Mega deltas are critical interfaces linking river basins and the ocean. They are cradles of human civilization, centers of population and economic activity, and strategic regions for achieving the United Nations Sustainable Development Goals. Sustained by freshwater, sediment, and nutrient inputs from vast river basins, as well as ecosystem services provided by adjacent coastal and marine environments, mega deltas support regional economic development, food security, ecological security, and human well-being. However, climate change and human activities are increasingly altering river discharge, sediment transport, and land–sea material exchanges through water regulation, dam construction, land-use change, and pollution. At the same time, sea-level rise, more frequent extreme events, coastal erosion, and ecosystem degradation pose growing threats to delta stability, coastal resilience, and nearshore environmental health. Addressing these interconnected challenges requires stronger collaboration among stakeholders across river basins, deltas, and coastal zones, and the development of integrated land–sea governance approaches for sustainable development.

The United Nations Decade of Ocean Science for Sustainable Development (2021–2030) promotes science-based solutions for a sustainable ocean. Within this framework, the Mega Deltas Programme advances international cooperation, knowledge sharing, and innovation for climate adaptation, ecosystem conservation, risk reduction, and sustainable development in major delta regions worldwide. In parallel, the United Nations International Decade of Sciences for Sustainable Development (2024–2033) supports the Land–Sea Dialogue for Coastal Sustainability (CROSS-Coasts) programme, which emphasizes systems-based approaches to strengthen coordination among estuaries, coastal zones, and adjacent marine ecosystems, while engaging scientists, policymakers, businesses, and society in addressing sustainability challenges.

Under these international initiatives, the 5th International Conference on Mega Deltas and Coastal Sustainability will bring together scientists, policymakers, practitioners, business leaders, and representatives of international organizations from river basins, deltas, and coastal regions worldwide. Participants will share scientific advances, governance experiences, and innovative practices related to environmental change and sustainable development in coupled river basin–delta–coastal systems, and explore solutions that contribute to the achievement of the Sustainable Development Goals.