Shaping Borneo’s ecosystems

Borneo’s ecosystems are far from frozen in time. A complex combination of factors has shaped ecosystems and the biodiversity of the island; physical differences in environment, local and regional variations in climate as well as regional geological evolution.

Climate, from wet to very wet

Straddling the equator, Borneo is subject to an intense tropical climate. In the lowlands, temperatures range between 25°C and 35°C, while at higher elevations things can get a lot cooler. Borneo has 2 monsoon seasons: the “dry” monsoon (May - October) and the “wet” monsoon (November - April).

The entire island lies within what is called the ‘ever-wet zone’, receiving between 2,000mm and 4,000mm of rainfall each year.

Before Borneo became an island

During much of the Tertiary period (from around 65 to 1.6 million years ago), there’s evidence that Borneo, the Southeast Asia mainland and Sumatra were connected by land.

Because Borneo’s climate used to be more seasonal, unlike its current tropical characteristics that are present throughout the year, terrestrial animals seeking a more suitable environment were able to move to Borneo.

Thousands of years after this migration process, it is still possible to see similarities between terrestrial species found on Borneo and those from the mainland.

Today, ecosystems continue to be affected by geological and climatic factors, but human influence grows more and more pervasive.

A closer look at:

• Lowland dipterocarp forests

In Borneo’s lowland dipterocarp forests stand giant trees, massive pillars that have existed for over 30 million years. These dominate the lowland tropical rainforests of Borneo, which once covered most of the island.

• Montane forests

Covering 7% of central Borneo, montane forests receive more rainfall than lowland forests. 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.

• Freshwater ecosystems

Constantly fed by rainfall and springs, rivers come crashing down from the mountainous uplands - the Heart of Borneo – all the way down to the island’s coast, carrying life-giving water and a mind-boggling diversity of wildlife.