Indonesia

Indonesia is a sovereign republic in Southeast Asia and the largest archipelagic country on Earth. Its roughly 17,000 islands, of which about 6,000 are inhabited, straddle the equator between the Indian and Pacific oceans and extend about 5,000 kilometres from east to west. Its land area is about 1.9 million square kilometres, and its waters, including the exclusive economic zone it claims, bring its generally recognised territory to about 5 million square kilometres. The main islands are Sumatra, Java, Kalimantan (the Indonesian part of Borneo), Sulawesi and the western half of New Guinea. Indonesia shares land borders with Malaysia, Papua New Guinea and Timor-Leste, and it is the most populous country in the Southeast Asia region once the populous islands are counted together. Its position on the tectonic boundary of several plates makes it one of the most seismically and volcanically active places on the planet.

The physical setting of Indonesia is the product of plate collision, a volcanic arc running through Sumatra, Java and the Lesser Sunda Islands, and a sharp divide between Asian and Australasian biota. These conditions produce high mountains, fertile volcanic soils, dense rainforest, and one of the richest concentrations of biodiversity on Earth. They also expose the country to earthquakes, tsunamis, eruptions and floods. The entry therefore moves from the archipelago's structure and geology to its climate, living systems and natural resources, and then to its human geography, including population distribution, land-use pressure and the planned relocation of the national capital.

The entry closes with the environmental and strategic questions that shape Indonesia's future: deforestation and peatland loss, exposure of coastal cities to subsidence and sea-level rise, disaster management, maritime sovereignty under the law of the sea, and the country's reliance on mineral and energy resources alongside its geothermal potential.

Name, borders and territorial extent

Name

Its etymology lies in two Greek stems, one linked to the Indus and the other meaning island, which together convey something close to "Indian islands" From Greek Indos referring to the Indus, combined with nesos meaning island.. Modern usage took shape in the mid-nineteenth century, when the English ethnologist George Windsor Earl proposed the terms Indunesians and Malayunesians for the inhabitants of the "Indian Archipelago or Malay Archipelago", and James Richardson Logan adopted Indonesia as a geographical term for the Indian Archipelago. Sources give different dates for these coinages, from 1847 to 1857.

For roughly three centuries the territory was known as the Netherlands East Indies. The independent state later adopted the name Indonesia, partly because the older colonial label was unacceptable to it The name "Indonesia" was officially adopted after Indonesia became independent in 1945. The Javanese word Nusantara, meaning archipelago, is also the name of the planned capital in East Kalimantan, so the two uses are easily confused; that capital is treated in a later section.

Land borders

Three land frontiers run across islands that Indonesia shares with other states: Malaysia (on the island of Borneo), Papua New Guinea (on the island of New Guinea), and Timor-Leste (on Timor island). The Papuan provinces meet Sandaun and Western provinces of Papua New Guinea. Reported lengths vary by reference. The Malaysian frontier appears as 1,881 kilometers (1,168 miles) in one source and as 2,019 km (1,255 mi) in another, while the total land boundary is given as 2,958 kilometers in one and 3,108.3 km in another.

Maritime boundaries

Sea frontiers connect Indonesia to Australia, India, Palau, Philippines, Singapore, Thailand, and Vietnam. Some reference lists also count China, noting that due to Chinese territorial claims in the South China Sea, there are overlapping maritime boundaries between the two nations around the Riau Islands.

Territorial extent and why figures differ

Published area totals differ because they depend on what is counted. One breakdown gives a total of 1,904,569 km², of which about 1,811,569 km² is land and 93,000 km² consists of inland seas such as straits and bays Of Indonesia's total area 1,811,569 square kilometers (699,451 square miles) is land and 93,000 square kilometers (35,907 square miles) is inland seas. Beyond the coast, the claimed territorial sea 12 nautical miles (22.2 kilometers); exclusive economic zone: 200 nautical miles (370 kilometers). Figures that include these zones describe a maritime domain far larger than the land area, while land-only figures describe something much smaller. Comparing sources therefore requires checking which of these measures is used.

Independence and the Djuanda Declaration

Independence was proclaimed on 17 August 1945, and the Netherlands acknowledged sovereignty on 27 December 1949 The Proclamation of Independence on August 17th, 1945 and the Recognition of Sovereignty on December 27th, 1949 did not automatically unite its whole territory. Under the colonial-era law, the waters claimed by coastal states were narrow, since the coastal countries had a claim for the waters national jurisdiction only 3 miles ashore, which left the seas between islands outside national control.

The Djuanda Declaration of 13 December 1957 changed this. The sea boundaries is no longer based on tidal lines, but on a straight base line measured from the outline connecting the outermost points of the islands, and the determination of territorial waters are increased from 3 nautical miles to 12 nautical miles. Many maritime powers objected, because such baselines also converted high seas within the Country into internal waters. The principle was later written into the UN Convention on the Law of the Sea of 1982, which recognizes the Archipelagic State Principle as claimed by Indonesia. Under its Article 47, the country gained the right to draw straight baselines around its outermost islands and to exercise full sovereignty over the enclosed waters, airspace, seabed, and subsoil. This is the basis of the archipelagic state status that shapes the country's territorial definition today.

