Sundarbans Freshwater Swamp Forests
Sundarbans Freshwater Swamp Forests, is considered to be one of the most endangered and endemic eco-regions in India, as it is nearly extinct, at present. The main reason behind this has been hundreds of years of habitation and exploitation by one of the world's densest human populations. The forests are located in the vast, productive delta of the Ganges and Brahmaputra rivers, and they are exceptionally productive due to the annual alluvial deposits made by the rivers. The brackish swamp forests lie behind the Sundarbans Mangroves where the salinity is more pronounced. The forests also lie between the upland Lower Gangetic plains moist deciduous forests and the brackish-water Sundarbans mangroves that border the Bay of Bengal. The water is slightly brackish in the Sundarbans freshwater swamp forests in India and becomes quite fresh during the rainy season. The freshwater plumes from the Ganga River and Brahmaputra rivers during rainy season and push the intruding salt water out and also bring a deposit of silt. These forests also straddle the boundary between the Indian State of West Bengal and Bangladesh, just like the vast mangrove eco region. The southwest monsoon brings heavy rain to the forests during the months of June to September and the forests also witness widespread destruction, due to frequent, devastating cyclones sweeping in from the Bay of Bengal. The annual rainfall in the forests can exceed 3,500 millimetres (mm) and the daytime temperatures can rise above 48 degrees Celsius during the monsoon months. Coupled with the humidity, the temperatures can be unbearable. The habitat in the Sundarbans freshwater swamp forests in India is so fragmented that it is quite difficult to ascertain the composition of the original vegetation of this eco-region. However, the vegetation in the freshwater swamp forests are principally characterised by the plant species like Heritiera minor, Xylocarpus molluccensis, Bruguiera conjugata, Sonneratia apetala, Avicennia officinalis, and Sonneratia caseolaris, with Pandanus tectorius, Hibiscus tiliaceus, and Nipa fruticans along the fringing banks. The forests also provide an important refuge for the Tiger, together with the mangrove eco-region.
Chhottanagpur Dry Deciduous Forest
Chhottanagpur Dry Deciduous Forest is located between the deciduous forests of the Eastern Ghats and Satpura Mountain Range and of the lower reaches of the Gangetic Plains, the Chhottanagpur dry deciduous forests in India harbour numerous flora and fauna species. The forests are home to large populations of Asia's largest predator and largest herbivore, the Tiger and the Asian Elephant. Both the animal species are still able to roam and live within the large habitat blocks of these forests that is considered as a rare phenomenon in this bio-region. The Chhota-Nagpur Plateau dry deciduous forests also have a flora and fauna that are distinct from the adjacent areas, with several pockets of endemic plants. Chhota-Nagpur Dry Deciduous Forest in India extends across the eastern Indian states of Bihar, Madhya Pradesh, and West Bengal. The plateau's ancient origin is attested to the Gondwana substrates and it is also part of the Deccan Plate. The forests in this eco region receive less rainfall compared to that of the adjacent eco regions, which support the moist deciduous forests. For this reason, the vegetation in these forests is drier than that of the adjacent eco regions. These dry deciduous forests are typically composed of three stories. The upper canopy of the forests reach 15-25 meters, the high under story reaches 10-15 meters, and the undergrowth reaches at about 3-5 meters.
The vegetation in the Chhota-Nagpur dry deciduous forests in India is primarily characterised by the species like Shorea Robusta. Habitat of this species is usually in association with the other species like Anogeissus Latifolia, Terminalia Alata, Lagerstroemia Parviflora, Pterocarpus Marsupium, Aegle Marmelos, Syzygium Operculatum, Symplocus Racemosa, and Croton Oblongifolius, etc. The Lianas are more common in the denser forests. A common habitat type in the forests is the dry deciduous scrub that grows to about 3-6 meters in height. This scrub includes the species like bamboo and shrubs like Holarrhena and Dodonaea. The Shola-type forests are located at higher altitudes and they are mainly characterised by Phoenix robusta, Pterospermum acerifolium, and Clematis nutans. The forests house a few endemic, endangered plant species like the Aglaia haselettiana, Carum villosum, and Pycnocyclea glauca, etc. Apart from these, there are also a few other plant species that are more economically useful species. These species include the Diospyros melanoxylon, Madhuca longifolia, Butea monospermous, and Shleichera oleosa, etc.
