Testing new indicators for ecological resilience in a dryland mountain ecosystem using a multidecadal NDVI time-series

In this work, the ecological resilience to drought of a dryland catchment in the Moroccan High Atlas Mountains was studied. A time-series of Landsat NDVI data between 1984 and 2019 was used to determine areas of overall greening and browning. The Breaks For Additive Seasonal and Trend (BFAST) change detection methodology was used to determine breakpoints and trends in the time-series. The breakpoints were classified using a newly developed typology based on the trend before and after the breakpoint. The improved typology that is introduced, considers the statistical significance of trends, and subdivides them in categories of abrupt changes that lead to an improvement of ecosystem functioning (positive breakpoints) and abrupt changes that lead to a deterioration of ecosystem functioning (negative breakpoints). The ecological resilience in the catchment was explored using the number, sign and typology of the breakpoints detected and their relation to the various land uses and climatic zones of the catchment. In general, a small amount of change in NDVI between 1984 and 2019 was observed in the whole catchment. However, there was a large spatial variability in the number and type of breakpoints, pointing to the additional information provided by these indicators, which will be discussed in our presentation.