Ayeyarwady delta mangrove forest

ဧရာဝတီ မြစ်ဝကျွန်းပေါ် ဒီရေတော

Extinction Risk

National IUCN statusEN

Climate and ecology




Brackish Tidal Systems

Functional Group

Intertidal forests and shrublands


Ayeyarwady delta mangrove forest is dominated by trees tolerant of salinity, tidal inundation and substrate anoxia. Salt tolerance is conferred by osmotic regulation and salt excretion. Specialised structure such as aerial stilt roots, lenticels and aerenchymatous tissues transport oxygen to roots. High primary productivity and litter fall sustains a web of detritivores and their predators. At high tide, mangroves are important nursery grounds for juvenile fish (Spalding, 2001).


Ayeyarwady delta mangrove forest occurs in the intertidal zone across the Ayeyarwady Delta, which is defined by Cape Negrais in the west and the Thanlwin (Salween) River in the east. This ecosystem was originally the largest tract of mangroves in Myanmar (Webb et al., 2014). The earliest reliable area estimate (1978) for the total mangrove distribution in the Ayeyarwady Delta was 2,623 km2 (Webb et al., 2014), though other accounts suggest that mangroves may have covered 2,345 km2 in 1954 (Oo, 2002).


Native biota


Complex forest composed of trees from multiple taxa including Rhizophora apiculata, Avicennia officinalis, Bruguiera sexangular, Excoecaria agallocha and Sonneratia caseolaris. Up to 33 mangrove species have been recorded in this system (U Win Maung, pers. comm.) out of a total of 34 recorded nationally (Aye et al., 2019). Nypa fruticans may occur in the upper intertidal zone where there is more freshwater influence, although its presence may have increased in response to human disturbance. The area provides habitat for several threatened vertebrates, including Irrawaddy dolphin Orcaella brevirostris (EN), Estuarine crocodile Crocodylus porosus and Mangrove Terrapin Batagur baska (CR). There is a small group of mangrove specialized breeding birds including Brown-winged Kingfisher Pelargopsis amauroptera (NT), Ruddy Kingfisher Halcyon coromanda, Mangrove Pitta Pitta megarhyncha (NT), and Mangrove Whistler Pachycephala cinereal (Rasmussen and Anderton, 2012). Migratory shorebirds may also be present in this ecosystem, utilizing vegetation for roosting habitat and foraging among the aerial roots and pneumatophores at low tide (Hogarth, 2015). There are relatively few mammals in the area but Smooth Otter Lutrogale perspicillata (VU) and Fishing Cat Prionailurus viverrinus (VU) have both been recorded (Francis, 2019).

Abiotic environment

Mean temperature

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Mangroves occur in coastal areas where they are inundated by seawater during the diurnal tidal cycle. This high salinity environment generally occurs along the coastal fringe, and is important for reducing incursion of other non-halophytic vascular plants (Marshall et al., 2018). Being well adapted to highly saline

Key processes and interactions

The mangrove trees drive most of the processes and functions in this ecosystem, providing nursery habitat for fish and shrimp, controlling and responding to sedimentation processes and generating organic matter that contribute to carbon and nutrient cycles (Marshall et al., 2018). In general, mangrove distribution is constrained by cool temperatures (Figure 1), but these are not limiting in Myanmar. They are also regulated by wave action, tides and sea level (Figure 1).

Major threat

Major threat

The Ayeyarwady Delta has undergone extensive deforestation as a result of high human population (around 8 million people) and widespread agricultural development (Oo, 2002; Webb et al., 2014). The delta region hosts around 14% of Myanmar's population and is responsible for around 35% of the country's rice production (Webb et al., 2014). Rice is thus a well-documented threat to mangroves in the region, primarily driving widespread deforestation and modification of hydrology (Webb et al., 2014; Richards and Freiss, 2016). Mangrove deforestation as a result of aquaculture, salt farming and fuelwood extraction have also been documented throughout the Ayeyarwady delta region (Webb et al., 2014; De Alban et al., 2020).

Instruction: The visualization shows threats that are present within each ecosystem. According to IUCN, direct threats are the proximate human activities or processes that have impacted, are impacting, or may impact the the status of the taxon being assessed. Click of the highlighted icons to see details each threat category.

Ecosystem Assessment

Assessment Summary

Published estimates of the reduction in geographic distribution suggest that extensive losses of this ecosystem have occurred. Using rates of change from a long-term time-series remote sensing dataset suggests that a decrease in extent of around 79.5% is expected over a 50 year period between 1978 and 2028. However, there are challenges in linear extrapolations from historical data into the future, since the Ayeyarwady is undergoing rapid socioeconomic changes which may mean a non-linear response in the future. Even with this uncertainty, the ecosystem qualifies as Endangered under criterion A2b, and just under the threshold for Critically Endangered. Endangered.

Instruction: Click on the chart to view the detailed assessment result for each RLE risk criteria. Risk is defined as the probability of an adverse outcome over a specified time-frame. Here, the adverse outcome is the endpoint of ecosystem decline, which the RLE terms ecosystem collapse.

Ecosystem collapse definition

We follow the collapse definition of Marshall et al. (2018), where an absence of true mangrove species signifies transition to a collapsed or novel ecosystem. Therefore, this system is considered collapsed when the distribution of mangroves declines to 0 km2. This is a conservative threshold because established trees may persist for some years after the site becomes unsuitable for reproduction and recruitment.

Date Assessed


Year published


Assessed by

Nicholas Murray,Thomas Worthington

Reviewed by

David Keith

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