This photo taken on Jan 30, 2013 shows buffaloes (bottom) on Lantau Island in Hong Kong. (PHILIPPE LOPEZ / AFP)

HONG KONG - Construction activity on one of Hong Kong's largest islands is shrinking the habitat of its wild buffaloes, forcing them to search for food in residential areas, where barbed wire and building waste can injure them.

Grazing beneath lush country parks and Hong Kong's highest peaks, wild water buffaloes have roamed Lantau Island, 30 minutes from the glitzy finance district by ferry, since the 1970s after being abandoned by farmers taking up industrial work.

Activists estimate there are now just over 100 of them on the island

Environment activists say the buffaloes are crucial to Lantau's ecosystem, eating harmful weeds and keeping the wetlands fertile. Floating plants and microorganisms thriving on the buffaloes' presence also filter out some pollution in Lantau's rivers before they reach the sea, activists say.

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Lantau residents say encounters with the buffaloes have been unusually tense in recent months, as the animals pop up in private gardens looking for food, and sometimes even charge at people.

The angriest residents want the buffalo culled. Activists estimate the animals' numbers at just over 100, but are unsure how that compares to past years.

"There's a war happening between landowners and conservationists," said Ho Loy, an activist for the Lantau Buffalo Association.

The government's Agriculture, Fisheries and Conservation Department said that it was communicating with the community to reach "appropriate consensus" and that its cattle management focused on sterilisation and relocation.

This photo taken on Jan 30, 2013 shows buffaloes grazing in an open field on Lantau Island in Hong Kong. (PHILIPPE LOPEZ / AFP)

Land scarcity has turned densely populated Hong Kong into one of the most expensive property markets in the world, making construction lucrative, but also leading to more waste, including on Lantau's wetlands.

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Sharp objects such as broken floor tiles have become a hazard for buffaloes, causing deep cuts which can attract fly larvae and lead to infections.

Leung Siu-wah, 68, locally known as "Buffalo Jean" as she has been voluntarily looking after the buffalos for 12 years, wants the government to improve management of construction waste and do more to preserve the wetlands.

Sharp objects found among construction waste have become a hazard for buffaloes, causing deep cuts which can attract fly larvae and lead to infections

"They look for food in every nook and cranny," she said.

"When the buffaloes want to climb up to eat, they are very careless and rash ... they don’t know the waste is very sharp."

Some cuts take weeks to heal, she said.

The Civil Engineering and Development Department said it has been installing GPS on dump trucks and has issued memos to various stakeholders on their responsibilities.

"Lantau is nothing without buffaloes and wetlands," Leung said.