There is an urgent need to establish robust ecological baselines to monitor and anticipate the effects of anthropogenic pressures, including pollution and climate change, on South Atlantic ecosystems. These baselines are essential for guiding best-practice management and supporting local communities in adapting to environmental change. Despite growing awareness, significant knowledge gaps remain across marine, freshwater, and terrestrial habitats. Through our Ecosystems focal area, we harness expertise in fish ecology, seabird movement, peatland and wetland dynamics, and blue carbon systems to generate foundational biodiversity and ecosystem data. This work underpins environmental stewardship and sustainability across the South Atlantic UK Overseas Territories. By advancing evidence-based conservation and ecosystem-based management, our science increases the quality and accessibility of information available to researchers, practitioners, and decision-makers alike.