Classification Methods for Detecting and Evaluating Changes in Desertification-Related Features in Arid and Semi-arid Environments

Abstract

Land cover, land use, soil salinisation and sand encroachment, which are desertification-indicating features, were integrated into a diachronic assessment, obtaining quantitative and qualitative information on the ecological state of the land, particularly degradation tendencies. In arid and semi-arid study areas of Algeria and Tunisia, sustainable development requires the understanding of these dynamics as it withstands the monitoring of desertification processes. Two different classification methods of salt and sand features have been set up, using historical and present Landsat imagery. Mapping of features of interest was achieved using both visual interpretation and automated classification approaches. The automated one implies a decision tree (DT) classifier and an unsupervised classification applied to the principal components (PC) extracted from Knepper ratios composite. Integrating results with ancillary spatial data, we could identify driving forces and estimate the metrics of desertification processes. In the Biskra area (Algeria), it emerged that the expansion of irrigated farmland in the past three decades has been contributing to an ongoing secondary salinisation of soils, with an increase of over 75%. In the Oum Zessar area (Tunisia), there has been a substantial change in several landscape components in the last decades, related to increased anthropic pressure and settlement, agricultural policies and national development strategies. One of the concerning aspects is the expansion of sand encroached areas over the last three decades of around 27%. This work is partly supported and developed within the WADIS-MAR Demonstration Project, funded by the EU Commission through the SWIM Programme (www.​wadismar.​eu)

Land cover change of arid environment in Tunisia based on analysis of Landsat images

“…We used two ETM + images in 05 May 2000 and 09 April 2008, and one OLI image in 02 April 2014. The climate data were taken into consideration when choosing the imagery acquired during this season, as it has been reported by Elnaggar and Noller (2010); Afrasinei et al (2017), that this period was the most suitable period of year to detect land cover changes and sand encroachment and easily visualise them in this region.…”

“…Land cover mapping and change detection using remote sensing data sets and geographic information systems (GIS) techniques have significantly helped understanding the LC alteration processes and change and their consequences in arid and semi‐arid regions in Tunisia using Landsat satellite historical imagery missions for the last five decades (Afrasinei et al, 2017; Bachir, Essifi, Zerrim, & Ouessar, 2013; Essifi, Ouessar, & Rabia, 2009; Ouerchefani, Dhaou, Delaitre, Callot, & Abdeljaoued, 2013). Furthermore, LC classification has a high potential for monitoring land degradation and climate‐related disasters (Bouaziz, Eisold, & Guermazi, 2017).…”

Flowered-Geodbapp: An Application Based on Crowd-Generating Data Using Sentinel2 Imagery

“…Changes in land use in the study areas are very quick as they are linked to local climate conditions. Moreover, as in other countries soil salinization, deforestation and forest fires are very common and can modify the land use of local communities (Afrasinei et al, 2015(Afrasinei et al, , 2017 . In Figure 4 the flow chart of the steps of the maps production is shown.…”

Development of Desertification Indicators for Desertification Monitoring from Landsat Images Using Python Programming

“…Desertification is one of the main defiance that is facing the activities of development in several areas worldwide (Ahmed, 2015). It is recognized as a serious ecological, environmental, and socio-economic threat to the world, and there is a pressing need to develop method to assess it at different scales (Lamchin et al, 2016) because it threaten the sustainability and reliability of economic growth and its monitoring is an indispensable requirement for reviewing and improving resource management (Afrasinei et al, 2017). Desertification has been defined as the land degradation in arid, semi-arid and dry sub-humid areas due to climate variation and/or human activity by the United Nations Convention to Combat Desertification (UNCCD, 1994).…”