Archipelago structure and islands

Indonesia extends about 5,120 km from east to west and 1,760 km from north to south, which makes it the largest archipelagic state in the world. Its islands are usually grouped into four clusters: the Greater Sunda Islands in the west, which include Sumatra, Java, Borneo and Sulawesi; the Lesser Sunda Islands, running east from Bali; the Maluku Islands; and Papua at the eastern end. The Greater Sunda group is the core of the archipelago, and the rest of the country is organised around it. The islands are often treated as one archipelago whose parts are linked by sea rather than land.

No agreed total exists. The official figure of 17,508 comes from Law No. 9 of 1996 on Indonesian maritime territory. A 2007–2010 geospatial survey by the national mapping agency Bakosurtanal counted 13,466 islands, while an earlier 2002 survey by the aerospace agency LAPAN reached 18,307. Most general references therefore give a range of roughly 17,000 to 18,000. About 6,000 islands are described as inhabited, which is roughly a third of the total. The inhabited figure is itself loose, because sources do not apply a single threshold for what counts as settled.

The modern extent of the state rests on a legal change made in 1957. On 13 December 1957, the government under Prime Minister Djuanda Kartawidjaja declared that the waters surrounding, between and connecting the islands form part of Indonesia's territory. The declaration replaced tidal-line boundaries with straight baselines drawn between the outermost points of the islands, and it extended the territorial sea from 3 to 12 nautical miles. It also removed the high seas that had lain between the islands. Indonesia's concern was that foreign warships could otherwise pass freely through its waters, a security issue that the government saw as urgent. The legal reasoning was later refined by the jurist Mochtar Kusumaatmadja, who turned the political declaration into an archipelagic-state concept drawing on a 1951 International Court of Justice ruling.

Other states were not quickly persuaded. Indonesia's attempts to gain recognition at the first and second UN Law of the Sea conferences were not particularly successful, and the issue was taken up as a separate item only at the third conference in 1973. The concept was adopted in Part IV of the 1982 UN Convention on the Law of the Sea, which was adopted at Montego Bay on 10 December 1982 and entered into force in 1994. Indonesia ratified the convention through Law No. 17 of 1985. Under this framework, the sea between islands became part of the national territory and subject to Indonesian sovereignty, while the convention also provided for archipelagic sea lanes that allow foreign ships to transit. In practical terms, the claim changed the country's maritime footprint: one 2011 regional paper estimates that Indonesian territorial sovereignty grew from about 2 million km² in 1945 to about 5 million km² by 1957, and current figures put land at about 1.9 million km² against territorial waters of roughly 3.3 million km².

The islands themselves differ greatly in size and character. Sumatra, Borneo and New Guinea are among the largest islands in the world, and Java, though much smaller than these, carries the majority of the population. Terrain also varies widely: much of Kalimantan, southern New Guinea, eastern Sumatra and northern Java consists of lowland plains, while Sulawesi, western Sumatra, southern Java, the Lesser Sunda Islands and the Maluku Islands are dominated by rugged, volcanic topography. Between these larger islands lie countless small islets, reefs and coral cays, many uninhabited and scattered across seas such as the Banda Sea and the Java Sea. This uneven mix of large mountainous islands and tiny, remote specks is one reason why transport, administration and settlement remain difficult across the archipelago.

Tectonic setting and plate boundaries

The archipelago sits where the Eurasian, Indo-Australian, Pacific and Philippine Sea plates meet, and the first three are major and are constantly moving and colliding. The Alpide–Himalayan belt and the circum-Pacific Ring of Fire both pass through the country, which is why it ranks among the most tectonically active regions on Earth. Its two continental foundations differ in age and character. In the west, the Sunda Shelf is a tectonically stable extension of Southeast Asia's continental shelf, which is also roughly coterminous with the Sunda plate. In the east, the Australian plate carries the Sahul Shelf, a plate margin that continues the Australian continent northward.

The most consequential boundary is the convergence of the Indo-Australian plate with the Sunda plate. Relative to the Sunda plate, the Indo-Australian plate moves NNE at about 52–77 mm per year. West of about 120°E, the Indo-Australian plate subducts beneath the Sunda plate at the Sunda–Java trench, with convergence nearly orthogonal south of Java and oblique farther west. East of 120°E, subduction gives way to collision between the Indo-Australian and Sunda plates at the Timor and Seram troughs. The subduction interface, known as the Sunda megathrust, runs along roughly 5,500 kilometres off the coasts of Myanmar, Sumatra, Java and Bali, terminating off the northwestern coast of Australia. It is one of the most seismogenic structures on Earth.

