Integrating the Unknowns Into Cumulative Human Impact Assessment Identifies Extensive Areas of Mangroves in Southeast Asia Under Human Pressure.

Mangroves provide critical ecosystem services, yet they face significant pressures from human activities. This study assesses cumulative human impacts on mangroves across Southeast Asia, using a Bayesian modeling framework to capture the hidden processes, such as stressor interactions or unmeasured stressors, and the variability and uncertainty in sensitivity weights and maximum effect distances from expert surveys. We identified 18 key stressors, with aquaculture ponds, nutrient pollution, cropland, and urban area as dominant contributors. Results indicate that extensive areas of mangroves in Southeast Asia (81.4%) are under cumulative human impact, with stark regional disparities. Hotspots of critical impact are concentrated in Vietnam's Mekong Delta, the Gulf of Thailand, urbanized regions in Singapore and Malaysia, and Java in Indonesia. Alarmingly, no intact mangrove areas were identified in Singapore, Vietnam, and Brunei. However, a notable positive finding is that several countries, including Brunei, Myanmar, Indonesia, Cambodia, East Timor, and Malaysia exhibit relatively low-impact scores. Furthermore, most countries are primarily affected by one or two dominant stressors, making it more feasible to design targeted conservation. The study underscores the importance of country-specific conservation strategies that account for the dominant stressors affecting each nation's mangrove ecosystems. By addressing methodological gaps while maintaining generalizability, our research advances cumulative impact assessment methodologies and provides valuable insights for the conservation, research, and management of mangrove ecosystems in Southeast Asia.