An endangered frog native to Hong Kong has been spotted for the first time in an ecologically rich wetland region in rural Tai Po, in the New Territories, by a local green group.“The Romer’s tree frog is a precious species only found in Hong Kong, so this is an encouraging find,” said Elaine Yuen Yan-ling, assistant education and conservation manager of local non-profit Green Power.Scientists who have been tracking the tiny frog since the 1950s, and feared at one time that it was extinct, are…