The Kaserdoh (Big Mountain) Wildlife Sanctuary, "a unique combination of riperian forest, extensive mineral springs, and high-altitude montane forest" and "one of the greatest natural areas left in Indochina," was designated to protect the habitat of the Sumatran rhinoceros (a species declared "almost certainly extinct" by the World Conservation Union in 1982), the tiger, tapir, clouded leopard, and other vulnerable or endangered species, as well as the headwaters of three large tributaries of the Tenasserim. Kaserdoh forms part of the "Kayah-Karen/Tenasserim Moist Forest" habitat that the World Wildlife Federation considers to be one of the world's 136 most threatened terrestrial ecosystems.

The proposed Myinmoletkat Nature Reserve covers Kaserdoh. According to a declaration by the Karen National Union (KNU) in January 1997: "the KNU does not recognize the superimpostition of biosphere reserves or wildlife sanctuaries by the SLORC (State Law and Order Restoration Council) or foreign companies whose intentions are questionable, dishonest, and only face-saving, and those actions are devious and oppressive toward the Karen people and the proper aims and methods of ecosystem management."