Bangladesh is an important transition zone between Indo-China, the Himalayas and the rest of the Indian subcontinent. Bangladesh was once rich in wildlife species. The tropical moist forests were botanically amongst the richest in the Indian subcontinent, and they also supported the greatest diversity of mammals and a high diversity of birds. The country has 113 species of mammals (out of 500 species in the Indian subcontinent), 574 species of birds (out of 1,200), 123 species of reptiles, 19 species of amphibians, 107 species of freshwater fish and 120 species of estuarine fish. Other sources put the species of mammals at 200 and species of bird at 750.
Although the species richness is relatively large for the small area of Bangladesh, endemism is low and the population size of most of the species has declined drastically. Eighteen species of wildlife are now extinct from Bangladesh. Among them are several internationally threatened species such as the three species of Asian rhinoceros, and also the banteng, nilgai, swamp deer, pink headed duck, Bengal florican and mugger crocodile.
About 5,000 species of higher plants are known from Bangladesh, a third of the number on the whole Indian subcontinent, where the main floristic affinities lie. The Chittagong area, however, has many Indo-Chinese plant species.
