Land cover degradation in the reference and monitoring periods of the SDG Land Degradation Neutrality Indicator for Switzerland

Abstract

Land degradation impacts most terrestrial biomes across all world regions. To address global change challenges emanating from degrading natural resources, many countries voluntarily set themselves the goal of achieving Land Degradation Neutrality (LDN). Baseline conditions are to be established over a reference period (2000 – 2015). With seven more years to monitor this Sustainable Development Goal 15 indicator — SDG15.3.1 until the year 2030, the scientific basis for operationalizing LDN is still evolving. The non-availability of annual land use-land cover maps of sufficient resolution in various countries, among them Switzerland, is a major factor hampering the assessment at national and local levels. Land cover change is assessed for seven land categories (that is, Tree-covered area, Grassland, Cropland, Wetland, Artificial Surfaces, Otherland, and Waterbody). Land cover change is a major LDN sub-indicator required to assess the proportion of degraded land to total land area (SDG15.3.1). Annual land cover datasets from 2015 to 2020 were produced at 10 m from Sentinel-1 and Sentinel-2 images using a Remote Sensing and Geographic Information System-based workflow. An evaluation of degradation in land cover is presented in support of the operationalization of LDN in Switzerland. Drawing upon the understanding that changes made to land use-land cover may act as precursors to land degradation processes, transitions relating to the loss of natural cover were identified based on the land cover change criteria during the reference and the monitored periods. The criteria were developed for relating land cover transitions to degrading and non-degrading processes. Such transitions were grasslands to tree-covered areas and croplands to artificial surfaces due to settlement development. For example, the amount of cropland converted to artificial surface areas was greater in absolute terms during the monitored period than during the reference period. Also, the regeneration of natural cover involving transitions from otherland to grassland and from grasslands to tree-covered areas was found. Overall trends between 2000 and 2020 in Switzerland are the increasing settlement areas in the Central Plateau, the Alpine valleys of Valais and Ticino, largely at the expense of croplands and the bush encroachment of pastures such as in the Jura. This study’s contributions include an enhanced workflow for annual land cover mapping for the entire Switzerland and the adaptation of the land cover change criteria to fit the Swiss context. The proposed mapping method has the potential to fill the gap between the production cycles of the Swiss Corine and Arealstatistik land use data.