Leuser Ecosystem was formally recognized in national spatial planning legislation as being of national strategic importance for environmental protection. Te smaller Gunung Leuser Na- tional Park, at the core of the Leuser Ecosystem, has also been internationally recognized for its rich ecosystems and biologi- cal diversity. It was designated as the Gunung Leuser Man and Biosphere Reserve in 1981, and in 2004, along with Kerinci Se- blat National Park and Bukit Barisan Selatan National Park, was declared part of a ‘cluster’ World Heritage Site known as the Tropical Rainforest Heritage of Sumatra.
Along with species level and area specific conservation legisla- tion, there are also numerous other environmental regulations and planning guidelines designed to protect the environment. Tese include protection of forests on steep slopes and those above
2,000 m asl, certain sensitive soil types, including deep peat, buffer zones along river banks and around other water sources, and the upper reaches of water catchment areas (Map 19).
Extensive land use suitability studies were carried out in the 1980s and 1990s, using many of these criteria. Te results show that only 1.3% of the current orangutan distribution area is actually suitable for agricultural development, and only 10.7% would be suitable with significant inputs (such as irrigation and fertilizers) (Map 20).
To further limit damage in critical areas, comprehensive and detailed environmental impact assessments were made a com- pulsory pre-requisite for all large scale development activities in 1999. In addition, the Government of Indonesia has made