Subduction also builds the volcanic arc. The chain of active volcanoes that formed Sumatra, Java, Bali and the Nusa Tenggara islands emerged mostly within the last 2–3 million years. In the north and east, a second, more complicated system operates. Pacific plate subduction beneath the Eurasian plate produced volcanoes in North Sulawesi, Sangihe and Halmahera. The three major plates meet at a triple junction south of New Guinea's Bird's Head. Here the boundaries are not simple lines. Each boundary between a pair of plates is a relatively narrow zone of deformation, typically on the order of 100–200 km wide, and it contains subduction zones and major strike-slip faults. Sulawesi is a clear example, where the tectonic setting involves both subduction and strike-slip motion along the boundaries of several microplates.

Oblique convergence also distributes strain sideways. Because convergence along the boundary is highly oblique, the overriding Sunda plate is deformed and that strain is accommodated by strike-slip motion along the Great Sumatran fault. Dip-slip ruptures can also occur deeper within the subducting slab. The 2009 magnitude 7.6 earthquake near Padang was caused by reverse faulting at a depth of 80 km.

Plate geometry also shaped the land area through sea-level change. Throughout the Pleistocene and late Pliocene, glaciation cycles caused sea-level fluctuations that repeatedly led to land connections between islands that today are separated by ocean channels. At the Last Glacial Maximum, sea level was low enough that the Sunda shelf was fully exposed, joining mainland Southeast Asia to Sumatra, Java, Borneo and possibly Palawan. The Sunda Shelf exposure contributed to a high degree of endemism and local distribution discontinuities across the region. On the eastern side, the Arafura Shelf formed a land bridge between Australia, New Guinea and the Aru Islands, and these lands share many marsupial mammals, land birds and freshwater fish as a result.

Volcanism

Indonesia has more than 120 active volcanoes, and government seismologists monitor them as part of a national network. The volcanoes form a chain along the plate boundary where the Indo-Australian plate descends beneath the Eurasian plate, running from Sumatra through Java and Bali to the Lesser Sunda Islands. Magma generated above the subducting slab rises to the surface at these arcs, so the volcanic belt follows the same line as the trench and the island chain.

Java has the densest concentration of population and some of the most hazardous volcanoes. Mount Merapi, on the border of Central Java near Yogyakarta, is the country's most active volcano. Its eruption in late October and November 2010 produced pyroclastic flows that ran down the Gendol valley for about 15 km, and it killed several hundred people. Published death tolls differ: estimates range from about 324 to 386, depending on the source and the date of the count. The eruption also forced the evacuation of more than 300,000 residents, and it remains the reference case for volcanic risk management in the country. Kelud, in East Java, is another of the island's dangerous volcanoes, and its crater lake has repeatedly produced sudden lahars when the lake water is displaced by eruptions.

Two historical events show how volcanoes can generate tsunamis. The eruption of Krakatau in the Sunda Strait in 1883 was an explosive, caldera-forming event; its final phase sent pyroclastic material into the sea, and the resulting waves killed roughly 36,000 people on the coasts of Java and Sumatra. On 22 December 2018, the flank of Anak Krakatau, which had been erupting since June of that year, collapsed into the caldera to the southwest of the volcano. The displaced water produced waves that reached up to about 13 m on the coasts of Sumatra and Java, and at least 437 people died. Because no tsunami warning system was linked to volcanic flank failure, the waves arrived with almost no time for evacuation.

The hazards of Indonesian volcanism fall into several categories. Ash falls disrupt agriculture, aviation and respiratory health; tsunamis and pyroclastic flows are the most lethal in the short term; and lahars, which are mudflows of volcanic debris, can travel far down river valleys during the rainy season. Emergency planning therefore depends on monitoring alert levels, hazard maps and evacuation routes for communities living on the lower slopes of major peaks.

Volcanic activity also has benefits. Weathered volcanic ash supplies nutrients to soils in Java and other islands that support intensive cultivation. The same heat sources are exploited for geothermal energy, and volcanic landscapes such as lakes, craters and cones attract tourism. These benefits explain why large populations continue to live close to active volcanoes despite the risks.

Earthquakes and tsunamis

The 2004 Indian Ocean earthquake and tsunami is the most consequential seismic disaster in Indonesia's modern history. An undersea earthquake with a magnitude of 9.1 struck off the coast of the Indonesian island of Sumatra on the morning of December 26, 2004. The first giant waves reached Banda Aceh, an Indonesian city of about 300,000 people, within 15 or 20 minutes of the earthquake. Few residents realized that the earthquake they had felt could cause a tsunami, and there was little time to flee to higher ground. Indonesia's Ministry of Health confirmed 131,028 deaths by June 2005, mainly in Aceh province on northern Sumatra, with another 37,000 people missing. Sri Lankan authorities reported 31,229 confirmed deaths. Household surveys in nine tsunami-affected Aceh districts later found that 17.0% of the pre-tsunami population had died or gone missing, and crude mortality reached 23.6% in Aceh Jaya on the west coast.

