Drought-induced TREE MOrtalities and REwilding in Apulia (TREEMORE)

In the last 30 years the Mediterranean region has increasingly been subjected to prolonged droughts, a phenomenon expected to worsen due to the rising levels of anthropogenic emissions. Although the scientific community has reached an emerging consensus regarding the physical processes driving these extreme events - such as the increased frequency and duration of atmospheric blocking and the expansion of subtropical zones - the broader impacts of water shortages on vegetation and feedback mechanisms within the climate-environment system remain poorly understood. Current evidence suggests that drought may lead to widespread tree mortality, heightened wildfire risks, and a gradual transformation from Mediterranean ecosystems to vegetation types typically associated with semi-arid environments. Apulia region, in Southern Italy has been selected as the study region, as it offers a unique case study to assess the consequences of extensive olive trees die-off after the spread of the pathogen/bacteria Xylella fastidiosa. We will investigate the effect of die-off and of different potential replanting strategies on the regional atmosphere. The study involves three different vegetation scenarios with a total of 12 new high-resolution sensitivity experiments under low and high-emission conditions (RCP2.6 or SSP1-2.6 and RCP8.5 or SSP5 8.5). One scenario will act as a reference with the current vegetation state. A deforestation scenario, accounting for 100% desertification, will represent the worst-case scenario. A regreening scenario will represent the afforestation/rewilding with native Mediterranean vegetation over the whole region. For this work, we will employ the regional version of the Global Environmental Multiscale Model (GEM) over the Euro-Cordex domain and the high-resolution Regional Climate Model (RegCM5, Giorgi et al., 2023) in convection-permitting setup, configured for the Southern Adriatic region over the domain 39.5°N - 42°N, 14.5°E - 18.5°E. The simulations will facilitate an in-depth analysis of the climatic effects of altered vegetation cover, focusing on key variables such as mean and extreme temperatures and precipitation, moisture distribution, and convection. We aim at identifying climate resilient planting strategies (e.g. restoring the historical land use, olive groves, or the native mediterranean vegetation) in Apulia, as a potentially practical approach to counteract or alleviate the effects of future compound extreme events, including severe droughts and heatwaves.