The intensity and frequency of extreme climatic events, such as floods, heatwaves and extreme droughts, are increasing, along with their impact on society. Extreme climatic events (ECE) are responsible for significant economic losses worldwide. In Europe alone, ECE caused economic losses estimated at EUR 738 billion during 1980-2023. To face the effects of ECE, the European Commission adopted the European Strategy on Adaptation to Climate Change in 2021. The strategy aims to promote a faster, swifter and more systemic action to address the impacts of climate change.
Extreme climatic events can disrupt the temporal stability of ecosystem functions (e.g. plant biomass production), in turn also affecting ecosystems' ability to deliver services that support human well-being (e.g. food production). Biodiversity is thought to enhance ecosystems' response to extreme events. High biodiversity is expected to increase ecosystems' resistance (i.e. their capacity of buffering ECE) and recovery (i.e. their ability to return to pre-disturbance functioning after ECE). Different hypotheses have been proposed to explain how biodiversity supports ecosystems under ECE. However, only a few studies have empirically tested these hypotheses, and most have reported contrasting results. Possible explanations for the lack of consensus include: differences in spatial extent and, consequently, the type of data used to measure ecosystem functions and their stability (e.g. local studies using field-collected data vs. continental studies using remote sensing data); the use of unstandardized measures of intensity of ECE, which has likely hindered comparisons among studies; and a predominant focus on taxonomic diversity to explain biodiversity-mediated mechanisms of ecosystem stability. Concerning the last issue, neglecting the multifaceted nature of biodiversity may have limited our understanding of its role in mediating ecosystems' response to ECE. For example, incorporating functional traits in the picture could provide a more mechanistic understanding of how ecosystems respond to ECE.
In this context, COCOS aimed to address gaps and limitations in previous studies and provide a first assessment of the relationship between biodiversity and ecosystem stability under ECE at a broad spatiotemporal scale (Work Package 2). To this end, within COCOS, I used global, long-term time-series of field-collected vegetation data from the LOTVS dataset to measure ecosystem's resistance and recovery. I then combined these data with temperature and precipitation time-series to compute standardized indices of ECE intensity, thereby enabling comparison with future research. Importantly, I incorporated functional traits into the analyses to explain the biodiversity-stability relationship under ECE in light of species' ecological strategies. In addition to testing the association between biodiversity and ecosystem stability, COCOS aimed to investigate whether and how ECE can favor critical transitions, i.e. whether they can push ecosystems away from their reference state (and potentially toward a new reference state) (Work Package 3).
