Snapshots of coral reef biodiversity and challenges in a time of crisis

Coral reefs are sanctuaries for a large portion of our planet’s biodiversity, but their rapid decline begs critical questions about what exactly is being lost, what are the driving forces that determine decline or resilience, and what are the implications for life on Earth. To address these questions, we synthesize the state of knowledge on the diversity of coral reef life forms at different scales of biological and ecological organization, encompassing variability in genes, biomolecules, cells, organs, organisms, populations, communities, ecosystems, socio-ecosystems, and biogeoclimatic systems, with a particular focus on French tropical overseas. We discuss research pathways to address knowledge gaps in various scientific disciplines, covering genetics (genomics, transcriptomics, proteomics, metabolomics), morphology, ethology, bio-acoustics, demography, functional ecology, macro-ecology, landscape ecology, human and social sciences, bioclimatology, and their cross-disciplinary interactions. Based on contributions from a team of coral reef experts working in coral reef regions spread around the world, our synthesis supports a better understanding of the various dimensions of coral reef biodiversity and proposes future research orientations for improving our knowledge of nature and its preservation. Given the rapid decline of coral reefs, and how much is still unknown, this work underscores the urgency of cross-scale biodiversity investigations for a systemic understanding of the drivers of biodiversity distribution and dynamics.