Fourteen years later, a different mechanism produced a similar lesson. On 22 December 2018, a tsunami in the Sunda Strait left 437 dead and thousands injured along the western Java and southern Sumatra coastlines. Researchers traced it to a landslide of under 0.2 cubic kilometres on the southwestern flank of Anak Krakatau, which was erupting at the time. The landslide did not produce strong short-period seismic waves, so the precursory ground shaking gave no tsunami warning. The eruption had begun about 24 minutes before the tsunami, and the waves struck at night, which made visual recognition harder for coastal communities (16-8). The absence of any alert in the first minutes contributed to the high casualty count on both affected coasts.

The failure of warning systems became more visible in 2018, when a quake and tsunami struck Palu in Central Sulawesi and claimed 844 lives, at the latest count. Text message alerts were sent, but the earthquake had brought down power and communication lines around the area, so the alerts were never received. None of the 21 buoys that made up the tsunami warning system worked. Indonesia's land-based network relies on tidal gauges, and the tidal gauges were so far away from Palu that they registered only a small rise in water level as the waves formed.

Before 2004, tsunami risk was considered low, with limited seismic observation and real-time sea-level monitoring, and there was no tsunami warning system. Afterwards, Indonesia introduced a network of buoys, sea-level gauges and seismometers that can send alerts to countries' tsunami warning centres within 10 minutes of a quake. The buoys proved fragile. According to the spokesman for the weather, climate and geophysics agency (BMKG), all 22 buoys had been broken since 2012. Some were damaged by fishermen anchoring near them, others were vandalized, and a few were stolen. Maintenance was estimated at about $2.3 million a year, but the government never allocated enough money in the state budget to fund this necessary maintenance. Analysts differ on the root cause: some observers noted the lack of functioning buoys, while others argued that the lack of reliable funding played a key role, and design shortfalls and difficulties with last-kilometre ground alerts also contributed.

Current efforts build on the buoy-based approach while adding other tools. The Ina-TEWS system requires maintenance and supervision, especially since 22 buoys were declared lost or damaged in 2012–2018. By 2024, 533 seismograph sensors were planned to be in place, which officials said would make warnings more reliable, timely and accurate. Officials have also argued that the Sunda Strait tsunami was caused by volcanic activity leading to a submarine landslide rather than by tectonic activity, so data on volcanic activity must be included in the warning system. Because technology alone does not reach residents, community understanding, awareness and preparedness are needed for these innovations to be effective.

Mountains, highlands and relief

Puncak Jaya, also called Carstensz Pyramid, rises to 4,884 m (16,024 ft) on the island of New Guinea and is the highest peak in Indonesia and in Oceania. It lies in the western part of the Maoke Mountains, in the highlands of Central Papua. Other significant peaks in the same range include Sumantri (4,870 m), Ngga Pulu (4,863 m) and Carstensz East. The rocks of the range have a marine sedimentary origin, and its peaks are among the tallest in the tropical Pacific.

Puncak Jaya is unusual because it sits close to the equator yet carries ice. Its elevation allows glaciers to persist on the upper slopes, but since the 1850s large portions of these glaciers have melted. The Carstensz Glacier is now classed as retreating, and the range's ice is one of the clearest visible signs of climate change in the country's highlands.

East of the Sudirman Range, the Jayawijaya Mountains form the eastern section of the Maoke system. The range extends for 370 kilometres east of the Sudirman Range to the Star Mountains. Its highest point is Puncak Mandala, at 4,760 m, and the Baliem River has its source in the range. The range's small glaciers have also shrunk sharply: their depth declined from 32 m in 2010 to 8 m in 2021. Because air temperature falls with altitude, the Papuan highlands are much cooler than lowlands at the same latitude, and the valleys between these ranges have historically been settled by highland communities largely separated from the coast.

In western Indonesia the main relief feature is the Bukit Barisan, which runs along Sumatra. The Barisan range covers nearly 1,700 km from the north to the south of the island. Its name, which in Malay means something like "row of hills", reflects how the range stretches end to end along the island of Sumatra. It consists primarily of volcanoes shrouded in dense jungle cover, with pine forests on the higher slopes. The highest summit is Mount Kerinci, a stratovolcano of about 3,805 m that forms part of a chain spanning from the extreme northwest of the island in Aceh province to the extreme southeast in Lampung province. In southern Sumatra, the western spurs of the range thrust eastward, forming deep ravines and valleys.

Java's relief follows the same volcanic arc. The island's mountains are largely volcanic cones, and the Sunda Arc stretches from Sumatra through Java, ending at Flores. Semeru is Java's highest peak and has been active for decades, with ash often released from near its summit. Semeru is Java's highest peak and has been active for decades. The volcanic chain has produced a fertile, densely settled landscape of high ground, which is discussed further in the section on volcanism and agriculture.

