Projected Risks to Biodiversity Conservation Along Brazil's Equatorial Margin Under Expanding Offshore Oil Development

ABSTRACT Brazil's Equatorial Margin is one of the least studied yet most ecologically significant regions of the Atlantic Ocean. Encompassing the Amazon coast, the region is entering a new phase of industrial expansion. In 2025, Brazil issued its first offshore oil exploration license in two decades, opening the door to large‐scale hydrocarbon development. This decision comes amid renewed global commitments to climate following COP30, highlighting persistent policy tensions between energy expansion and sustainability. Here, we present a spatially explicit assessment of cumulative oil spill risk across Brazil's Equatorial Margin. By integrating oceanographic modeling of spill trajectories with habitat distribution and vulnerability scores, we mapped cumulative risk across marine habitats in all sedimentary basins and identified where risk overlaps with conservation priorities. Results indicate that the Potiguar Basin contributes most strongly to cumulative risk for seagrass meadows, rhodolith beds, coral reefs, and seamount ecosystems. In contrast, the Foz do Amazonas Basin presents comparatively lower overall risk, although planned activities there increase projected risk for mesophotic reefs. Building on these insights, we outline policy actions—including strengthened ecological monitoring, improved spill preparedness, and expansion of marine protected areas—to improve governance as offshore oil development is considered along Brazil's Equatorial Margin.