The population of the Chinese alligator began to decline in 5000 BC, when human civilization started to grow in China, after having been very abundant in the lower Yangtze area. This area was one of the first places in the world to farm rice, causing much of the alligator's habitat to be destroyed in favor of rice farms. In the 1700s, much of the Chinese alligator's habitat was replaced with farming fields after a large number of people had moved into the area. By the 20th century, its range was reduced to a few small areas around the Yangtze. In the 1950s, the alligator was in three distinct areas: the southern area of the Yangtze (Chang Jiang) from Pengze to the western shore of Lake Tai (Tai Hu), the mountainous regions of southern Anhui, and the provinces of Jiangsu and Zhejiang, primarily in lakes, streams, and marshes. By the 1970s, it was restricted to small parts of southern Anhui and Zhejiang, at which time the population was about 1,000.