Irrawaddy moist deciduous forests
The Irrawaddy Moist Deciduous Forests are a unique ecological region located in central Myanmar, covering approximately 53,400 square miles (138,300 square kilometers). This biome is situated within the Irrawaddy river basin, which includes significant tributaries such as the Chindwin, Salween, and Sittang rivers. The forests thrive on hilly slopes and well-drained lands, characterized by a tropical climate with distinct wet and dry seasons, and experience an average annual rainfall of around 59 inches (150 centimeters).
The flora of the region includes notable tree species such as teak and pyinkado, which are economically important for timber exports. The forest supports a rich biodiversity, with a variety of wildlife including Asian elephants, critically endangered tigers, and over 350 species of birds. However, the area faces significant environmental challenges due to human activities such as poaching, illegal logging, and unsustainable harvesting practices.
Conservation efforts are ongoing, with five protected areas established to help safeguard the ecosystem. Nonetheless, issues such as political instability and climate change pose additional threats, including habitat fragmentation and changes in water availability stemming from the melting Himalayan glaciers. Overall, the Irrawaddy Moist Deciduous Forests represent a vital yet vulnerable ecosystem that requires attention to ensure its sustainability and biodiversity.
Irrawaddy moist deciduous forests
Category: Forest Biomes.
Geographic Location: Southeast Asia.
Summary: Although this region is fairly rich in biodiversity and has a moderate number of endemic species, it suffers from inadequate management of resources, which poses a serious threat to its future.
Found in the central areas of the Southeast Asian country of Burma (Myanmar), the Irrawaddy Moist Deciduous Forests biome covers an area of 53,400 square miles (138,300 square kilometers). Due to its remote geographical location, limited access, rugged landscape, and political instability, this area remains one of the least explored and scientifically studied ecoregions of the world. This ecosystem can be classified under both tropical and subtropical moist broadleaf forests zones that are found on well-drained hilly slopes or undulating lands located above 3,000 feet (1,000 meters) in elevation.
The Irrawaddy is the 10th-largest river in the world in terms of water discharge, and the most important commercial waterway of Burma. Geographically, the ecoregion is located within the Irrawaddy river basin and its major tributaries: the Chindwin, Salween, and Sittang rivers. It extends over the catchments of Bago Yoma and the foothills of Rakhine Yoma. Notably, all these rivers originate in the north, run more or less southward almost parallel to one another, before emptying into the Gulf of Martaban and the Andaman Sea.
Nearly the whole of Burma lies within the tropics; therefore, the country enjoys a tropical climate characterized by rain-bearing southwest monsoon winds. However, the north-to-south orientation of its hills and mountains brings about some minor, isolated climatic differences. Burma has three seasons. The cold season runs October through February, with average temperatures of 68–75 degrees F (20–24 degrees C). The hot season, March through May, features average temperatures of 86–95 degrees F (30–35 degrees C). The wet season, running June through September, sees average temperatures of 77–86 degrees F (25–30 degrees C). The ecoregion lies within a dry belt where the average annual rainfall is approximately 59 inches (150 centimeters), interrupted by frequent dry spells.
Biota
The climatic conditions and the soil composition of this area support the growth of closed high forest. Canopies often reach a height of up to 120 feet (37 meters). Teak (Tectonia grandis) and pyinkado or ironwood (Xylia kerri) are the most important canopy species of the biome, and are leading items of export, promoting Burma to considerable economic importance. In addition, the Irrawaddy Moist Deciduous Forests region is home to bamboo groves and some key evergreen species: Berrya ammonilla, Ginelina arborea, Homalium tomentosum, Lannea grandis, Millettia pendula, Mitravgyna rotundifolia, Odina wodia, Pterocarpus macrocarpus, Salmalia insigni, Terminalia belerica, T. pyrifolia and T. tormentosa.
In the lower Burma region, the common bamboo species are Bambusa polymorpha and Cephalostachyum pergracile; in the north, Dendrocalamus hamiltonii, D. membranaceus, and Cephalostachyum pergracile are common species of bamboo. The dominant undergrowth of these forests includes Leea spp., Barleria strigosa, and the family Acanthaceae, a taxon of flowering plants. Importantly, when extraction of timber leaves gaps in the forest canopy, the cleared areas often become hubs of the harmful invasive weed Eupatorium odoratum.
