Part of a network of more than 20 artificial fish ponds in Hong Kong’s Northern Metropolis development occupies government land without permission, with a green group warning that materials used at the site also threaten the area’s ecology. The ponds are near the Mai Po Nature Reserve and the Inner Deep Bay wetlands, which have been designated as internationally important under the Ramsar Convention as they are a vital habitat for migratory birds. Some of the ponds also fall within the proposed...