Mangroves are a vital part of coastal ecosystems, helping protect shorelines from erosion and storm impacts, providing habitat for fish and other wildlife, storing large amounts of carbon, and supporting livelihoods, food security and cultural traditions. Asia and the Pacific account for more than half of the world's mangrove share, making their resilience critical not only for biodiversity but also for the millions of people who depend on them. 

The IOD and El Niño are large-scale climate patterns that influence ocean temperatures, rainfall and sea levels across the Indo-Pacific region. They can create prolonged flooding, unusual heat and elevated salinity in coastal wetlands, placing significant stress on mangrove ecosystems, sometimes across multiple countries simultaneously. Acting independently or interacting, these two events have significant effects on ocean and coastal life. Understanding how they influence these local conditions is therefore essential to protecting mangroves and strengthening the resilience of coastal communities. 

Due to a positive IOD in 2020–2021, the Maldives experienced one of the most significant recorded mangrove dieback events in its history, with impacts reported on roughly one-quarter of the country's mangrove-bearing islands and losses exceeding 40 per cent of mangrove cover in some locations.  These were driven by raised sea levels, leaving many mangrove wetlands flooded for extended periods. In low-lying mangrove systems with poor drainage, seawater became trapped, evaporation concentrated salt in the soil, and tree roots were deprived of oxygen. This combination of flooding, heat stress and salt accumulation weakened and killed large numbers of mangroves. Sharing the same vulnerabilities, this positive IOD triggered widespread mangrove losses across the Western Indian Ocean, striking as far as the Seychelles, Comoros, Mayotte and Madagascar. Studies from other regions, including northern Australia during the 2015–2016 El Niño, have similarly linked these climate oscillations to large-scale mangrove dieback, demonstrating how such events can push already-stressed coastal ecosystems beyond their natural tolerance limits.

When a strong positive IOD occurs alongside El Niño, the combined effects have historically been associated with higher sea temperatures and sea levels, changes in rainfall, prolonged flooding in some areas and increased salinity in coastal wetlands. Many mangrove ecosystems are resilient and can recover from periodic climate fluctuations, but they have limits. Monitoring these large-scale climate patterns can provide valuable early warning and help coastal managers respond before ecological stress becomes widespread.  

Photo credit: Copilot/Leila Salarpour

The value of monitoring lies not in hindsight but in translating these signals into real-time, impact-based forecasts that coastal managers and sector users can act on in tandem with information regarding mangrove types and characteristics. In addition, protecting mangroves in a changing climate requires understanding new and recurring climate patterns that can rapidly push these ecosystems beyond their natural limits. 

ESCAP analysis of potential mangrove exposure to sea surface temperature anomalies finds that until 2040, mangroves in the Maldives are mostly under low or very low risk; but the pattern could shift to a medium level under SSP3-7.0 scenarios by 2060; and by the late century, exposure uniformly intensifies further to High under SSP2-4.5 and to Very High under SSP3-7.0. Understanding how mangrove ecosystems could respond over time is important for developing a strategic approach to mangrove preservation, such as allowing space for mangroves to adapt and migrate as shorelines change.

Development strategies should be less focused on reacting to individual events and more focused on strengthening long-term climate resilience. Protecting existing mangrove forests, as demonstrated by Malaysia's large-scale conservation efforts, restoring degraded ecosystems using locally appropriate approaches, such as Indonesia's mangrove rehabilitation and Sri Lanka's natural regeneration programme,  strengthening partnership and working with coastal communities, whose knowledge of local hydrology and environmental change is critical for successful restoration and long-term stewardship are some of the key elements that could ensure a sustainable approach to supporting mangroves.

While climate change is increasing uncertainty, as shown above, governments do not have to respond without guidance. Understanding recurring climate patterns alongside long-term climate trends can help coastal managers anticipate ecosystem stress and protect mangroves before irreversible damage occurs.