The ecoregion harbors a number of large animals. Asian elephants (Elephas maximus) are geographically widespread here—but their numbers have declined in recent years due to large-scale poaching and smuggling of ivory and skin, especially into Thailand. Tigers (Panthera tigris), quite common species until the turn of the century, are now critically endangered. A survey of the area conducted by One Earth did not confirm the presence of tigers. Eld's deer (Cervus eldi) are also endangered.
Other characteristic fauna—now found most readily in the national parks—are the gaur (Bos gaurus), sambar (Cervus unicolor), serow (Capricornis sumatrensis), golden cat (Felix temmincki), masked palm civet (Paguma larvata), marbled cat (Felis marmorata), leopard cat (Felis bengalensis), spotted linsang (Prionodon pardicolor), Himalayan black bear (Selenarctos thibetanus), Himalayan sun bear (Helarctos malayanus), binturong (Arctictis binturong), dhole (Cuon alpinus), and capped langur (Presbytis pileatus).
The biome remains home to 350 species of forest and waterbirds. Recent research unfolds that the white-throated babbler (Turdoides gularis), belonging to the family Timaliidae, is the single near-endemic bird species of the region; it is found in few if any other places. Other species of forest birds common to the region are woodpecker, laughing thrush, babbler, oriole, drongo, parakeet, barbet, pigeon, dove, and magpie. Waterbirds found in the Irrawaddy include red-wattled lapwing (Vanellus indicus), wagtail, sandpiper, forktail, and river chat (Thamnolacea leucocephala).
Five protected areas, with a total area of 1,700 square miles (4,420 square kilometers), have been delineated within this ecoregion: Pego Yoma, Alaungdaw Kathapa, Shwesettaw, Kyatthin, and Minwun Taung.
The region is moderately rich in mineral resources; precious stones such as ruby, sapphire, and amber are mined in Chindwin and the Irrawaddy valley.
Human Impact
Despite increasing concerns about overarching threats such as political instability, poaching, illegal logging, cutting trees for fuelwood and fodder, unsustainable harvesting, and unsound mining practices—and despite local and international efforts to find solutions to these problems—the region continues to suffer from environmental threats. As a consequence, local authorities have turned to the idea of establishing more protected areas and new methods of forest management, in the hope of making the area economically sustainable while maintaining the biodiversity. However, public indifference remains a problem. Insufficient financial resources, lack of community education, and scant enforcement continue to contribute to inadequate environmental management of the region.
On a global level, climate change is already effecting the Irrawaddy drainage basin, as much of the water source here is from the melting Himalayan glaciers. Due to this accelerated melt, increases in water discharge are expected initially—along with the risks of flooding and landslides—to be followed later by seasonal water shortages and limited water supplies for downstream communities. Habitat fragmentation from these forces looms as a major threat to the Irrawaddy Moist Deciduous Forests biome.
Bibliography
Adams, William M. Green Development: Environment and Sustainability in the Third World, 2nd Ed. London: Routledge, 2001.
Clarke, J. E. “Biodiversity and Protected Areas—Myanmar.” Mekong River Commission, 2011. http://www.mekonginfo.org/assets/midocs/0002035-environment-biodiversity-and-protected-areas-myanmar.pdf.
Schueman, Lindsey Jean. "Asian Elephants: Highly Intelligent Caretakers of the Southeast Jungle." One Earth, 12 Apr. 2022, https://www.oneearth.org/species-of-the-week-asian-elephant/. Accessed 22 Aug. 2022.
Water Resources eAtlas. “Watersheds of Asia and Oceania.” http://pdf.wri.org/watersheds‗2003/as13.pdf.
Xu, Jianchu, et al. “The Melting Himalayas: Cascading Effects of Climate Change on Water, Biodiversity, and Livelihoods.” Conservation Biology 23, no. 3 (2009).