Such forests cover about 10% of the total land area of Sarawak, but have mostly been exploited for timber and plantation agriculture.

The Maludam National Park encompasses the largest single patch of peat swamp forest remaining in Sarawak and Brunei.

Maludam National Park also has the only viable population of the red banded langur (Presbytis chrysomelas cruciger) remaining in the world today.

Maludam National Park also has one of only about five viable populations of proboscis monkey (Nasalis larvatus) in Sarawak.

Diversity of other mammals is low, but there are numerous birds in the park, including black, Oriental pied and rhinoceros hornbills, blue-eared and stork-billed kingfishers, green imperial pigeon, slender-billed crow, greater racket-tailed drongo and, occasionally, the rare Storm's stork.