Detecting flash drought impact on terrestrial ecosystems using observational data

Abstract

<p>Flash droughts are characterised by rapid onset and can therefore cause severe impacts on agriculture and ecosystems without sufficient early warning. The increasing occurrence of flash droughts due to climate change calls for a better understanding of the terrestrial ecosystem responses to flash drought events. Here we study the ecological impact of flash drought in Europe between 2001 and 2020. To do this, we define flash drought events based on soil moisture percentiles and compare temporal behaviours of various ecological data obtained from satellite observations and machine learning-supported upscaled in-situ measurements. We find that in arid regions, an abrupt transition to water-stressed conditions occurs within a few weeks, negatively affecting vegetation status and reducing carbon uptake in the initial stages of drought. By contrast, vegetation in humid regions is not as severely affected, given that soil moisture recovers relatively quickly. We also show that soil moisture status before the onset of drought significantly impacts the timing and degree of drought-induced vegetation stress, particularly in arid regions. Our study highlights the regional characteristics of flash drought impacts, contributing to better drought adaptation and management strategies. Moreover, our observational evidence of ecosystem responses to flash drought can be used as a reference to evaluate land surface models’ performance.</p>