Brahmaputra Valley Semi-Evergreen Rain Forests
Brahmaputra Valley Semi-Evergreen Rain Forests in India are located in the Indian states of Assam and West Bengal. The Brahmaputra Valley semi-evergreen rain forests in India are an integral part of India's ecosystem. These forests were historically considered as one of the most productive areas in the Indian Subcontinent bio-region. This eco-region lies along the alluvial plains of the Brahmaputra River that flows through the state of Assam and West Bengal in India. The valley has been densely settled by humans and cultivated for thousands of years, because of the eco-region's high productivity. The eco-region harbours an impressive biological diversity in the small fragments of habitat that lie scattered throughout. Some of the few remaining viable populations of India like the Asian elephants and the world's largest population of the greater one-horned rhinoceros can be found in these forests.
The Brahmaputra Valley Semi-Evergreen Rain Forests in India are located along the upper Brahmaputra River plains. Though most of the forests lie within the eastern Indian state of Assam, some small sections extend into the neighbouring states of Arunachal Pradesh and Nagaland, as well. The eco-region represents the area where the northward-migrating Deccan Peninsula first made contact with the Eurasian continent during the early Tertiary period. It also represents a gateway for species exchanges between the typically Indian and Malayan faunas. There are several species that inhibit in both sides of the wide Brahmaputra River. While the species like golden Langur, hispid hare, and pygmy hog are limited to the north bank of the river, the species like hoolock gibbon and stump-tailed macaque can be found only on the south bank.
Odisha Semi-Evergreen Forests
Located on the coastal plain of the Indian state of Odisha, the Odisha semi-evergreen forests are a tropical moist broadleaf forest eco-region of eastern India. The total area of the eco region is 22,300 square kilometres and it is bounded on the north and west by the Eastern Highlands moist deciduous forests. The Bay of Bengal is bounding the eco-region on the south and west. These Odisha semi-evergreen forests are neither exceptionally species-rich nor are high in endemism. However, they do harbour several charismatic large vertebrates of the Indian Subcontinent bioregion. The most important species found in these forests include the Tiger that is considered as the region's largest predator, and also the Asian Elephant. Apart from that, large herds of Gaur, and one of the most dangerous mammals in the region, the Sloth Bear are also found in these forests.
Positioned on the low hills in the north-eastern Indian state of Odisha, the Odisha semi-evergreen forests are vulnerable to the full force of the south-western monsoon winds that sweep in from the Bay of Bengal. Due to the rainfall from this monsoon and the ameliorating year-round oceanic influences, moister climatic conditions are created here. As a result, the Orissa semi-evergreen forests in India have the original extent of distinctly moister semi-evergreen forests that once existed to the east of the Eastern Ghats Mountains. The eco-region has an ancient geological lineage of Gondwanaland origins and for this reason; it still harbours relicts of an ancient biota.
Terai-Duar Savanna and Grasslands
Terai-Duar Savanna and Grasslands is located at the base of the Himalayas, the Terai-Duar savanna and grasslands eco-region is about 25 kilometres wide. The eco-region is a continuation of the Gangetic Plain and it also stretches from southern Nepal's Terai, Bhabar, and Dun Valleys eastward to Banke. The eco-region covers the Dang and Deokhuri Valleys along the Rapti River and a small portion of it reaches into Bhutan. Each ends of the eco-region crosses the border into India's states of Uttar Pradesh and Bihar. Terai-Duar savanna and grasslands in India forms an eco-region that stretches across the middle of the Terai belt, from the state of Uttarakhand through southern Nepal to the northern part of West Bengal. As this grasslands stretch towards the eastern region, they can be counted amongst the eastern forest zone. These savanna and wetlands are actually a mosaic of tall grasslands, savannas and evergreen and deciduous forests. The grasslands are counted amongst the tallest in the world, and are well maintained by silt deposited by the yearly monsoon floods. Some of the notable grasses found in these wetlands include the Kans Grass and Baruwa Grass. The eco-region is also home to several endangered species like the Indian Rhinoceros, Elephants, Tigers, Bears, Leopards and also some other wild animals. Terai-Duar savanna and grasslands in India contain the highest densities of Tigers, Rhinos, and Ungulates in Asia. The eco region has already been included in the Global 200 and one of the features that elevate it to this list, is the diversity of ungulate species. The extremely high levels of ungulate biomass recorded in riverine grasslands and grassland-forest mosaics, is also another unique feature of this eco-region. The very tall grasslands of this eco-region are rare worldwide in comparison with short grasslands and they are also considered as the most threatened. These tall grasslands indicate that the region has mesic or wet conditions and nutrient-rich soils.