Northern Triangle subtropical forests

Content Cover Image

Malikha River, Northern Kachin State. By Tha (Own work) [CC-BY-SA-3.0 (], via Wikimedia Commons


The Northern Triangle Subtropical Forests are one of the least explored and scientifically known places in the world. The region's remote location, limited access, and rugged landscape have kept scientific exploration at a minimum. Yet what is known about these forests still ranks them as globally outstanding in their biological diversity. There are at sixty-five endemic mammals known from this ecoregion, but more probably await discovery. In 1997 a new species of small deer, the leaf muntjac, was discovered high in the mountains. This ecoregion remains one of the few places in the Indo-Pacific region where conservation action can be done on a proactive rather than reactive basis.

Location and General Description

Floristically, Kachin State in northern Myanmar is one of the most diverse regions in continental Asia , but it is also one of the least explored. In 1997 a WCS team went into the region, the first in more than fifty years, since the early explorations of Kingdon-Ward (1921, 1930, 1952). Therefore, our assessment of the biodiversity in this region probably is highly underestimated; it probably harbors many more species than are now attributed to it.

caption WWF

The mountains trace their origins to the geological period when the collision between the Deccan Plateau and the Laurasian mainland created the Himalayas. The mountains extend as offshoots from the eastern Himalayas in four parallel ranges. The westernmost Sangpang Bum Range forms the Indo-Myanmar boundary, and the easternmost Goligong (Gaoligong) Shan demarcates the Myanmar-China border. In general, the elevation exceeds 1,500 meters (m), but the peaks rise steeply to more than 3,000 m. The Chindwin, Mali Hka, and Mai Hka rivers originate in these mountains and converge in the lower reaches to form the Irrawaddy River.

The varied topography and biogeographic setting at the crossroads of the Assam-Indian, Eastern Himalayan, Indo-Malayan, and Chinese flora, as well as the ancient Gondwana relicts that have taken refuge here, give the ecoregion a high floral diversity. However, the Pleistocene glaciation has influenced the distributions of these floras. The Indo-Malayan elements are now limited to the river valleys, below 2,400 m, with the Indo-Himalayan flora stratified above.

This ecoregion consists primarily of the large area of subtropical broadleaf forest but includes small, sub-regional-scale patches of temperate broadleaf forests and sub-alpine conifer forests. The subtropical forests are distributed roughly between 500 and 1,600 m. Magnoliaceae, Lauraceae, and Dipterocarpaceae species make up the associations below 915 m, and species of Fagaceae, Meliaceae, tree ferns, and climbing palms make up the upper-elevation associations. Characteristic trees in these forests include Acer pinnatinervium, Aesculus assamicus, Betula alnoides, Carpinus viminea, Castanopsis argentea, Magnolia pterocarpa, Persea spp., Litsea spp., and Lindera spp. In mature forests the trees are draped with lianas (Jasminum duclouxii, J. pericallianthum, Lonicera hildebrandii, Bauhinia spp., Clematis spp., Mussaenda spp., and Rubus spp.). Along the upper limits (above 1,525 m) the forest is dominated by Bucklandia populnea.

The Ngawchang valley, at 1,000 and 1,980 m between Htawgaw and Gangfang in the western part of the ecoregion, has a pine-oak association that is characterized by Pinus kesiya, Quercus incana, Q. serrata, and Q. griffithii. A rich, unique herb flora of Anemone begoniifolia, Gentiana cephalantha, Gerbera piloselloides, Inula cappa, Lilium bakerianum, L. ochraceum, Primula denticulata, and Senecio densiflora grows in these open forests, considered a fire-maintained preclimax community.

Several endemic species are associated with these forests, including the terrestrial orchid Paphiopedilium wardii and other endemics such as Agapetes adenobotrys, A. pubiflora, Brachytome wardii, Lactuca gracilipetiolata, Lasianthus wardii, Paphiopedilum wardii, and Strobilanthes stramineus.

Biodiversity Features

The ecoregion harbors almost 140 mammal species, including three near-endemic species and six endemic species (Table 1). One of the endemic species, Muntiacus putaoensis, was discovered in 1997 during the most recent scientific trek into the region.

Table 1. Endemic and Near-Endemic Mammal Species.
Family Species
Talpidae Talpa grandis*
Talpidae Scaptonyx fusicauda*
Soricidae Chimarrogale styani*
Vespertilionidae Pipistrellus anthonyi*
Cervidae Muntiacus gongshanensis
Sciuridae Sciurotamias davidianus*
Sciuridae Callosciurus quinquestri
Muridae Niviventer brahma
Cervidae Muntiacus putaoensis*
An asterisk signifies that the species' range is limited to this ecoregion.


