As the place closest to heaven, the Qinghai-Tibetan Plateau, also known as the roof of the world, is a paradise to such wild animals as Tibetan antelopes, wild yaks and wild Tibetan donkeys. In 1988, the Tibet Autonomous Region government drew up a series of implementation methods to protect its wild animals, following the suit of the central government's issuing of Wild Animal Protection Law. Ever since, governments at all levels in Tibet have worked hard to protect wildlife, by means of making laws and regulations, establishing nature reserves, prohibiting hunting in certain areas or in a certain period of the year, while launching publicity campaigns to popularize knowledge on wildlife protection among the general public. Related authorities also organize scientific expedition once a year for wildlife protection. Both the number of Tibetan antelopes and black-necked cranes more than doubled by 2007 to 150,000 and 6,000 respectively as compared to that in the 1990s. In 2010, the number of large and medium size animals living in Tibet topped the other Chinese provinces with the number of wild animals ranking the third in China.