A green group is calling on conservation officials to plug loopholes in protection measures for ecologically sensitive areas in Tuen Mun and South Lantau.
The call from the Conservancy Association comes after it conducted studies of the Shui Hau Wan mudflat on Lantau and the Lung Kwu Tan valley in Tuen Mun.
It found that the mudflat near Tong Fuk, a popular site for clam-digging and a breeding ground for horseshoe crabs, was not covered by a zoning plan covering the wider area. And even if it had been covered by the plan, its protection would be minimal.
"When you look at the land-use zoning map, the Tong Fuk area is covered with an outline zoning plan," the association's senior campaign manager, Peter Li Siu-man, said. "But unfortunately, this is an unenforceable plan, since it was not preceded by a so-called draft development permission area plan."
Measures to protect the areas have come under the spotlight after the Agriculture, Fisheries and Conservation Department voiced hesitation over its proposal in 2009 to designate the mudflat a site of special scientific interest. It cited local villagers' reservations.
The Lung Kwu Tan valley in Tuen Mun was designated a site of special scientific interest in 2012.
But Li said this status offered only "minimal" and "administrative" protection.
The site behind Lung Kwu Tan village has more than 130 species of butterfly and a rich fung shui woodland.
"The site status is an inferior one as it does not have any legal backing since it is not reflected in any enforceable land-use zoning at all," Li said.
The association also found that the valley's surroundings had suffered various degrees of disturbance and destruction such as vegetation removal and dumping of construction waste.
The Planning Department said it would draft plans for areas with high conservation value and for areas facing development threats.
The Agriculture, Fisheries and Conservation Department has identified 67 sites of scientific interest. But Li said some of these, like Lung Kwu Tan, did not have any statutory zoning protection.