believed to have moved into various parts of Japan either before 25 Mya or after 10 Mya and were extirpated from there during the Plio-Pleistocene period, due to Japan's increased isolation from the continent and harsh climate conditions. 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. In 1998, the population of the Chinese alligator was the lowest it had ever been; the largest area it lived in was a small pond along the Yangtze surrounded by farmland, which held 11 alligators. In 1999, the Wildlife Conservation Society estimated that 130–150 individuals were left in the wild. According to The New York Times, the population was less than 130 in 2001; at this time, alligators sometimes wandered around to look for a suitable habitat, but were unsuccessful due to their habitat having been turned into rice fields. In 2003, the population began to gradually increase after having been roughly stable between 1998 and 2003. A survey of the population by the Anhui National Nature Reserve for Chinese Alligator (ANNRCA) in 2005 deduced that between 92 and 114 adults and 66 young remained in the wild. The survey reasoned that the species' population was growing in four sites, but stable in the rest of the alligator's range. A 2012 journal article estimated the population at the time to be 120–150. A 2015 survey observed 64 individuals, of which 32 were adults, estimating that the total number of adults was 68–86 and