Scoping review of early warning systems in improving disaster risk outcomes: perspective from evolution to usage in Southeast Asian countries

Abstract Background Between 1970 and 2019, Asia-Pacific region experienced dramatic increase in climate and weather-related disasters, with a five-fold increase in frequency compared to previous decades. Early Warning Systems (EWS) play pivotal role in mitigating impacts of such disasters, with global estimates indicating potential savings of US $3–16 billion annually. According to the World Meteorological Organization (WMO), effective EWS issued within 24 h can reduce disaster-related damage by 30%. However, limited evidence exists on the effectiveness and evolution of EWS in Southeast Asia. This scoping review aims to examine the development, components, and implementation of EWS in the region and assess their role in disaster risk reduction. Methods A comprehensive literature search was conducted using databases such as PubMed, Web of Science, and IEEE Xplore, and reports from global agencies including Emergency Events Database, Centre for Research on the Epidemiology of Disasters, World Resources Institute, and WMO. The inclusion criteria focused on English-language studies detailing design, implementation, or evaluation of EWS within Southeast Asian countries. Out of 3,039 initially identified records, 81 studies were selected and analyzed using descriptive synthesis. Results Asia-Pacific region remains the most disaster-prone area globally, impacting 6.9 billion people and causing over 2 million deaths between 1970 and 2020. In Southeast Asia alone, the average annual economic loss due to disasters is approximately US $86.5 billion, as reported in the Asia-Pacific Disaster Report 2019. Since the 2004 Indian Ocean Tsunami, substantial progress has been made in EWS development. The proportion of countries with multi-hazard EWS has risen from 25% in 2015 to 67% in 2023, facilitated by efforts such as the ESCAP Trust Fund and “Early Warnings for All” initiative. Conclusion This review elucidates the evolution of early warning systems (EWS) in Southeast Asia since 2004, highlighting technical and institutional advances alongside persistent gaps in awareness, last-mile dissemination, and community preparedness. Key barriers—limited multi-channel alerts, weak policy integration, and exclusion of vulnerable groups—undermine effectiveness. By leveraging SMS, community networks, participatory drills, and global best practices for inclusivity, the region can foster responsive, equitable systems that achieve “early warnings for all” and substantially reduce disaster risk.