Then, in 1950, everything began to change. A popular revolt by the people of Nepal brought about the collapse of the Rana regime, and with it the end of the big hunts. In the hills the economic situation had been deteriorating for several decades. The population grew so fast that people ran out of land on which to grow crops. In desperation, the land-hungry farmers began to venture down into the plains, the new government felt obliged to open Chitwan for settlement.
An agricultural development program was started and thousands of hill people poured into the valley in search of land. A malaria-eradication scheme, launched by the Government and the United States Agency for International Development (USAID) in 1954 proved so successful that the whole district was declared malaria-free in 1960.

All this was progress of a kind. But the human influx was so vast and so rapid that inevitably it had a disastrous effect on the wildlife habitat. Poaching became rampant, and little was done to control it. The main target was rhino, whose horn - renowned for its alleged medicinal properties - already commanded enormous prices in the drugstores of the East.
By the end of the 1950s it was clear that if such a decline continued, the rhino and other animals would soon face extinction. Already the swamp deer and the water buffalo had almost disappeared from Chitwan. Therefore, in 1959, the Fauna Preservation Society appointed the distinguished British naturalist E. P. Gee to make a survey. Gee, who had spent most of his life in India and was an authority on its wildlife, recommended the creation of a national park north of the Rapti river, and this was duly established in 1961. He also proposed a wildlife sanctuary to the south of the river for a trial period of ten years. After he had surveyed Chitwan again in 1963, this time both the Fauna Preservation Society and the International Union for the Conservation of Nature, he recommended an extension of the national park to include areas of rhino country in the south.

In 1963 a government committee investigated the legal status of immigrants in the Chitwan valley; the Land Settlement Commission of 1964 resettled 22,000 people, including 4,000 from inside the rhino sanctuary, elsewhere in the valley. Drastic though it was, the operation brought little immediate improvement, for the people who had been evicted poured back into the area to collect firewood and fodder; the habitat deteriorated still further, and the rhino population continued to decline. A survey carried out in June 1968 estimated that only a total of between eighty-one and 108 rhinos were left. The report, published in 1969, predicted that unless total protection were afforded, the rhino would disappear by 1980.
In December 1970, His late Majesty King Mahendra approved the establishment of the national park south of the Rapti river. The boundaries were delineated in March and April of 1971, and preliminary development began in October that year. Royal Chitwan National Park was officially gazetted in 1973 by His Majesty King Birendra and became the first national park in Nepal