Several threatened species that make up part of this ecoregion's mammal fauna are also of conservation importance. These species include the tiger (Panthera tigris), red panda (Ailurus fulgens), Asian elephant (Elephas maximus), takin (Budorcas taxicolor), southern serow (Naemorhedus sumatraensis), pig-tailed macaque (Macaca nemestrina), Assamese macaque (Macaca assamensis), stump-tailed macaque (Macaca arctoides), capped leaf monkey (Semnopithecus pileatus), hoolock gibbon (Hylobates hoolock), Asiatic black bear (Ursus thibetanus), great Indian civet (Viverra zibetha), clouded leopard (Pardofelis nebulosa), red goral (Naemorhedus baileyi), Irrawaddy squirrel (Callosciurus pygerythrus), and particolored squirrel (Hylopetes alboniger).

The ecoregion's large, contiguous habitat areas are included within a Tiger Conservation Unit (TCU) identified for immediate survey. Maintaining landscapes with large habitat blocks is important to conserve these large predators, and this TCU provides one of few opportunities in the region to do so.

Wolf (Canis lupus) and musk deer (Moschus moschiferous) are considered to be recently extinct in this area.

The bird fauna exceeds 370 species. There is one near-endemic species, the rusty-bellied shortwing (Brachypteryx hyperythra) (Table 2). However, there are several birds that can be considered focal species because of their need for mature forests and low thresholds for disturbance. Some of these species are Blyth's tragopan (Tragopan blythii), great hornbill (Buceros bicornis), wreathed hornbill (Aceros undulatus), and rufous-necked hornbill (Aceros mipalensis). The ecoregion overlaps with the far eastern portion of the Eastern Himalayas (130) EBA.


Table 2. Endemic and Near-Endemic Bird Species.
Family Common Name Species
Turdidae Rusty-bellied shortwing Brachypteryx hyperythra
An asterisk signifies that the species' range is limited to this ecoregion.


With Assam, this region in northern Myanmar is considered to be one of the richest in the world for Lepidoptera.

Current Status

Because of its remoteness and inaccessibility, very little of this ecoregion has been substantially altered by human activity. More than 90 percent of the habitat is still intact in large habitat blocks, but there is little formal protection. Most of the areas covered by dense forest are demarcated as reserved forests but include the Piodaung Wildlife Sanctuary (Table 3).

Table 3. WCMC (1997) Protected Areas That Overlap with the Ecoregion.
Protected Area Area (km2) IUCN Category
Piodaung 250 UA
Ecoregion numbers of protected areas that overlap with additional ecoregions are listed in brackets.


However, the forests on hill slopes are being rapidly cleared for shifting cultivation. The shifting cultivation cycle has also been reduced from twelve to twenty years to five to eight years, resulting in the perpetuation of a bamboo subclimax that has begun to replace the broadleaf forests.

Types and Severity of Threats

The continual extraction of timber in this ecoregion and the increasing demand on the black market for timber to be transported into Yunnan Province, China is a serious threat to the future biodiversity of the [[region]. This ecoregion has also become increasingly populated since 1988 as private companies have been allowed to extract gems, minerals, and timber.

Justification of Ecoregion Delineation

MacKinnon's subunit 09b includes the tropical and subtropical moist broadleaf forests in the Kachin and upper Chindwin areas of northern Myanmar. We included the tropical moist forests within the Mizoram-Manipur-Kachin Rain Forests, which then extends east across northern Myanmar, and the subtropical moist broadleaf forests of the Golden Triangle to the north in the Northern Triangle Subtropical Forests.

This region does not correspond well to Udvardy's biogeographic provinces. The Myanmar Coastal Rain Forests cover Udvardy's Burman rain forest, the southwestern portion of the Thai monsoon forest, and the western portion of the Indochinese rain forest. The Irrawaddy Moist Deciduous Forests, Irrawaddy Dry Forests, Chin Hills-Arakan Yoma Montane Rain Forests, Northeast India-Myanmar Pine Forests, Northern Triangle Subtropical Forests, and Mizoram-Manipur-Kachin Rain Forests roughly correspond to Udvardy's Burman rain forest and Burma monsoon forest.

Additional information on this ecoregion



Disclaimer: This article is taken wholly from, or contains information that was originally published by, the World Wildlife Fund. Topic editors and authors for the Encyclopedia of Earth may have edited its content or added new information. The use of information from the World Wildlife Fund should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.






Fund, W. (2014). Northern Triangle subtropical forests. Retrieved from


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