The Hoang Lien Son Nature Reserve was set up in 1986 to safeguard remnants of natural forest habitat over an area of thirty square kilometres south and west of Sa Pa. Over the years, trees below an altitude of 1500m have largely been cleared for agriculture, building and firewood, but reforestation programmes are under way, adding commercial timbers in an effort to reduce illegal logging....

The Hoang Lien Son Nature Reserve was set up in 1986 to safeguard remnants of natural forest habitat over an area of thirty square kilometres south and west of Sa Pa. Over the years, trees below an altitude of 1500m have largely been cleared for agriculture, building and firewood, but reforestation programmes are under way, adding commercial timbers in an effort to reduce illegal logging. Of the reserve's 56 mammal species, nearly one third are listed as rare or endangered, among them the clouded leopard, tiger and black gibbon. It's easier to spot some of the 150 bird species, a few of which are unique to the mountains of northwest Vietnam.
Vietnam's highest mountain, Fan Si Pan (3143m) lies within the reserve boundary, less than 5km as the crow flies from Sa Pa but an arduous three- to five-day round trip on foot. The usual route starts by descending 300m to cross the Muong Hoa River, and then climbs almost 2000m on overgrown paths through pine forest and bamboo thickets, before emerging on the southern ridge. The reward is a panorama encompassing the mountain ranges of northwest Vietnam, south to Son La Province and north to the peaks of Yunnan in China. Although it's a hard climb, the most difficult aspect of Fan Si Pan is its climate: even in the most favourable months of November and December it's difficult to predict a stretch of settled clear weather and many people are forced back by cloud, rain and cold. A guide is essential to trace indistinct paths, hack through bamboo and locate water sources; Hmong guides are said to know the mountain best. Sa Pa hotels and tour agents can arrange guides and porters as required (about $15 per day for each).