Loss of Mangroves

Primary reference(s)

Kathiresan, K., and Bingham, B. L., 2001. Biology of mangroves and mangrove ecosystems. Accessed 21 January 2025.

Annotations

Key relevant UN convention / multilateral treaty

The Convention on Wetlands, adopted in 1971, was one of the earliest policy frameworks for the conservation and management of coastal wetlands, including mangroves (UNESCO, 1971). In 2015, the Sendai Framework for Disaster Risk Reduction (2015–2030) acknowledged, although not explicitly, the protective role of mangroves in the potential reduction of coastal disaster risks (UNDRR, 2015). Furthermore, the 2016 United Nations General Assembly resolution on oceans and the law of the sea (UN/A/RES/71/257) recognised the socio-ecological value of mangroves through the generation of vital ecosystem

Drivers

Mangroves are vulnerable to sea-level rise when they are unable to accrete sediments in pace with the sea-level rise, which results in their submergence and subsequent loss. This is compounded by their inability to migrate inland to higher elevations when suitable migration space is lacking due to coastal development or natural barriers, resulting in coastal squeeze (Alongi, 2015). Furthermore, mangroves are sensitive to other climatic events, such as storms, high water events, precipitation and drought, and climate fluctuations, such as the El Niño-Southern Oscillation (ENSO) (Field, 1995). Mangroves are most vulnerable when they experience combinations of these climatic events; for example, mangroves along a 1,000 km length in northern Australia recently experienced substantial dieback after an ENSO event led to a temporary sea-level drop and a marked reduction in precipitation (Duke et al., 2017).

The extent of mangrove loss varies regionally, with Southeast Asia representing a particular hotspot, accounting for 47% of the global net mangrove loss between 1996 and 2020, with the primary drivers of this loss also being regionally dependent (Bunting et al., 2022; UNEP-WCMC, 2014). Mangrove loss is primarily due to the deforestation of existing mangrove areas, with around 62% (Goldberg et al., 2020) attributed to aquaculture and agriculture (including oil palm, rice cultivation, and other forms of agriculture and undefined uses). Other significant causes include direct and indirect settlement (urbanisation), which involves the clearing of mangroves for housing and other infrastructure, and development activities that alter hydrology and sediment inputs, or create severe pollution, leading to mangrove loss (FAO, 2023). An estimated 26% of mangrove loss is also due to natural causes, which occur as a result of changes in riverbeds, sediment inputs, or sea level (FAO, 2023).

Impacts

The loss of mangroves and the ecosystem services they generate can negatively affect local coastal communities and global populations. These include reduced ability to mitigate climate change as a sink of atmospheric carbon; reduced disaster risk reduction and lower protection of coastal communities from hazards, such as sea-level rise and storm surges; reduced adaptive capacity of coastal populations through reduced access to sources of food, fibres, timber, chemicals, and medicines. The loss of these resources often translates into a loss of revenue, as local fisheries, tourism, and related industries are sustained by the mangrove forests. In addition, as mangroves store a large amount of carbon in their soils, mangrove deforestation can release 25–100% of the total cleared biomass as carbon dioxide (CO₂) emissions and as much as 45% of soil carbon is lost within three years (Lovelock et al., 2017). Emissions from wetlands are explicitly considered in national greenhouse gas emissions reporting through the Intergovernmental Panel on Climate Change. Mangrove loss may also have unintended impacts on other connected coastal ecosystems, such as seagrass meadows or coral reefs (UNEP-WCMC, 2006).  

Mangroves play a crucial role in mitigating the impacts of natural hazards, such as storms, floods, erosion, strong winds, and tsunamis. In that way, they contribute to disaster risk reduction. Studies indicate that ecologically healthy mangroves played a crucial role in saving lives and property during the tsunami (Danielsen et al., 2005; Goda et al., 2019). For example, during the 2018 earthquake in Palu Bay, Indonesia, tsunamis caused severe damage, with some areas experiencing waves as high as 2 metres. Homes located directly in front of mangrove forests were completely destroyed or swept away, while those sheltered behind the mangrove forests were largely spared (Goda et al., 2019). Similarly, the 2004 Indian Ocean tsunami showed that areas protected by mangroves suffered less damage than areas without such natural barriers (Danielsen et al., 2005). In Indonesia, land subsidence worsens the effects of sea-level rise on coastal ecosystems and communities, impacting both mangroves and coastal villages. However, mangroves experience subsidence to a lesser extent than villages, highlighting their protective role in reducing coastal flooding (Nurhidayah et al., 2022). A model also revealed that developing countries and small islands gain the most economic benefit from flood protection provided by mangroves. In Belize, Suriname, and Mozambique, these benefits represent over 15% of their national GDP (Menéndez et al., 2020). 

However, the loss of mangroves reduces their ability to provide protective services. As mangrove forests degrade or are lost, the natural buffer they provide against extreme events is lost (Goldberg et al., 2020). This, in turn, increases both the frequency and severity of damage caused by natural hazards and leaves coastal communities more vulnerable to disasters. Mangrove loss will eliminate their function as effective natural filters for chemical pollutants (Sultana et al., 2023), leading to a decline in water and sediment quality.

Multi-hazard context

The figure below summarises common interactions between the loss of mangroves and other hazards. This information should be used with caution and not be solely relied upon in Disaster Risk Management, particularly as some interactions may not have been included. Note that hazardous events occurring together or locally in space or time may not necessarily cause, amplify, or be otherwise related to each other. Specific examples of multi-hazard context can be found in the ‘Hazard drivers’ and ‘Impacts’ sections above.

Multi-hazard diagram

Risk Management

Mangrove loss can be reduced or managed by efforts to stabilise existing mangrove extent and restore (replant) mangroves that have been lost. Mangrove coverage can be stabilised by conservation efforts, including increased protected area management and enforcement of national laws that prohibit mangrove loss. Furthermore, it is important to integrate local knowledge and increase community participation. In addition, the promotion of flexible and robust governance is essential for dealing with uncertainty, complexity, and dynamics of mangroves and ecosystems (e.g. adaptive management). Investigating, monitoring, and mitigating drivers of mangrove loss on regional and national levels are critical to maintaining existing mangrove forests. 

Mangrove coverage can be increased by rehabilitation of previously deforested mangrove areas, such as the rehabilitation of abandoned aquaculture ponds. Potentially 800,000 hectares globally may be biophysically suitable for rehabilitation (Worthington and Spalding, 2018), although several socio-economic and governance challenges exist. These may reduce the area that is ultimately feasible to rehabilitate. The success of these interventions requires an expansion of research on the basic ecology and hydrology of mangroves and social sciences of human–mangrove interactions. Understanding local enabling conditions (social equity, environmental sustainability, and economic viability) is key to successful mangrove management and its associated blue economy. 

Mangroves play a crucial role in the resilience of coastal ecosystems, as they can adapt to rising sea levels through enhanced sedimentation. However, this ability can be suddenly lost, especially when mangroves experience long-term degradation. In such cases, ecosystems can rapidly revert to earlier conditions, leading to sediment loss and reduced functionality. To prevent this, early warning systems and monitoring are essential. These strategies help anticipate mangrove loss, enhancing ecological functions and services such as coastal protection and disaster mitigation. For example, in China, regular monitoring supports the development of tailored management measures, allowing for prompt responses to changes in ecosystem stability (Zheng, 2023). There are more datasets as well that could help comprehensive mangrove monitoring (Worthington et al., 2020).

Monitoring

No information available