Using satellite data to assess management frequency and rate of regeneration on heather moorlands in England as a resilience indicator

Peatland resilience, defined here as the rate of recovery from perturbation, is crucial to our understanding of the impacts of climate change and land management on these unique ecosystems. Many peatland areas in the UK are managed as grouse moors using small burns (or increasingly, heather cutting) to encourage heather growth and limit fuel load. These small burns or cuts are distinct disturbance events which provide a useful means of assessing resilience. Until now, it has been difficult to monitor the area affected by management each season due to the remoteness and size of moorland sites. Newer satellite sensors such as those on Sentinel-2 are now collecting data at a spatial resolution that is fine enough to detect individual burns or cut areas, and at a temporal resolution which can be used to monitor occurrence and recovery each year. This study considered four areas of moorland; the North Pennines, Yorkshire Dales, North York Moors, and the Peak District. For each of these areas Sentinel-2 optical data was used to detect management areas using the dNBR (differenced Normalized Burn Ratio), and to monitor vegetation recovery using the NDVI (Normalised Difference Vegetation Index). Significant differences were found between the four selected sites in management repeat interval, with the North York Moors having the shortest repeat interval of 20 years on average (compared to 40–66 years across the other three study sites). Recovery times were found to be affected by burn size and severity, weather during the summer months, and altitude. This suggests that the interactions between peatland management and climate change may affect the future resilience of these areas, with hot, dry summers causing longer management recovery times.