Making scents: saviours of the incense tree

Ho Pui-han makes her way along the fringes of a country path, through a patch of trampled undergrowth and then points to a deep gash at the base of a tree.

"You can see where they've cut the wood as a test," says the conservationist. "They'll be back in a month to check and, if it's the right tree, they'll just chop it down and carry it across the border."

Close to extinction in the mainland and internationally protected as a species, Hong Kong's dwindling stands of , commonly called the incense tree, have become a holy grail for smugglers. The tree's resin, which gives off a heady scent - like a muskier, more complex sandalwood - has been prized as a spiritual and medicinal tool for centuries throughout the Eastern world, and continues to star in high-end perfumes and expensive incense. The resin has always been rare - only mature trees can produce it naturally and only then when they have been infected with mould or injured - but an international-protection ruling in the 1990s has seen its value soar. At its most potent, the resinous wood can fetch more than HK$12,000 per gram on the mainland market.

The lucrative nature of the industry was highlighted in December, when customs officers in Macau caught a group trying to smuggle nearly US$3 million worth of incense timber (known commonly as agarwood) into the mainland. In Hong Kong, hikers and villagers have increasingly been reporting signs of illegal harvesting, among them makeshift camps and sightings of what they believe to be gangs of harvesters from across the border.

"They can do it so fast, so quickly," says Ho, who has been tracking the handiwork of tree poachers for the past few years. "They can travel to Hong Kong easily, legally, and they go hiking. And the AFCD [Agriculture, Fisheries and Conservation Department] always tells me, 'We don't have adequate people to inspect the places.' But Hong Kong has a vast countryside and this is not good enough."

"Most of the bigger trees have already been stolen," Jim Chi-yung, a tree expert and professor of geography at the University of Hong Kong, told the last year. "The poaching is very serious. With the larger trees gone, the poachers are beginning to move to the lesser trees."

Just a few kilometres from Hong Kong's border with the mainland, Ho leads us further into Pat Sin Leng Country Park, pointing out stumps and marked trunks (when a cut is made, a suitable tree will start secreting resin). She offers eco-tours regularly, with the help of a few other volunteers, hoping to raise awareness of forest crimes. Ho says reports now come in weekly.