Flash drought drives rapid vegetation stress in arid regions in Europe

Abstract

Flash droughts are characterised by rapid onset, combined with the potential to severely impact agriculture and ecosystems. However, assessments of the ecological impacts of flash droughts, especially in Europe, are largely lacking. Here we investigate ecosystem responses to flash droughts in Europe between 2001 and 2019 using diverse observational data, including gross primary production (GPP) and leaf area index (LAI). We find that in arid regions an abrupt transition to water-stressed conditions occurs within a few weeks, which negatively affects vegetation status and reduces carbon uptake in the initial stages of drought; normalised anomalies of LAI and GPP decrease to about -0.5. 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 (1 to 5 pentads) and degree (-0.33 to -0.71 of normalised LAI/GPP anomalies) of drought-induced vegetation stress, particularly in arid regions. Our results highlight the regional characteristics of flash drought impacts for more informative monitoring and early warning systems.

Comparing Agriculture‐Related Characteristics of Flash and Normal Drought Reveals Heterogeneous Crop Response

“…(2013)'s findings that these regions are most sensitive to drought conditions. Our results are also consistent with O and Park (2023)'s findings that the flash drought onset—on which our study focuses—is strongly associated with increased vegetation condition in locations where soil moisture is sufficient for plant growth. Overall, irrigated agriculture seems to be more positively affected by flash drought, indicated by the steeper decrease in correlation between the drier and the wetter semiarid regions than in rainfed agriculture.…”

“…Drought characteristics were analyzed with respect to aridity to further contextualize the differences between flash and normal drought on agriculture, whether rainfed or irrigated. The aridity is an expression of average available energy and water over a longer time period—previous studies have indicated a relationship between aridity and vegetation response, with more arid regions typically exhibiting a quicker and stronger response of vegetation to dry conditions (O & Park, 2023; Orth et al., 2020; Vicente‐Serrano et al., 2013). Many of the characteristics have shown statistical differences between drought types and vegetation responses; however, the variable spatial distribution of these characteristics implies a spatial reason for these differences.…”

“…Other studies, such as Orth et al. (2020) and O and Park (2023), found that vegetation health indicators vary with aridity—in particular, that arid regions show strong responses and humid regions show weak ones—and that they intensify with increasing drought duration. This is consistent with Vicente‐Serrano et al.…”

“…While similar to drought in that they both express dryness, aridity is a descriptor of conditions without reference to typical levels-a key component of drought (Le Houerou, 1996)-and is typically calculated over longer periods of time (Zomer & Trabucco, 2022), making it a useful baseline for comparison between areas. Other studies, such as Orth et al (2020) and O and Park (2023), found that vegetation health indicators vary with aridity-in particular, that arid regions show strong responses and humid regions show weak ones-and that they intensify with increasing drought duration. This is consistent with Vicente-Serrano et al (2013), who found that regions with different aridity tend to respond to drought at different time scales, with arid regions responding faster than humid ones.…”

Wetness severity increases abrupt shifts in ecosystem functioning in arid savannas

“…Past studies have identified that very arid areas, like the savanna bioregions located in the west of South Africa, are particularly susceptible to significant shifts in vegetation due to climate changes (Assal et al., 2016; Sungmin & Park, 2023; Vetter, 2009). However, our findings contradict these earlier conclusions.…”