Harnessing macrogenomics to study changing marine ecosystems under global climate change.

Climate change is reshaping marine ecosystems at an accelerating pace. Predicting its impacts on biodiversity and ecosystem functions is therefore crucial to developing effective conservation strategies. Integration of genomic tools, habitat modelling and simulations offers a transformative approach to forecast these impacts. Yet, current frameworks remain limited to single-species analyses. In this review, we discuss future directions in the emerging field of macrogenomics, the analysis of large-scale genomic data across species and time, and show how its integration with environmental data can be applied to understand past and predict future climate-driven ecological shifts across entire marine communities. We demonstrate how applying a macrogenomic framework can provide insights into future responses of marine ecosystems under global climate change by integrating multi-species demographic analyses, metagenomics and signatures of adaptation associated with past climate fluctuations. We also show how macrogenomics combined with predictive approaches can be used to forecast cascading effects of species fluctuations on ecosystem structure and potentially identify ecosystem tipping points. Ultimately, coupling empirical and prediction data offers a powerful approach for ecosystem-based management, improving our ability to predict adaptive responses and extinction risks at relevant scales, and equipping managers and policymakers with actionable insights to prioritize biodiversity conservation strategies.