Forest cover is changing in several places of the world because of the severe human interference. The globe has lost 178 million ha of forest since 1990 though the pace of net forest loss significantly slowed between 1990 and 2020 (FAO, 2020). Over the decades 1990–2000, 2000–2010, and 2010–2020, the rate of net forest loss has decreased from 7.8 million ha to 5.2 million ha and finally to 4.7 million hectares per year, respectively (FAO, 2020). In order to understand the dynamic changes of forest cover in different parts of the globe, there is a need for continuous forest monitoring and generating accurate statistics on forest and forest cover change.
Monitoring changes in forest cover has been notably progressed on global, regional, and local scales by the advancement of new imaging sensors and geospatial technologies. Many research efforts have been undertaken using various approaches and data-sets to detect forest cover changes throughout the globe. Hansen & DeFries (2004) utilized Advanced Very High-Resolution Radiometer (AVHRR) data and a supervised algorithm technique to assess the changes in global forest cover. Hansen et al. (2008) integrated Landsat and MODIS data to produce a per-pixel change map of forest cover in the Congo Basin. Using Landsat and IRS LISS III data, Panigrahy et al. (2010) detected changes in forest cover in Western Ghats of Maharashtra by employing a visual interpretation approach.
Spatial changes of Romania’s montane forest cover were mapped using a supervised maximum likelihood classification algorithm to Landsat and Sentinel- 2 images (Mihai et al. 2017). Multi-sensor image data from Landsat 1–8, Sentinel- 1 and 2, CBERS, ASTER, ISS have been utilized to detect changes in Brazilian forest cover (Fortin et al. 2020). Nguyen-Trong & Tran-Xuan (2022) estimated changes of coastal forest cover in Vietnam using Sentinel- 2 images and a convolutional neural networks approach. Machine learning algorithms have recently gained popularity in recent time as a technique for processing and analysing satellite images due to their ability for large amount of data handling and automation procedures. Roberts et al. (2022) generate a Python package that enables the detection of near-real-time change in forest cover in Kenya using Sentinel and Landsat data.
Forests in Bangladesh are also undergoing changes due to extreme human interference like many other tropical countries (i.e. Emch & Peterson, 2006; Zaman & Katoh, 2011; Redowan et al., 2014; Abdullah et al., 2015). Studies related to forest cover change in Bangladesh have primarily focused on the Sundarbans (Islam et al., 1997; Emch & Peterson, 2006; Giri et al., 2007; Hasan et al., 2020; Chowdhury & Hafsa, 2022). However, a few studies have also been done on the forest regions of the south-eastern part (Nath & Acharjee, 2013; Samrat et al., 2022), north-eastern part (Redowan et al., 2014; Masum & Hasan, 2020) and Sal forest located in the central and the north-western part of the country (Zaman & Katoh, 2011; Abdullah et al., 2015). The majority of these studies used Landsat images and performed a post-classification comparison strategy due to the availability of historical time-series data-set, after incorporating a supervised maximum likelihood classification algorithm.
Studies are limited to the geographical region of the Sangu River Basin located in the South-eastern corner of Bangladesh, while the current study will fill the gap. This study aims to apply a suitable methodology for forest cover and forest cover change mapping in the upper Sangu River Basin and to generate forest cover maps and forest cover change maps for the last few years.