Montane forests

Cool forests

Covering 7% of central Borneo, montane forests receive more rainfall than lowland forests. There, vegetation ‘strips’ water from passing clouds, which accumulates in mosses and other epiphytes. As a result, montane forests are much cooler and moister than forests in the lowlands.¹

Montane forests, reaching for the top

Montane forests swathe the Borneo highlands from approximately 1,000 m to 3,300 m (Mt Kinabalu, Sabah).²  At the higher end of this range, forests are dominated by oaks (Quercus species) and laurels (Lauraceae family), while rhododendrons (belonging to family Ericaceae) and pitcher plants are more readily observed.

At their highest altitudinal limits, montane forests are covered by moss-draped bushes and epiphytes (orchids, ferns, moss, lichen, and liverworts) abound. In general, the higher the altitude, the lower the canopy height.³

Wildlife of the highlands

Fewer species of plants and animals are found in the montane forests compared to the lowland rainforests that surround them.⁴  This is because animals in montane regions face adverse climate, lack of shelter and food shortages.

For example, on Gunung Mulu in Sarawak, of the 171 bird species found on its lowland slopes, the range of most species does not exceed 900 m. At the boundary of the upper montane region at 1,300 m, only 12 species are still found.⁵

Prominent montane birds include laughing-thrushes and the treepie. Twenty-one near-endemic and 2 endemic bird species are found in these forests. These include 2 threatened species, the blue-banded kingfisher (Alcedo euryzona) and the migratory fairy pitta (Pitta nympha).

More than 150 mammal species live in Borneo’s montane forests, making these the most species-rich for similar forests in the Indo-Pacific region.⁶ Eighteen mammals have adapted to montane forests to such a degree that they are found nowhere else on the island, including various squirrels, tree shrews and rats. Of these, 13 are threatened.

Orangutans (Pongo pygmaeus species), gibbbons (Hylobatidae family), langurs ( species), gibbons (Colobinae subfamily) and macaques (Macaca species) are found in both lowland and montane forests. Undisturbed areas can even support such large mammals as the endangered Sumatran rhinoceros (Dicerorhinus sumatrensis).⁷

Threats

Of the original 2,270,000 ha of montane forests, 1.6 million ha remained in 2002 - a reduction of 30% of the original size.⁸

There are significant threats from planned mining operations, large dams, and conversion to agriculture and high-altitude timber plantations. Illegal collection of species for the commercial trade and shifting cultivation are also on the rise, threatening the integrity of Borneo's highly distinctive montane biodiversity.⁹