Remote sensing of peatland degradation in temperate and boreal climate zones – A review of the potentials, gaps, and challenges.

[Display omitted] • We present a 3D framework to evaluate peatland degradation research. • 54 % of 115 analyzed studies assess vegetation using space- or airborne optical data. • Research addressing vegetation, peat and hydrology in a tripartite system is rare. • Combined remote sensing sources allow more holistic peatland degradation research. Peatland degradation causes a number of environmental problems ranging from greenhouse gas (GHG) emissions to subsidence and ecosystem loss. Degraded peatlands, covering just 0.3 % of Earth's land area (500,000 km2), disproportionately contribute 5 % of GHG emissions, exacerbating the climate crisis. Once degraded, restoring peatland ecosystem functions often presents a considerable challenge because degradation affects several interconnected components in peatlands: the peat body, hydrology, and vegetation. The planning and implementation of effective peatland restoration strategies requires the accurate mapping of degradation. This review examines how remote sensing has been used to examine the components of peatland degradation. A conceptual 3D space was created using the three components of peat, hydrology, and vegetation. Within this three-dimensional space, five groups of studies were identified, representing each one of the three dimensions individually, or addressing two or three of them simultaneously. Of 115 relevant articles, 54 % solely addressed vegetation degradation, 18 % evaluated two dimensions equally, while just 10 % of all studies examined all three dimensions. These results highlight a lack of remote sensing-based research that considers all aspects of peatland degradation and their interdependence simultaneously. By synthesizing our findings into three descriptive peatland degradation scenarios (a boreal landscape, a temperate large peatland complex and a temperate small raised bog), we present rapid and efficient methods and resources for a more holistic approach to degradation mapping and monitoring. Consequently, such comprehensive assessments integrating different historical and current remote sensing data should be carried out more frequently. They allow the visualization of ecological consequences of peatland degradation and promote peatland restoration in all parts of these tripartite ecosystems. [ABSTRACT FROM AUTHOR]