On many of the large islands, the basic pattern is a coastal plain surrounding a mountainous interior. Steep slopes, dense forest and deep valleys restrict where roads, towns and farms can be built, which is one reason why transport links between coastal settlements and inland areas remain limited in parts of Sumatra, Sulawesi, Kalimantan and Papua.

Rivers, coasts and seas

Most of Indonesia's major rivers drain the large islands of Borneo, Sumatra and Papua. The Kapuas is the longest, at about 1,143 km, which makes it the country's longest river. Longest river: Kapuas River 1,143 km. It rises in the Müller Mountains of central Borneo, and sources differ on the lengths of the other rivers. The Barito has a total length of 1,090 km (680 mi) and a drainage basin of over 80,000 km2 in South Kalimantan, though a Indonesian-language list gives its length as 900 km. It flows southward into the Java Sea and passes the city of Banjarmasin. The Mahakam, in East Kalimantan, flows 980 kilometers (610 miles) from the district of Long Apari in the highlands of Borneo, to its mouth at the Makassar Strait.

Outside Borneo, the Musi crosses South Sumatra for about 750 kilometers, and Palembang, the capital of South Sumatra, is located on the banks of this river. In Papua, the Digul has a depth of about 20 meters and flows more than 500 km. In the interior it is the only access to transportation in several areas that have not been reached by land roads. Along the lower reaches of many of these rivers, the land is flat and waterlogged, which is why swamp forest and floodplain characterise much of the coastal lowland.

Lakes are, by comparison, a minor feature of the landscape. There are also some scattered inland lakes as well which are relatively small in size. The principal exception is Lake Toba in North Sumatra. The lake fills the caldera of a supervolcano and is about 100 kilometres (62 miles) long, 30 kilometres (19 mi) wide, and up to 505 metres (1,657 ft) deep. The central part of the lake is occupied by the large Samosir Island. Its outflow is the Asahan River, which eventually makes its way and empties into the Strait of Malacca. The caldera was formed by an eruption about 75,000 years ago, which makes it one of the most significant volcanic features in the country (see volcanism).

Estimates of the coastline also vary. One reference gives 54,720 km (34,000 mi), while a 2005 marine study put it at about 108,920 km, and a fisheries profile gives 108,000 km. The difference reflects how the coast is measured, not a change in the land. The surrounding seas are shallow in the west and deeper in the east. The Java Sea is an extensive shelf sea of about 1,600 km (990 mi) east-west by 380 km (240 mi) north-south, with an average depth: 46 m. It formed as sea levels rose at the end of the last ice age. The Arafura Sea lies over part of the Sahul Shelf, and during low sea levels of the last glacial maximum the shelf formed a land bridge between Australia and New Guinea. The depth of the sea is 50–80 m (160–260 ft) in most places. The Banda Sea is much deeper; its maximum depth is 7,351 m (24,117 ft), and it is one of the seas around the Maluku Islands. Taken together, these seas are located between the Indian Ocean and the Pacific Ocean, which gives Indonesian waters their role as a link between the two.

Along many shores, estuaries, river deltas and mangrove wetlands form a transitional zone between land and sea. These areas trap sediment, shelter juvenile fish and absorb storm surges, so they support fisheries and protect coastal settlements. Because they are often converted to ponds or built over, their loss tends to increase flood exposure in low-lying areas.

Climate and seasonal patterns

Indonesia straddles the equator, so its climate is equatorial and tropical, with high temperatures and humidity throughout the year. Temperatures vary little across the seasons. Average readings are about 28 °C on the coastal plains, about 26 °C inland, and about 23 °C in the highest mountain areas, and humidity often stays between 70 and 90 percent. Seasonal change therefore appears mainly as a shift in rainfall rather than in temperature, and the country has no summer or winter in the European sense.

The annual rhythm is set by the monsoon system, which reverses direction between the two halves of the year. Winds from the southeast blow roughly from June to September and carry dry air from the Australian interior, producing the dry season. From about December to March, northwesterly winds bring moist air from mainland Asia and the Pacific, and humid Indian Ocean breezes reinforce them, producing the wet season. Many sources place the dry season in roughly April or May to October and the wet season in November to March or April, but the timing shifts from place to place. The wet season on Bali, Java and the Lesser Sunda Islands generally falls between November and March, while in Sumatra it can last longer. Southern coasts and islands south of the equator tend to receive more rain during the southern monsoon, and northern coasts and islands during the northern monsoon. Some islands in southern Maluku have rainfall patterns that depend heavily on local wind currents and are hard to predict.

