The Agricultural Land Abandonment and Climate Change Impacts on the Water, Energy and Vegetation Carbon Cycles in the Mediterranean Region - ESA X-ECV GLANCE Project

In recent decades, the Mediterranean region (MR) has emerged as a critical hotspot for both climate change (Giorgi, 2006; Cramer et al. 2018, IPCC, 2023) and land abandonment (Herrando et al., 2016; Lasanta et al. 2017, Jiménez-Olivencia et al., 2021). Only in Europe, approximately 120 million hectares of land have been abandoned, primarily due to socio-economic factors such as rural migration to areas offering better economic opportunities — a trend particularly pronounced in the Mediterranean.  Following World War II, traditional agro-pastoral activities in the Mediterranean began to decline, driven by significant socio-economic shifts and the subsequent economic boom. As a result, rural areas and grazing lands in most of the Mediterranean mountain areas of the northern part of the basin have experienced widespread natural reforestation (Mottet et al., 2006). This, along with a significant rise in atmospheric evaporative demand due to climate change has triggered complex and poorly understood effects on the carbon, water, and energy cycles that will be studied by GLANCE.  The main goal of GLANCE is to leverage ESA CCI ECVs for the quantification of the effects of climate change and land abandonment on forest carbon dynamics, water and energy cycles in the Mediterranean Region. GLANCE aims at answering the following research questions:   1. How much, where and what type of Mediterranean forests have expanded in the past couple of decades?   2. How has forest expansion due to land abandonment and climate change impacted water, energy and carbon cycles especially during major drought events?   3. Which is the sensitivity of a change in runoff, groundwater recharge, evaporation, net and gross primary productivity, water use efficiency to changes in forest cover under land abandonment and climate change?  GLANCE will achieve its objectives through:   1. Utilizing past and ongoing ESA CCI and other ESA initiatives within an integrated framework to analyse long-term observations (at least 30 years) of forest carbon and water–energy cycle dynamics at the MR.   2. Employing tools, data and methods to accurately assess the uncertainties associated with each ESA CCI dataset and derived products utilizing (i) collected benchmark data from the GLANCE database, (ii) error propagation techniques (e.g., Montecarlo approaches), Triple Collocation techniques and iii) cross- comparison among the existing observational products and reanalyses.   3. Employing state-of-the-art trend analysis, drought indices, and climate elasticity to uncover the impacts of land use changes on forest carbon and water cycle dynamics over the past three decades in the MR. In this contribution we provide an overview of the project, and the main results achieved. Giorgi, F., 2006. Climate change hot‐spots. Geophysical Research Letters 33, 2006GL025734. https://doi.org/10.1029/2006GL025734 Cramer, W., Guiot, J., Fader, M., Garrabou, J., Gattuso, J.-P., Iglesias, A., Lange, M.A., Lionello, P., Llasat, M.C., Paz, S., Peñuelas, J., Snoussi, M., Toreti, A., Tsimplis, M.N., Xoplaki, E., 2018. Climate change and interconnected risks to sustainable development in the Mediterranean. Nature Clim Change 8, 972–980. https://doi.org/10.1038/s41558-018-0299-2 Intergovernmental Panel On Climate Change (Ipcc), 2023. Climate Change 2021 – The Physical Science Basis: Working Group I Contribution to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, 1st ed. Cambridge University Press. https://doi.org/10.1017/9781009157896 Lasanta, T., Arnáez, J., Pascual, N., Ruiz-Flaño, P., Errea, M.P., Lana-Renault, N., 2017. Space–time process and drivers of land abandonment in Europe. CATENA 149, 810–823. https://doi.org/10.1016/j.catena.2016.02.024 Herrando, S., Brotons, L., Anton, M., Páramo, F., Villero, D., Titeux, N., Quesada, J., Stefanescu, C., 2016. Assessing impacts of land abandonment on Mediterranean biodiversity using indicators based on bird and butterfly monitoring data. Envir. Conserv. 43, 69–78. https://doi.org/10.1017/S0376892915000260 Jiménez-Olivencia, Y., Ibáñez-Jiménez, Á., Porcel-Rodríguez, L., Zimmerer, K., 2021. Land use change dynamics in Euro-mediterranean mountain regions: Driving forces and consequences for the landscape. Land Use Policy 109, 105721. https://doi.org/10.1016/j.landusepol.2021.105721 Mottet, A., Ladet, S., Coqué, N., Gibon, A., 2006. Agricultural land-use change and its drivers in mountain landscapes: A case study in the Pyrenees. Agriculture, Ecosystems & Environment 114, 296–310. https://doi.org/10.1016/j.agee.2005.11.017