Brahmaputra Valley semi-evergreen forests
The Brahmaputra Valley semi-evergreen forests, located in South Asia, are a significant ecoregion rich in biodiversity, situated along the alluvial plains of the upper Brahmaputra River. These tropical moist broadleaf forests span approximately 21,892 square miles (56,700 square kilometers) and are primarily found in Assam, extending into Arunachal Pradesh, Nagaland, and Bhutan. The region benefits from fertile soils, nourished by the Brahmaputra River and its tributaries, which support a diverse array of flora, including flowering evergreen plants and various bamboo species.
Despite their ecological importance, these forests face threats from human activities such as agriculture, livestock grazing, and climate change, leading to habitat fragmentation and loss. The area is home to many endangered species, including the golden langur, Indian rhinoceros, and the South Ganges river dolphin, highlighting its role as a critical habitat for wildlife. The forests also provide essential ecological services, including soil retention and carbon sequestration, which are vital for climate regulation.
With climate change increasing in severity, the region is becoming increasingly vulnerable, necessitating the implementation of conservation strategies and sustainable land management practices to protect both the unique ecosystems and the livelihoods of the communities that depend on them.
Brahmaputra Valley semi-evergreen forests
- Category: Forest Biomes.
- Geography Location: South Asia.
- Summary: The Brahmaputra Valley's semi-evergreen forests are rich in species, but following exploitation by anthropogenic activities such as agriculture, fire clearing, livestock grazing, and tea plantation, the habitats are threatened by climate change.
The Brahmaputra Valley semi-evergreen forests are one of the two hundred global ecoregions in India, supporting significant biological diversity even after many years of forest degradation. They lie in the foothills of the eastern Himalayas along the alluvial plains of the upper Brahmaputra River. The region can be characterized as tropical moist broadleaf forests covering an area of 21,892 square miles (56,700 square kilometers). It is situated in the eastern state of Assam, stretching to the neighboring states of Arunachal Pradesh, Nagaland, and southern reaches of the country of Bhutan. The plains of the valley are highly fertile, as the mighty Brahmaputra River (itself a main tributary of the Ganges) supports the formation of rich soils by bringing sediments from the Himalaya mountains, its point of origin. Two other rivers, Manas and Subansiri, add water to these plains. The vegetation experiences 59 to 118 inches (150 to 300 centimeters) of rainfall from June to September; local variances are generated in part by elevation.
The forests of the Brahmaputra Valley are inextricably associated with the welfare of millions of people and the rich biota here. The forests not only provide goods, but also support ecological services such as soil retention, carbon sequestration, climate regulation, and habitat for a wide range of flora and fauna. Under pressure from growing population, migration, and economic development, this biome has sustained fragmentation of its ecosystems.
Floral Biodiversity
The forest types here include such flowering evergreen plants as the genus Syzygium in the myrtle family, the Cinnamonium genus of the laurel family, the jackfruit or breadfruit family Artocarpus, and the family Magnoliaceae. Deciduous vegetation here includes such regionally common trees as the hardwood Terminailia genus, favoring riverine areas but also known to thrive in drier zones, and the typical Asian rainforest species Tetrameles nudiflora. Bamboo species such as spiny bamboo (Bambusa arundinaria) and giant bamboo (Dendrocalamus hamiltonii) also grow on the alluvial plains. The original forest types, however, occur mainly in patchwork; much has been lost because of the slash-and-burn agricultural practices employed here. Many areas of previous forest cover have been converted to grasslands by the high level of human influence. The grasslands along the Brahmaputra River often have soft and muddy soils; these wet grasslands provide habitat for such animals as the hispid hare (Caprolagus hispidus) and pygmy hog (Porcula salvania).
Faunal Biodiversity
The ecoregion has a significant percentage of unique animal species, and is targeted by the Convention on Biological Diversity to reduce the loss of biodiversity by encouraging conservation practices. The area supports various threatened large mammal species such as the tiger (Panthera tigris), Asiatic elephant (Elephas maximus), greater one-horned rhinoceros (Rhinoceros unicornis), gaur or Indian bison (Bos gaurus), clouded leopard (Pardofelis nebulosa), sloth bear (Melursus ursinus), and Asiatic black bear (Ursus thibetanus).
A hallmark monkey species here is the golden langur (Trachypithecus geei), restricted to the patch of semi-evergreen and tropical forest on the northern bank of the Brahmaputra River between where the Sankosh and Manas Rivers descend from the mountains. The Brahmaputra River here is host to the South Ganges river dolphin (Platanista gangetica gangetica), a freshwater type that is endangered; it is known as the only type of cetacean to swim on its side.
The biome is a favorite place for 370 species of birds, two of which are near-endemic (found exclusively in this biome): the marsh babbler (Pellomeum palustre) and the manipur bush quail (Perdicula manipurensis). The International Council for Bird Preservation has designated the Assam Plains an Endemic Bird Area, making it one of twelve Endemic Bird Areas in India. The overlapping Brahmaputra Valley semi-evergreen forests contain three restricted-range bird species. The endangered Bengal florican (Houbaropsis bengalensis) is also found here, strictly limited to protected areas. It has been reported that any damage or conversion of grasslands supporting the species could lead to its extinction.
Protected Areas and Threats
The ecoregion has twelve protected areas, the largest of which are Manas, Dibru–Saikowa, Kaziranga, and Mehao. Mehao is distributed between two ecoregions and falls into International Union for Conservation of Nature (IUCN) Category IV. The Kaziranga National Park is the largest protected area for the Indian rhinoceros, but seeks additional protection support to strengthen the security of the species.
The Brahmaputra Valley semi-evergreen forests are one of the eastern Himalayan hot spots of biodiversity. The Himalayan region has shown consistent warming trends during the past one hundred years, with some research showing a higher-than-global-average increase rate here. It has further been recorded that the higher elevations of the Tibetan plateau are sustaining higher-than-average temperature increases. These warming trends bring with them glacier loss, earlier snowmelt patterns, alterations in water flow and sediment deposition, and thus the likelihood of multiplying impact on habitats downstream and at all elevations. The region is considered highly vulnerable to climate change and continued increases in temperature in the area are expected. Further, the combination of altered water flows combined with climate caused changes in weather patterns threaten the area with increased risks of flooding.
The Brahmaputra Valley ecoregion has already suffered considerable degradation of its forests due to land-use and land-cover changes, which in turn feed back into local and regional climate change impacts. The forests have a strong and complex role in regulating weather patterns; disruption of forest carbon cycle roles can add to temperature rise, shift rainfall patterns, and undermine the integrity of various habitats. The ultimate result is stress on the biota, and potential loss of species diversity.
Human communities also face myriad challenges in maintaining sustainable cultivation practices because of the modern crisis of urban development. The secondary forest lands of the ecoregion need climate-change mitigation practices such as community-based forest management and joint forest management. The measures required to respond to the changing climate include enhanced farming blending both contemporary techniques and traditional knowledge; conservation ethics applied at the local community and broad landscape levels; and input, support, and enforcement from regional, national, and international governments, scientists, and nongovernmental institutions.
Bibliography
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