This Policy Brief shows the importance of cumulative pressures assessment (CEA) as the mechanisms of natural and anthropogenic change to the natural and societal marine environment. It explains why cumulative pressures from natural and human-induced change must be addressed in marine management. Practitioners increasingly have to manage activities and pressures in complex marine areas, and so this Policy Brief presents practical tools created by GES4SEAS to improve the knowledge-base in decision-making for comprehensive marine management. The tools link pressures and ecosystem components, visualise cumulative effects and integrate quantitative and qualitative information, even with limited data. They support policy-relevant applications to manage the causes and consequences of marine changes.