests [11]. In 2008, the national government of Colombia in collaboration with UN launched the UN-REDD program in Colombia; since multiple collaboration initiatives, promoted especially by NGOs and multilateral organizations, implemented environmental programs based on the REDD+ approach that presented the Readiness Preparation Proposal for Colombia in 2013
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