Rain within the wet season usually arrives in heavy bursts, often in the afternoon, and is frequently accompanied by thunder. Some parts of the archipelago experience more thunderstorms than almost anywhere else in the world, yet the same areas also receive many hours of sunshine. Rainfall totals and seasonal intensity depend on elevation, exposure to prevailing winds and distance from the sea. Mountain slopes facing the wind receive more rain than sheltered valleys, and coastal locations respond quickly to shifts in the monsoon. Many locations also experience two wetter periods a year, as the Intertropical Convergence Zone (the Doldrum Belt) passes over the islands.

Climate variability driven by ocean-atmosphere cycles has a larger effect on Indonesia's dry seasons than the regular monsoon. El Niño is a warming of sea surface temperatures in the equatorial Pacific Ocean. During El Niño years, the rainfall that normally falls over Indonesia and the western Pacific shifts eastward toward the central Pacific, and much of Indonesia becomes drier than usual. The effect is strongest when El Niño combines with a positive phase of the Indian Ocean Dipole, which further suppresses rainfall across equatorial Southeast Asia. The 1997 and 2015 events produced some of the most severe fire seasons of recent decades. In 2015, fires burned around 2.6 million hectares, and studies have linked the smoke from that season to premature deaths across Indonesia, Malaysia and Singapore. Public health impacts of this kind are a major reason why the phenomenon receives close monitoring.

The fire hazard is especially serious in peatlands in Kalimantan, Sumatra and Papua. Peat normally stays too wet to burn, but in prolonged drought the soil can dry enough for fire to spread underground and smoulder for long periods, releasing dense smoke that is hard to extinguish. Indonesian fire activity follows a consistent seasonal pattern that intensifies from mid-year and peaks in September and October, although fire seasons can also be unusually active in years without drought when temperatures are high. In the 2026 dry season, the national meteorological agency reported that about 90 percent of the country received little or no rainfall in early August, and it projected that El Niño conditions would persist into early 2027. Each season is therefore shaped by the interaction of the monsoon cycle, the broader ocean-atmosphere state and local land management.

Biogeography and biodiversity

The Wallace Line and Wallacea

The Wallace Line is a faunal boundary drawn in 1859 by the British naturalist Alfred Russel Wallace, and it separates the biogeographic realms of Asia and Wallacea, a transitional zone between Asia and Australia. The line runs between Borneo and Sulawesi, and between Bali and Lombok. West of it, the fauna is largely Asian. Wallace's Line separates an Asian fauna which includes primates, carnivores, elephants, and ungulates from the marsupial fauna of Australia and New Guinea. Birds show the boundary most clearly, since many species do not fly over even narrow stretches of water.

Wallacea lies between the two faunal realms. Its islands have not been directly connected to either region, due to the deep water straits at its borders, and so could only be colonised by over-water dispersal. The western side of Sundaland was different. Its islands were intermittently connected by land during the Pleistocene ice ages, up to as recently as 21,000 years ago when the sea level was as much as 120 m below current levels. This land connection allowed the mainland fauna of the Sunda shelf to spread, while the deep straits limited its reach eastward.

Endemism and species richness

Indonesia's species totals are high by any count, though figures vary by compilation. Conservation International considers Indonesia to be one of the 17 "megadiverse" countries. About 12% of the world's mammals (515 species) occur in Indonesia, ranking it second, after Brazil, at the global level. Estimates of mammal and bird totals differ between sources, and the Indonesian Ministry of the Environment estimates that more than half of Indonesia's species are still unrecorded.

Endemism is especially high on the islands. A national checklist of vascular plants records 30,466 species belonging to 2968 genera and 317 families, and Indonesian New Guinea had a much higher proportion of locally endemic species than other regions (59%). On Sulawesi, 98% of its non-flying mammal species, 37% of its bird species, and 26% of its reptile species being endemic. Birds show a similar concentration: a total of 542 endemic bird species are recorded, and more than half are concentrated in the Wallacea region.

Isolated island populations

Island isolation has produced well-known species with very restricted ranges. The Komodo dragon, the world's largest lizard, is restricted to the islands of Komodo, Padar, Rinca, and Flores in the Wallacea hotspot. The orangutan, by contrast, survives only in the forests of Sumatra and Borneo, where it is endangered. Several other species, including the anoa, are found nowhere else; Species including the anoa, Komodo dragon and Wilson's bird of paradise can be found only in Indonesia. Sulawesi also hosts tarsiers – tiny, goggle-eyed creatures, which illustrate how distinctive the island fauna can be.

The Coral Triangle

Indonesia lies at the heart of the Coral Triangle, which is a major centre of marine diversity. 600+ species of reef-building coral, roughly 75% of all known species occur in the region, along with 3,000+ species of reef fish recorded across the region. At its heart lies Indonesia, which boasts the largest area of coral reefs within the region. Reef systems support fisheries on which coastal communities depend, but they are under pressure. 85% of coral reefs in the Coral Triangle are threatened or extremely threatened, and the main threats include habitat degradation, pollution and unsustainable fishing.

