Droughts are becoming increasingly common across Europe, due to the changing climate. In particular, certain regions are experiencing increased intensity, duration, and frequency of droughts, leaving a significant impact on society and ecosystems.
Reduced vegetation productivity, shifts in vegetation composition, loss of biodiversity, and a decline in essential ecosystem services, follows in the aftermath of droughts with dire social, ecological and economic consequences. During 1981–2010, the annual economic loss due to drought in Europe and the UK reached a staggering 9 billion euros, with agriculture accounting for half of these losses. This highlights the urgent need for preparedness and a deeper understanding of how vegetation responds to drought.
Sub-seasonal drought sensitivity revealed
To gain a comprehensive understanding, researchers utilized in this study an array of remotely sensed vegetation indicators combined with climate data to examine how vegetation responds to drought across European biomes during the period from 2000 to 2020.
The results show that vegetation's correlation with drought varies in strength depending on the time scale and month of the year with the proportion of land susceptible to drought rises significantly during the peak growth months of summer and the autumn senescence. As the vegetation develops from spring to autumn, the sensitivity to meteorological drought increases, across all 7 investigated biomes, although the strength and time scale differs across regions. Although soil water shortage strongly affects vegetation growth, the vegetation sensitivity to meteorological drought is is mainly related to vapor pressure and to some extent to the CO2 concentration in the atmosphere.
The strongest sensitivity to drought is found in southern and central Europe cropland, grassland, and deciduous forests. In contrast, evergreen needle leaf forests, which dominate northern Europe, appear less affected by drought. In northern Europe, wetlands were the biome most sensitive to drought.
Addressing the research gap
The study also addresses a notable research gap. Historically, much of the research focused on overall annual vegetation responses to drought and recovery post-drought. However, the immediate sub-seasonal responses across large scales have often been overlooked. This oversight is significant because understanding how drought affects vegetation growth at an ecosystem level is vital for crop planning, efficient water resource management, ecosystem restoration, and drought risk mitigation.
- The most important is the finding that drought response varies significantly across European biomes and by growing season. The information can strengthen the information base for planning of water management and drought responsiveness. Creating a more resilient society is a long process that requires thoughtful and thorough planning based on many scientific studies before it can be implemented. However, the work needs to be started now, says professor Lars Eklundh, from the department of Physical Geography and Ecosystem Science.
Implications and the way forward
Understanding these dynamics has far-reaching implications. It underscores the need for water management strategies, particularly during late growing seasons, to enhance primary production, carbon sequestration, and crop yields. In a changing climate scenario marked by wet springs and dry summers, such strategies become even more critical. The higher sensitivity of plants to drought stress (plasticity) during the autumn mature stage, in contrast to their lower sensitivity (rigidity) during the spring "infant" stage, could represent a natural survival strategy for both individual plants and communities across European biomes. However, whether this holds true on a global scale remains uncertain.
In conclusion, this research offers critical insights into the immediate impact of meteorological drought on vegetation across Europe. By shedding light on vegetation's responses to drought and its complex relationship with soil moisture, vapor pressure deficit, radiative energy, and atmospheric CO2, this study equips us with further knowledge needed to navigate the challenging terrain of a changing climate.
The article is published in Nature Communications Earth & Environment, August 2023; contact is Hongxiao Jin at the Department of Physical Geography and Ecosystem Science at Lund University.