The Republic of Indonesia occupies a total land area of 1 904 570 km2 within the Southeast Asian archipelago bounded by latitudes 05° N and 11° S and longitudes 94° and 141° E.
The Indonesian archipelago consists of some 13 600 islands, of which about 6 000 are inhabited. Common land boundaries are with Malaysia, with the states of Sabah and Sarawak on Borneo island; with East Timor and with Papua New Guinea. Otherwise, the archipelago lies between the Indian Ocean to the west and south and the Pacific Ocean to the north-east. It is separated from Peninsular Malaysia and Singapore by the Straits of Malacca and the South China Sea, from the Philippine islands by the Sulawesi Sea and from Australia by the Arafura Sea and Timor Sea.
The vast distances within the country are illustrated by the distance from the north-western tip of Aceh province in Sumatra to the south-eastern corner of Irian Jaya, approximately 5 300 km, and from Talaud island, close to the Philippine island of Mindanao; to Roti island, in the south-east of Timor island, roughly north-south at approximately 1 775 km.
General topography of the three largest islands: Sumatra, Kalimantan and Irian Jaya can be characterised by extensive coastal plain and hilly inland areas up to about 1 000 m. These amount to 74 percent of land area in central and southern Sumatra, 40 percent in northern Sumatra, 84 percent in western and central Kalimantan, 50 percent in eastern Kalimantan and 60 percent in Irian Jaya.
The remaining areas are mountainous, formed by the Barisan Range in western Sumatra; the interior ranges, mainly of eastern Kalimantan and the Bird´ s Head, and the Northern and Central Ranges in Irian Jaya. Sulawesi is largely mountainous, with only 40 percent below 1 000 m, mainly in south and south-east. Java is characterised by a series of fifteen volcanoes and other well-spaced mountains. Between them lie fertile plains and a broad northern coastal plain to the Java Sea, with 63 percent of the area below 1 000 m.
The Maluku and Nusatenggara islands are of smaller size, with many volcanoes and mountains. Plains and lower hills are limited to 44 percent (below 1 000 m).
The climate of much of the country is ever-wet or semi-wet, characteristic of Kalimantan, all of Sumatra except the northern coastal strip, Irian Jaya except the south-east, central Sulawesi and most of its northern arm, the Halmahera and Aru islands of the Maluku and south-west Java and the mountainous parts of central Java. All other areas can be classified as semi-arid or monsoon types, such as those found in Nusatenggara, especially the eastern islands. Mountains have a marked effect on local climate.
The bulk of the Indonesian landmasses fall in the ever-wet and semi-wet climates, where the greatest area of forest is found. These typical humid tropics are broadly characterised by mean day temperature of 32° C; mean night temperature of 22° C; diurnal variation in coastal plains 5.5° to 8.5° C and inland 8.5° to 11° C; monthly variation: about 2° C; monsoon winds (but outside the typhoon belt); average annual rainfall 2 500 to 3 000 mm (exceeding 5 000 mm on exposed higher sites); daily average humidity 90 percent, only slightly influenced by monsoon seasons; and thunderstorms occurring all year round, up to 200 days a year, peaking in the afternoon.
The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.