Pressures on dryland ecosystems are ever growing. Large-scale vegetation die-offs, biodiversity loss and loss in ecosystem services are reported as a result of unsustainable land use, climate change and extreme events. Yet major uncertainties remain regarding our capability to accurately assess on-going land changes, as well as to comprehensively attribute drivers to these changes. Indeed ecosystem response to external pressures is often complex (e.g. non-linear) and non-unique (i.e. same response, different drivers). Besides critical knowledge on ecosystem stability and coping capacities to extreme events has still to be consolidated.Recent advances in time series analysis and in the assessment of breakpoint open a new door in ecosystem research as they allow for the detection of turning points and tipping points in ecosystem development (Horion et al., 2016 and 2019). Identifying ecosystems that have significantly changed their way of functioning, i.e. that have tipped to a new functioning state, is of crucial importance for Ecology studies. These extremes cases of vegetation instability are golden mines for researches that try to understand how resilient are ecosystems to climate change and to non-sustainable use of land.This is precisely what the U-TURN project is about:Developing methods for detecting turning points in dryland ecosystem functioning; Here we defined turning point in ecosystem functioning as a key moment in the ecosystem development where its functioning is significantly changed or altered without implying the irreversibility of the process (Horion et al. (2016), by opposition to the term 'tipping point' that implies irreversibility (Lenton et al. 2008). Studying the contribution of climate and human pressure (e.g. land-use intensification, human induced land soil degradation) in pushing the ecosystem outside its safe operating space; Here we used Earth Observation techniques coupled with Dynamic Vegetation Models to get process-based insights on the drivers of the observed changes in ecosystem functioning. Exploring whether early warning signal of turning points can be identified. During our talk, we will present key methodological advances being achieved within the U-TURN project, and showcase some of our major findings in relation to abrupt changes in dryland ecosystem functioning.References:Horion, S., Ivits, E., De Keersmaecker, W., Tagesson, T., Vogt, J., & Fensholt, R. (2019). Mapping European ecosystem change types in response to land-use change, extreme climate events, and land degradation. Land Degradation & Development, 30(8), 951-963. doi:10.1002/ldr.3282Horion, S., Prishchepov, A. V., Verbesselt, J., de Beurs, K., Tagesson, T., & Fensholt, R. (2016). Revealing turning points in ecosystem functioning over the Northern Eurasian agricultural frontier. Global Change Biology, 22(8), 2801-2817. doi:10.1111/gcb.13267Lenton, T. M., Held, H., Kriegler, E., Hall, J. W., Lucht, W., Rahmstorf, S., & Schellnhuber, H. J. (2008). Tipping elements in the Earth's climate system. Proc Natl Acad Sci U S A, 105(6), 1786-1793. doi:10.1073/pnas.0705414105 Project website: http://uturndryland.wixsite.com/uturnThis research is funded by the Belgian Federal Science Policy Office (Grant/Award Number:SR/00/339)