Soils, agriculture and land use

Indonesia's farming geography follows its geology. Much of Java's bedrock is andesitic volcanic material, and the island's most productive soils formed from it rocks on Java are primarily andesitic volcanics. Similarly fertile soils occur on Sulawesi, where they are also derived from or enriched by basic andesitic volcanic material. On the slopes of active volcanoes, new material keeps arriving, so volcanic soil often experiences material renewal every time. For centuries the Prambanan Plain, which lies beneath Merapi, was prized for its rich and fertile volcanic soil perfect for intensive rice cultivation. Upland soils on the Bromo slopes in East Java also matter beyond the farm gate, because the watershed they form feeds aquifers that support lowland rice areas and drinking water supply to nearby cities.

Soil quality is not uniform, however. Indonesian volcanic soils are mostly acidic, with pH values between 3.4 to 6.7, with an average of 5.4, which limits the availability of macronutrients. Sumatra's most productive soils are the andisols of its northeastern coast, which developed on the andesitic volcanic sediments there, while Sumatra's bedrock is largely rhyolitic. The poorest agricultural land is often peat. The Mega Rice Project of the mid-1990s aimed to open roughly one million hectares of peatland for rice. Drainage works ran over thousands of kilometers of canals dug without environmental assessment, and migrants from Java and Bali were settled on the cleared land. The peat proved too unforgiving for the kind of rice cultivation practiced on the mineral-rich volcanic soils of those islands. A later pilot in a former project area produced less than 3 tons of rice per hectare, about half the yield in Java and Bali. The government eventually abandoned the scheme, and the drained land still burns on a large scale almost every year.

Agriculture is organised around a few major crops. Rice remains the staple, being the most consumed food source of carbohydrates in Indonesia. Volcanic soils on the upper slopes are used for plantations, food crops, horticulture and rice fields , and steeper slopes between about 15 and 45 percent are considered suitable for plantation crops such as tea, coffee, quinine, and cinnamon. Oil palm has become the most dynamic crop. Its planted area grew by 600 percent between 1990 and 2010 to 7.8 Mha, and by 2015 Indonesia had 11.1 Mha of industrial-scale oil palm plantations, with 5.9 Mha in Sumatra, 5.0 Mha in Kalimantan, and 0.2 Mha in Papua. Official statistics for the end of 2024 put the total area of oil palm estates in Indonesia reached 16.01 million hectares. Production is overwhelmingly dominated by just two major islands: Sumatra and Kalimantan, although the growth has shifted, with Kalimantan now the main driver of expansion while Sumatra shows stagnant or declining trends.

Ownership structure is mixed. Large private estates hold the largest share, but smallholders are a major group. In 2024 smallholders controlled 42.9 percent of the national oil palm area. This differs from other tree crops, where smallholders own the majority of plantations and supply most of the national output. The rise of independent smallholders accelerated after decentralisation, which contributed to rapid oil palm expansion, especially among independent smallholders. Productivity, however, is uneven. Smallholder yields are estimated to be 50% lower than the potential attainable yield, whereas the yield of government and private estates is estimated to be between 85% and 90% of that potential.

Competing land claims are a persistent problem. Forest areas and smallholder fields without formal title are often classified by the government as "non productive lands" or "bare lands" and are targeted for conversion to oil palm plantations. The tenure gap is significant: around a quarter of all smallholder oil palm area in Indonesia falls within the State Forest, where farmers typically cannot obtain nationally recognised title. The State Forest designation of 1967 covered about 70% of Indonesian land area including already-farmed customary community lands. Land disputes are concentrated in certain provinces; according to the NGO Sawit Watch, West Kalimantan has the second highest level of land conflict related to oil palm plantations in Indonesia, after South Sumatra. The contrast between Java and the outer islands is stark. Java is intensively farmed on a small land base, whereas the outer islands hold most of the new plantation expansion, and Java and the eastern islands have minimal coverage (typically <0.15 million hectares) of oil palm.

Deforestation, peatlands and fire

Forest loss in Indonesia is closely tied to commercial land use. Clearance has been driven mainly by oil palm estates, pulpwood plantations, mining and logging, with the heaviest losses in Sumatra, Kalimantan and Papua. Expansion of palm oil and pulp and paper is described as the greatest contributor to the country's greenhouse gas emissions. Because concessions often extend into forest and mangrove margins, they also reach carbon-rich soils. Where that happens, the exposed peat becomes a fire hazard as well as a source of emissions.

Peatlands are waterlogged deposits of partly decayed plant material, and in parts of Kalimantan they can be more than 20 metres deep. Waterlogging slows decomposition, so carbon can accumulate underground for thousands of years. Drainage reverses this. Conversion of degraded peatland into plantations or industrial areas leaves the soil dry and easy to ignite. Peat fires are also hard to extinguish, since they can burn underground for months. Once alight, peat releases CO₂, methane and carbon monoxide, which adds to the national total of greenhouse gas emissions tracked within the carbon-cycle.

