Orangutan viewing in Bukit Lawang, one of the main orangutan tourism locations (Perry van Duijnhoven)
or on elephants (Gunung Leuser National Park 2010). Exist- ing and future tourism activities during which orangutans can be viewed are recommended to follow strict guidelines (Macfie and Williamson 2010) to reduce disease risk.
Tere are additional tourism opportunities linked to the Su- matran orangutan that remain unexploited (Gubler 2006). Te rivers, swamps and villages in the Tripa, Kluet and Sing- kil areas offer great ecotourism potential due to the spectacu- lar landscape and friendly inhabitants. Tese could easily be combined with initiatives to develop tourism on the nearby Banyak Islands, where tourism development is largely related to sea turtles.
Non-timber-forest products and biodiversity People collect a wide variety of non-timber-forest products (NTFP) from the forests where orangutans occur in Suma- tra. Tese range from animal products such as honey and the highly prized nests made from the hardened saliva of the edible-nest swiftlet (Aerodramus fuciphagus) to plant products such as a rattan species (Calamus manan) used to make fur- niture (Wind 1996; van Beukering et al. 2001). When the forests are lost the opportunities to collect these items is naturally reduced.
Biodiversity in an area is often reflected in the value of tourism (treated above), but it can also be important for the potential value of pharmaceutical sources and funds from international organisations aiming to conserve biodiversity.
Te ecosystem services list that is included for valuation in this report (see below) is not exhaustive and several other impor- tant ecosystem services are provided by the forest areas where
Bee nests used for honey collection hanging high up in the canopy of a large tree (Perry van Duijnhoven)
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orangutans occur, such as regulation of local climate, hunting, harvesting of non-timber forest products that were not includ- ed in the van Beukering study (such as camphor trees, Dry- obalanops aromatica), used for centuries for culinary and me-