Evidence of the detrimental effects of climate change (CC) on forest viability is accumulating worldwide. One of the main causes of increased forest mortality is the emergence of maladaptation between the current genetic make-up of tree populations and the newly established climatic conditions. Disruptions in local adaptation have been observed in several species, which can lead to genetic erosion and local extirpation, especially when phenotypic plasticity is insufficient to confer tolerance to the new climatic conditions, the adaptive response is incompatible with the rate of environmental change, gene flow is insufficient to compensate for maladaptation, and human disturbance acts synergistically with CC through habitat degradation. Conservation of existing forest genomic resources (FGRs) has been recognised by the post-2020 global biodiversity framework as a guarantee that tree populations will retain sufficient adaptive potential in the face of CC. To this end, both genome-wide and functional variation need to be characterised and incorporated into conservation strategies, the former as a potential reservoir for future adaptation and the latter as a basis for local adaptation to historical habitat conditions. Strategies for evolutionary rescue include prioritising genetically diverse and differentiated populations and promoting ad hoc translocations of locally adapted populations to newly suitable sites (i.e. assisted migration). Based on the literature, genome-informed assisted migration is expected to result in a 10% increase in survival when the frequency of an adaptive allele is increased by nearly 50% in a target tree population. The MedForAct project aims to provide forest professionals with genome-informed guidelines for the conservation and management of FGRs in the Mediterranean region, a hotspot for forest genetic diversity and climate change. In particular, based on a pilot framework of three native pine species (Pinus halepensis Mill., P. pinaster Aiton and P. pinea L.) and extensive climatic and genetic sampling across the Italian peninsula, MedForAct will 1) identify functional variation that has promoted convergent local adaptation despite about 33 Myr of independent evolution in the dynamic geoclimatic context that has shaped the Mediterranean climate, and 2) develop a novel application for assisted migration that minimises maladaptation through a network of optimal genetic exchange between tree populations. As a result, the project is expected to help maintain key ecosystem services such as carbon sequestration, soil and coastal protection from erosion and salt spray, water filtration, food and recreational areas.
