Identification of typical ecohydrological behaviours using InSAR allows landscape-scale mapping of peatland condition

Abstract

Better tools for rapid and reliable assessment of global peatland extent and condition are urgently needed to support action to prevent further decline of peatlands. Peatland surface motion is a response to changes in the water and gas content of a peat body regulated by the ecology and hydrology of a peatland system. Surface motion is therefore a sensitive measure of ecohydrological condition but has traditionally been impossible to measure at the landscape scale. Here we examine the potential of surface motion metrics derived from satellite interferometric synthetic aperture radar (InSAR) to map peatland condition in a blanket bog landscape. We show that the timing of maximum seasonal swelling of the peat is characterised by a bimodal distribution. The first maximum, usually in autumn, is typical of “stiffer” peat associated with steeper topographic gradients, peatland margins, and degraded peatland and more often associated with “shrub”-dominated vegetation communities. The second maximum, usually in winter, is typically associated with “softer” peat typically found in low topographic gradients often featuring pool systems and Sphagnum-dominated vegetation communities. Specific conditions of “soft” and “stiff” peats are also determined by the amplitude of swelling and multi-annual average motion. Peatland restoration currently follows a re-wetting strategy; however, our approach highlights that landscape setting appears to determine the optimal endpoint for restoration. Aligning the expectation for restoration outcomes with landscape setting might optimise peatland stability and carbon storage. Importantly, deployment of this approach, based on surface motion dynamics, could support peatland mapping and management on a global scale.