Yang says that 11 of the world's 15 crane species are currently teetering on the verge of extinction, and notes that cranes, which are able to nest in a variety of environments, are an important indicator of the health of a variety of ecosystems. In Eastern cultures, cranes symbolize longevity, loyalty, and a carefree nature, in addition to representing human fantasies of and desire for Heaven.
楊恩生強調，目前全球 15 種鶴中，已有 11 種在滅絕邊緣掙扎，鶴可以在多樣化棲地中存活，是測量各種生態系健康與否的重要指標；在東方文化裡，鶴所象徵的長壽、忠貞、無憂無慮，更成為人們心中對天堂的幻想與渴望。