About two thirds of Malaysia was covered in forest as of 2007, with some forests believed to be 130 million years old. The forests are dominated by dipterocarps. Lowland forest covers areas below , and formerly East Malaysia was covered in such rainforest, which is supported by its hot wet climate. There are around 14,500 species of flowering plants and trees. Besides rainforests, there are over  of mangroves in Malaysia, and a large amount of peat forest. At higher altitudes, oaks, chestnuts, and rhododendrons replace dipterocarps. There are an estimated 8,500 species of vascular plants in Peninsular Malaysia, with another 15,000 in the East. The forests of East Malaysia are estimated to be the habitat of around 2,000 tree species, and are one of the most biodiverse areas in the world, with 240 different species of trees every hectare. These forests host many members of the Rafflesia genus, the largest flowers in the world, with a maximum diameter of .