When was Suining called the last oasis in Asia?

Suining is located in the southwest border of Hunan Province, with a total area of 2,927 square kilometers, including 3.43 million mu of mountains, accounting for 72.95% of the county's land area. UNESCO discovered the only unpolluted oasis on the earth through the Asia-Pacific satellite in May 1982, and then located it in Suining County, China by satellite. Suining has since been hailed as a "magical oasis" by the world. Suining enjoys unique geographical and climatic conditions, with beautiful forests and forest resources in Shan Qi ranking first in Hunan Province.