Going Way Out On A Limb.(Directory)

Solitude and seclusion are no longer easy to find, even in the wilderness. In Europe and the United States, camping has taken off in the last few years, causing overcrowding at some of the world's most popular destinations. A recent study by the U.S. Sporting Goods Manufacturers Association found a 16 percent increase in the number of tent campers since 1993. In France, the Netherlands, Italy and Spain, rental-car companies have started running out of RVs; Camping Cheque, a popular France-based company that sells discounted pitch fees in the low-season months, has seen business grow from 10,000 to 1 million clients in the last five years. In response, upscale adventurers are seeking out new highs in the trees and new lows deep in caves to escape the crowds.

HIGHS: "Our treehouses are discreetly tucked away in the forest, in the boughs of ancient mahogany trees," says Trevor Saxty, president of California-based Adventure Center (adventurecenter.com), which offers camping excursions throughout Africa. For $275 per night, tourists can sleep in a timber treehouse overlooking Tanzania's Lake Manyara National Park, famous for its tree-climbing lions (not to worry: they climb only acacia, not mahogany trees).

In 1996, inspired by a class on human-environmental relations, Hawaii- based architect Dave Greenberg designed four tree houses near Hana, Maui. Two years later, he expanded his business to the island of Hainan, in the South China Sea (treehousesofhawaii.com; 86-1380-7500- 909). The result is a small group of secluded cabins overlooking some of the world's most pristine beaches. On Hainan, the houses perch in tamarind trees that sprout from --a sand dune. They overlook a beach and adjoin ...