Ayeyarwady kanazo swamp forest

ဧရာဝတီ ကနစို စိမ့်တောများ

Extinction Risk

National IUCN statusCR

Climate and ecology




Palustrine Wetlands

Functional Group

Tropical flooded forests and peat forests


Ayeyarwady kanazo swamp forest is an intertidal forest type dominated by the Endangered species Heritiera fomes (‘kanazo’, Stamp, 1925a). It occurs in the upper intertidal zone, normally above true mangroves, where the influence of freshwater is greater and water salinity is much lower than in seawater due to freshwater influx from the floodplain (Kathiresan et al., 2010). The ecosystem is characterised by a tree canopy of up to 25 m, the presence of pneumatophores and occasional flooding by fresh or saltwater (Stamp, 1925a; Davies et al., 2004).


Suitable habitat and historical records for this ecosystem occurs along the inland edge of the mangrove forest in the Ayeyarwady delta, and fragments may be expected to remain.


Native biota


The characteristic dominant tree species of Ayeyarwady kanazo swamp forest is Heritiera fomes, in association with Aglaia cucullata, Intsia bijuga and Barringtonia acutangula (Davies et al., 2004). These are freshwater mangroves and have morphological and ecophysical traits, such as pneumatophores, to tolerate substrate anoxia. Other woody species include Lagerstroemia speciosa, Hibiscus tiliaceus, and the palm Phoenix paludosa (Davis, 1960). At its lower elevation margins there are likely true mangrove species, including Sonneratia apetala.

Abiotic environment

Mean temperature

No data


Continual inundation results in substrate anoxia and peat accumulation


No data


Low elevation coastal zone


This ecosystem occurs in the low elevation coastal zone where it typically fringes the upper margins of the intertidal zone where waters may be mildly brackish to fresh (Kress et al., 2003). Continual inundation, particularly in the monsoon season, results in substrate anoxia and peat accumulation. The ecosystem can tolerate low levels of salinity, but generally occurs in the high intertidal zone, above true mangroves, where there is abundant freshwater inflow and groundwater seepage, and saltwater incursion is limited. Ayeyarwady kanazo swamp has very similar dynamics to adjacent Ayeyarwady delta mangrove forest. However, Stamp (1925) notes that kanazo typically requires daily tidal flooding, but must also completely dry for several hours at least twice daily. It does occur in areas that are flooded by freshwater for several months of the year, however, and therefore tends to occur as a fringing forest between mangroves and floodplain ecosystems (Stamp, 1924).

Key processes and interactions

Ayeyarwady kanazo swamp forest has similar processes and interactions as adjacent mangrove forests. It occurs on a marine- freshwater transition, upslope and inland of mangrove, where salinity is low, but varies according to seasonal monsoonal influx of freshwater from the river catchment, and daily tidal influence. Mangroves, particularly Sonneratia apetala occur in the transition zone, but diminish with increasing freshwater influence (Stamp, 1924b). As silt is collected by this vegetation and the sediment elevation increases, Sonneratia apetala is replaced by Kanazo (Heritiera fomes) in the higher elevation intertidal zone (Stamp, 1924).

Major threat

Major threat

Due to its occurrence around the upper intertidal zone, remaining Ayeyarwady kanazo swamp forest is highly threatened by coastal development for agriculture and aquaculture (Polidoro et al., 2010). Hertiera fomes is highly valued as timber, for which it is used for house building and boat building. It has also been widely used as fuelwood for more than a century and is considered the most favoured species for charcoal making. One estimate suggests that in 1919-1920, at least 250,000 tons of kanazo was illegally extracted from delta forest reserves (Bryant, 1996). These factors suggest it has probably been more widely deforested than adjacent mangrove forest ecosystems.

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

Ayeyarwady Kanazo Swamp Forest is thought to have undergone a major decline in extent around the early 20th century in response to overexploitation for fuelwood and proximity to Yangon (Stamp, 1924). It continues to be threatened by coastal development for aquaculture and agriculture, sea level rise and fuelwood extraction. Although no reliable data on its distribution is available, our broad analysis of global mangrove distribution data occurring within the area mapped as ‘Tropical Swamp Forest’ by Davis (1960) suggests that as little as 2.6% of this ecosystem may remain. With only one record in GBIF and no confirmed on-ground records, our estimate may be considered conservative. Thus, Ayeyarwady Kanazo Swamp Forest is considered Critically Endangered, with plausible bounds Critically Endangered – Collapsed.

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

This ecosystem is collapsed when its area has declined to 0 km2.

Date Assessed


Year published


Assessed by

Nicholas Murray

Reviewed by

David Keith

Contributed by

Robert Tizard