Extent and Area of Swidden in Montane Mainland Southeast Asia: Estimation by Multi-Step Thresholds with Landsat-8 OLI Data

Abstract

Information on the distribution, area and extent of swidden agriculture landscape is necessary for implementing the program of Reducing Emissions from Deforestation and Forest Degradation (REDD), biodiversity conservation and local livelihood improvement. To our knowledge, explicit spatial maps and accurate area data on swidden agriculture remain surprisingly lacking. However, this traditional farming practice has been transforming into other profit-driven land use, like tree plantations and permanent cash agriculture. Swidden agriculture is characterized by a rotational and dynamic nature of agroforestry, with land cover changing from natural forests, newly-cleared swiddens to different-aged fallows. The Operational Land Imager (OLI) onboard the Landsat-8 satellite has visible, near-infrared and shortwave infrared bands, which are sensitive to the changes in vegetation cover, land surface moisture content and soil exposure, and therefore, four vegetation indices (VIs) were calculated, including the Normalized Difference Vegetation Index (NDVI), the Normalized Difference Moisture Index (NDMI), the Normalized Burn Ratio (NBR) and the Soil Adjusted Vegetation Index (SAVI). In this study, we developed a multi-step threshold approach that uses a combination of thresholds of four VIs and local elevation range (LER) and applied it to detect and map newly-opened swiddens and different-aged fallows using OLI imagery acquired between 2013 and 2015. The resultant Landsat-derived swidden agriculture maps have high accuracy with an overall accuracy of 86.9% and a Kappa coefficient of 0.864. The results of this study indicated that the Landsat-based multi-step threshold algorithms could potentially be applied to monitor the long-term change pattern of swidden agriculture in montane mainland Southeast Asia since the late 1980s and also in other tropical regions, like insular Southeast Asia, South Asia, Latin America and Central Africa, where swidden agriculture is still common.

Occurrence frequencies and regional variations in Visible Infrared Imaging Radiometer Suite (VIIRS) global active fires

“…On the basis of previous literature (Li et al, ; Ziegler et al, ) and our field investigations between 2013 and 2019, the burning of sun‐ and air‐dried vegetation of swidden agriculture from February to April during the dry season is widely distributed in MSEA and causes substantial existence of active fires. Thus, we therefore believe that active fires in MSEA are significantly related with traditional slash‐and‐burn practices during the dry season, especially in March and April (Li & Feng, ).…”

“…Our hourly statistical results for the distribution of occurrence frequency of active fires in MSEA were in accordance with the fact that the swiddening practice has been comparatively concentrated between 12:30 and 14:30 ZT during March and April (Müller et al, ). Not coincidentally, some earlier research has shown that active fires in MSEA are usually caused by the swidden‐related burning in the uplands and the burning of agriculture residues in the plain area (Li & Feng, ; Liao et al, ; Shi & Yamaguchi, ; Vadrevu & Justice, ). As a result, this important conclusion comprehensively and robustly validates again the fact that the majority of active fires in MSEA are triggered by swidden agriculture of local farmers (Li, Feng, Xiao, et al, ).…”

Operationalizing a land systems classification for Laos

“…forest cover, there are hardly any spatially explicit datasets covering wide areas that could serve to independently assess the functions, uses and other socio-economic dimensions implicit to the characteristic management type of a landscape. Despite these constraints, we provide alternatives to evaluate the land systems classification of this study by discussing the uncertainties of the input data, the impacts of spatial resolution and compare the classification result to a national mapping of mosaics by Messerli et al 2009 and to remote sensing studies on shifting cultivation by Hurni et al, (2012) and Li & Feng (2016). Finally, we zoom in on two areas to see in how far the classification matches with examples of case study research on shifting cultivation and the agrarian transition.…”

Growth-Ring Analysis of Diploknema butyracea Is a Potential Tool for Revealing Indigenous Land Use History in the Lower Himalayan Foothills of Nepal

“…Land use or fire history assessments can be obtained from archived aerial photographs, satellite images or official records [7][8][9][10]. The slash-and-burn farming shows a specific pattern of regular fire cycles (starting with slashing and followed with ground fire), which is different from the natural forest fires [11].…”