section_path: Ecology and environment
section_name: Ecology and environment
paragraph_text: Ecology and environment
  
  Human development, mostly agriculture, has replaced nearly all of the original natural vegetation of the Ganges basin. More than 95% of the upper Gangetic Plain has been degraded or converted to agriculture or urban areas. Only one large block of relatively intact habitat remains, running along the Himalayan foothills and including Rajaji National Park, Jim Corbett National Park, and Dudhwa National Park. As recently as the 16th and 17th centuries the upper Gangetic Plain harboured impressive populations of wild Asian elephants (Elephas maximus), Bengal tigers (Panthera t. tigris), Indian rhinoceros (Rhinoceros unicornis), gaurs (Bos gaurus), barasinghas (Rucervus duvaucelii), sloth bears (Melursus ursinus) and Indian lions (Panthera leo leo). In the 21st century there are few large wild animals, mostly deer, wild boars, wildcats, and small numbers of Indian wolves, golden jackals, and red and Bengal foxes. Bengal tigers survive only in the Sundarbans area of the Ganges Delta. The Sundarbands freshwater swamp ecoregion, however, is nearly extinct. The Sundarbans mangroves (Heritiera fomes) also grow in the Sundarbans area of the Ganges Delta. Threatened mammals in the upper Gangetic Plain include the tiger, elephant, sloth bear, and four-horned antelope (Tetracerus quadricornis).
  
  Many types of birds are found throughout the basin, such as myna, Psittacula parakeets, crows, kites, partridges, and fowls. Ducks and snipes migrate across the Himalayas during the winter, attracted in large numbers to wetland areas. There are no endemic birds in the upper Gangetic Plain. The great Indian bustard (Ardeotis nigriceps) and lesser florican (Sypheotides indicus) are considered globally threatened.
  
  The natural forest of the upper Gangetic Plain has been so thoroughly eliminated it is difficult to assign a natural vegetation type with certainty. There are a few small patches of forest left, and they suggest that much of the upper plains may have supported a tropical moist deciduous forest with sal (Shorea robusta) as a climax species.
  
  A similar situation is found in the lower Gangetic Plain, which includes the lower Brahmaputra River. The lower plains contain more open forests, which tend to be dominated by Bombax ceiba in association with Albizzia procera, Duabanga grandiflora, and Sterculia vilosa. There are early seral forest communities that would eventually become dominated by the climax species sal (Shorea robusta) if forest succession was allowed to proceed. In most places forests fail to reach climax conditions due to human causes. The forests of the lower Gangetic Plain, despite thousands of years of human settlement, remained largely intact until the early 20th century. Today only about 3% of the ecoregion is under natural forest and only one large block, south of Varanasi, remains. There are over forty protected areas in the ecoregion, but over half of these are less than 100 square kilometres (39 sq mi). The fauna of the lower Gangetic Plain is similar to the upper plains, with the addition of a number of other species such as the smooth-coated otter (Lutrogale perspicillata) and the large Indian civet (Viverra zibetha).