Overpopulation has severely strained Bangladesh's limited natural resources. Nearly all arable land is already cultivated and forestland has been greatly reduced by agricultural expansion and by timber and firewood cutting. Between 1983 and 1993, forest and woodland declined by 12.5% to 1.9 million ha (4.7 million acres). As of 1995, total forest area was only 1 million ha. Bangladesh's environmental problems have been complicated by natural disasters that add to the strain on an agricultural system which supports one of the world's most populous countries. Water supply is also a major problem because of population size, lack of purification procedures, and the spread of untreated contaminants into the usable water supply by flood waters. To ease these problems, the government has established drainage, irrigation, and flood protection systems, and has drilled thousands of tube wells to supply safe drinking water in villages. As of 2001, safe water was available to 100% of the population.
Despite passage of the Wildlife Preservation Act of 1973, wildlife continues to suffer from human encroachment. Only 0.7% of the country's total land area is protected. In 2001, 18 species of mammals, 30 species of birds and 18 plant species were considered endangered, including the Asian elephant, pygmy hog, Sumatran rhinoceros, Bengal tiger, estuarine crocodile, gavial, and river terrapin.