Multi-year droughts (MYDs), droughts that last more than a year, can have devastating effects on vegetation. Due to climate change, MYDs are expected to become more frequent and intense, making it crucial to assess and understand their impact on vegetation in more detail. In this study, we used ERA5 meteorological reanalysis and MODIS remote-sensed observational data to assess the sensitivity of vegetation to droughts and to quantify the impact of MYDs on seven different vegetation types in specific regions across the globe. We first assessed drought sensitivity by calculating the Enhanced Vegetation Index (EVI) anomaly across different drought timescales. Subsequently, we evaluated the impact of MYDs and normal droughts (NDs) by averaging the EVI anomaly during their respective periods. Our analysis shows that croplands, urban areas, and shrublands are highly sensitive to drought, while grasslands and trees are less so. As anticipated, the overall impact of MYDs on vegetation was negative, but our findings reveal significant spatial and temporal variations with some areas showing significant greening during these periods. In general, shrublands experienced the largest decrease in greenness, while trees flourished. The natural water availability of a region is the primary factor influencing vegetation response to MYDs. Vegetation in water-limited areas tends to suffer during MYDs, whereas vegetation in energy-limited areas thrives as long as sufficient water is available. When compared to the impact of NDs on vegetation, MYDs generally have a more negative impact. Overall, these findings show that there is no unidirectional response of vegetation to MYDs and that local factors, like natural energy and water availability, play a vital role in quantifying the complex interplay between drought and its impacts on vegetation.
Multi-year droughts (droughts that last more than a year, MYDs) can severely harm vegetation, and their frequency and intensity may increase due to climate change. It is essential to understand how MYDs affect vegetation to manage their impacts better. In this study, we used meteorological and satellite data to assess the sensitivity of vegetation to droughts and to quantify the impact of MYDs on different vegetation types in six regions across the globe. To do this, we first looked at how sensitive different types of vegetation are to droughts by measuring changes in the Enhanced Vegetation Index (EVI) anomaly at various drought durations. Next, we assessed the effects of MYDs and normal droughts (NDs) by calculating the average EVI anomaly during these drought periods. As can be expected, MYDs have a negative effect on vegetation in general, but we also found large areas where MYDs cause vegetation to become greener. Our results highlight that croplands, urban areas, and shrublands are highly sensitive to drought, the latter showing largest decrease in greenness, while grasslands and trees are less affected and sometimes even thrive. Compared to NDs, MYDs typically have a more negative impact on vegetation. Our findings highlight that vegetation response to MYDs is complex and depends not only on vegetation type but also on local factors such as energy and water availability found in the different regions.