Borneo

One island, three countries

Borneo sits astride the Equator and is the third-largest island in the world, after Greenland and New Guinea. Indonesia holds the largest part, which Indonesians call Kalimantan, divided into five provinces. Along the northwest coast and the northern tip lie Sarawak and Sabah, two states of Malaysia, and between them is the sultanate of Brunei.^[1] It is the only island in the world shared by three countries: about 73% of it is Indonesian, 26% Malaysian and 1% Brunei’s.^[2]

The three never meet at a single point. Brunei is bounded by the South China Sea to the north and by Sarawak on every other side, which also splits it into two pieces.^[4] More than two-thirds of the island’s people live on the Indonesian side.^[1] The name Borneo itself appears to be a corruption of Brunei, the sultanate that dominated the island when Europeans first arrived.^[3]

Dutch south, British north

The Dutch saw Borneo as an outpost of Java and cared most about its south coast. The British saw it as a station on the sea route from India to China, and wanted the north coast with its sheltered harbours. An Anglo-Dutch treaty of 1824 barred the British from settling the islands south of the Strait of Singapore; the Dutch came to read that as all islands south of the strait’s latitude, and used it to oppose British settlement on Borneo.^[3]

The first lasting British foothold was private. Brunei ceded Sarawak to the English adventurer James Brooke in 1841,^[5] and in 1842, as a reward for helping put down a revolt, he became its sovereign ruler. Sarawak then grew at Brunei’s expense: east to the Rajang river by 1853, the Bintulu by 1861, the Baram by 1882, then the Trusan in 1884, Limbang in 1890 and Lawas in 1904–05. In the north, an Austrian, Overbeck, and the Englishman Alfred Dent obtained what is now Sabah from the sultans of Brunei and Sulu in 1877–78, and in 1881 Britain chartered their North Borneo Company despite Dutch protests.^[3] What was left of Brunei became a British protectorate in 1888.^[4]

Drawing the line

To avoid serious incidents, Britain and the Netherlands set up a commission in 1889, and the London Convention of 20 June 1891 fixed a line between their parts of the island, a compromise between the two powers’ biggest claims. It cut the small island of Sebatik in two along the parallel of 4° 10′ N, and after a short stretch along the parallel of 4° 20′ N it followed the main watershed of the rivers west to Tanjung Datu on the South China Sea. As more was learned about the terrain, the line was amended in 1915 and 1928.^[3]

For about 800 miles the border runs along that ridge line, through low mountains under rain forest, and in 1965 the US Geographer noted that in places the exact position of the divide was little known. Only two short stretches were marked on the ground with pillars.^[3]

“The general picture is one of continuous and monotonous forest coverage.”^[3]

From colonies to countries

Japan occupied the whole island in the Second World War. Afterwards Sarawak’s Brooke ruler and the North Borneo Company handed their territories to Britain, which made them colonies in July 1946. Independent Indonesia replaced the Dutch in the south on 28 December 1949, and on 16 September 1963 Sarawak and North Borneo, renamed Sabah, joined Malaya and Singapore to form Malaysia.^[3]

Indonesia protested the new federation; a UN mission reported that a sizeable majority in the two colonies favoured it, but in 1965 Indonesia had not accepted its report, and guerrilla operations from Indonesian territory had taken place along the border. The Philippines also entered reservations over Sabah, based on the old rights of the sultanate of Sulu.^[3] Brunei, still a British protectorate, became independent on 1 January 1984.^[5]

Sharing the forest

On 12 February 2007, in Bali, the three governments signed the Heart of Borneo declaration, promising to manage a network of protected areas and sustainably used forests across 22 million hectares of the island’s interior, almost a third of Borneo. The text says this is done with full respect for each country’s territory and without affecting the ongoing talks on marking the land boundary.^[6]

Borneo may also become home to a national capital. Indonesia is building Nusantara, its planned new capital, in East Kalimantan near Balikpapan; construction began in 2022, and the choice of Borneo is seen as a statement about developing the whole country, not just Java.^[7]