In 1973, 55.8 million hectares (76%), of Borneo was old-growth rainforest. About 19.5 million ha of old-growth forest area was destroyed between 1973 and 2016 by fire and agricultural expansion. By 2016, 50% of the island remained forested.
See also the atlas of deforestation and industrial plantations in Borneo:
Center for International Forestry Research (CIFOR)