In the face of climate change, we need to understand the drivers of changes in forest composition. Functional traits hold great promise as a way to explore and depict how the interplay of species climate stress tolerance and competition drives these changes. To date, progress has, however, been limited because we have a poor understanding of how traits control tree demography. DECLIC will build on the increasing availability of forest inventory data documenting tree demography and the emergence of key physiological traits directly linked to survival to determine how those traits control tree demography response to drought, frost, and competition in Europe and North America. This will allow us to develop size-structured community assembly models predicting forests dynamics along climatic gradients based on species traits. These models will be used to derive metrics of forest vulnerability to climate change such as evaluations of the risk of forest dieback, productivity decline and regeneration impeding at the scale of French ‘sylvoécoregions’. Then we will co-construct with French forest managers the best approach to present these metrics and their uncertainty on a web-platform adapted to disseminate them broadly.

Coral reefs are important biodiversity hotspots and major ecological reserves. They are also critically important to the many countries living nearby. With global warming, extreme thermal events called Marine Heat Waves (MHWs), have devastating effects on coral reefs, inducing massive bleaching (i.e. symbiosis disruption between corals and their Symbiodiniaceae algae, depriving the coral of its main food source). Bleaching can lead to coral death if the stress persists, unless corals can rely on their heterotrophic nutrient acquisition, by consuming organic matter or planktonic preys. There is evidence that some coral communities, living in mesotrophic reefs (rich in plankton and nutrients) are less sensitive to bleaching. In laboratory, corals supplied with plankton are more resistant to heat stress but fewer studies have been conducted in the field. While MHWs are becoming more frequent and intense, areas rich in plankton and organic matter (hereafter called mesotrophic reefs) can be key to coral survival by allowing corals to obtain external energy sources. They can serve as coral refuge in the face of climate change. BOOST gathers four UMRs (ENTROPIE, LEMAR, MIO, LOMIC) and three international partners, the CSM, Duke University and KAUST on a highly multidisciplinary project merging ecophysiology, biogeochemistry, oceanography and remote sensing. Laboratory and in situ approaches are applied in BOOST to: (1) (a)Determine whether mesotrophic reefs show higher metabolic performances, and (b) whether corals from oligotrophic reefs can adapt to mesotrophic conditions, by measuring in particular their productivity and calcification with innovative equipment using high-frequency sampling, and by transplanting corals from oligo- to mesotrophic reefs and assess their physiological parameters; (2) Confirm, under in situ conditions, that corals from mesotrophic reefs are more resistant to bleaching by performing short-term acute heat stress on corals collected either in meso- or oligotrophic reefs and transplanted from an oligotrophic reef; (3) Assess that coral tissue properties reflect the seawater nutrient properties and enable the determination of coral heterotrophic levels in situ by measuring new heterotrophic markers (bulk isotopic d13C and d15N values, some d15N-compound-specific amino acid values and a fatty acid biomarker (cis-gondoic acid)) calibrated in corals cultivated in laboratory conditions, under different diets; (4) Localize other mesotrophic reefs, where corals may be more resistant to future MHWs, by analyzing satellite images of surface chlorophyll-a around New Caledonia. BOOST will provide new tools to help policymakers and environmental managers decide where to focus their efforts to preserve areas more resilient to climate change, and thus essential for reef protection and restoration. BOOST results can be combined with other “Nature Based Solution” to improve reef restoration strategies and may even make it possible to consider seeding some coral reef portions with plankton or organic matter.