The scale of these events can be seen in earlier episodes. In 2013, a year that was not a drought year, fires in Central Sumatra burned an estimated 163,336 hectares, of which 137,044 ha (84%) were on peat. Most burning was confined to deforested lands, and the resulting emissions were considerable, representing 5–10% of Indonesia's mean annual GHG emissions for 2000–2005. The 2015 fires were larger still. Their emission rate exceeded the fossil fuel CO2 release rate of the European Union, and the 2015 total was the largest seen in maritime southeast Asia since those associated with the record breaking El Niño of 1997. The 2013 case also showed that extreme air pollution episodes in Southeast Asia are no longer restricted to drought years.

The 2026 season is another example of this pattern. Fires in the archipelago released more than 23 million metric tons of carbon between August 28 and September 3, a figure higher than the 20.7 million metric tons from the same period in 2015, a strong El Niño year. Analysts linked the drier conditions to the El Niño event, which made fires easier to spread. The smoke has crossed borders. Haze drifted across Malaysia and Brunei, triggering air quality advisories. In the Philippines, the haze led officials to shutter schools in cities and provinces, and in Singapore it pushed air quality to an "unhealthy" level. Within Indonesia, PM2.5 pollution in Pontianak repeatedly exceeded 250.5 micrograms/m³, a level classed as hazardous. Haze exposure is therefore a public health concern, as well as an air quality one.

Forest and peatland protection has relied heavily on policy instruments. In May 2011, a Presidential Instruction imposed a two-year moratorium on issuing new permits for use of primary natural forest and peatland. The measure was later made permanent. Environment and Forestry Minister Siti Nurbaya Bakar said President Joko Widodo had signed the permanent extension on Aug. 5, 2019. The ban covers primary forest and peatland, but not all forest. It does not apply to secondary forests, which Indonesian law defines as areas that have previously been logged to any extent. Campaigners estimate that 42.2 million ha of secondary forest remain potentially at risk of deforestation. Boundary revisions have also weakened the coverage. Greenpeace reports that the protected area was cut by 2.7 million hectares after ten revisions, and that fires and deforestation have also ravaged those areas which retained protected status.

Restoration has proved difficult. Pantau Gambut, a watchdog organisation, found that 52 percent of peatland that received government intervention between 2015 and 2024 remained degraded and prone to fires. Enforcement is another weak point, since 638,136 ha of oil palm concessions overlapped with the forest and peatland moratorium area in 2020.

Policy debates remain centred on a basic trade-off. Revenue from plantation crops, pulp and mining supports employment and exports, while the same activities add to carbon emissions, biodiversity loss, health costs from haze and disputes over community land rights. Each of these pressures is pursued through different government agencies and different legal instruments, which complicates efforts to reconcile them.

Population distribution and urbanization

Estimates place Indonesia's population at about 281.2 million in 2023, according to Our World in Data, which projects it to reach 295.5 million by 2100. The country ranks fourth in the world, after China, India and the United States. Growth has slowed from earlier decades, and the growth rate in 2023 was 0.8%, a figure that combines natural increase with migration.

The population is heavily concentrated on Java. Despite covering only seven percent of the total land area, around 56 percent of Indonesians live on Java, and the island holds the country's largest cities and most of its economic activity. In terms of urban residence, a 2012 analysis of census data found that about 80.5 million of the urban population, or 68 percent, lived in Java, while 37.8 million lived on other islands. This density is one of the main reasons for the government's long-running efforts to redistribute people.

Those efforts took the form of the transmigration programme, which has roots in the colonial era. The first transmigration project, then known as kolonisatie or colonization, took place in 1905, and after independence the scheme was revived under the Sukarno government to address food shortages and weak economic conditions. Its largest phase ran under Suharto's New Order. Between 1979 and 1988, the programme assigned two million voluntary migrants from the inner islands of Java and Bali to nearly 900 new settlements across the Outer Islands. Its stated goals combined poverty relief, population balance and national integration. It may also have been intended to encourage a single national identity to augment or replace regional identities. Estimates of total numbers vary considerably with the period counted. One source puts the figure at nearly five million people between 1972 and 1990, while another reports that between 1969 and 1992 the programme relocated about 1.5 million families.

The programme's consequences remain contested. Researchers have noted that the scheme created a lasting shift in ethnic composition, as the programme created an initial shock to ethnic diversity, which persisted for decades. Critics have argued that the resettlement brought high environmental, social, and financial costs, while doing little towards relieving population pressure on Java. In Kalimantan, the arrival of migrants has been linked to disputes over land, with a Forest Peoples Programme report describing conflict between transmigrants and indigenous people in the outer islands, particularly in Kalimantan.

Urbanization has grown alongside these rural migrations. In 1950, Jakarta was the only city with more than one million inhabitants. By 1980, Surabaya, Bandung and Medan had joined that group, and by 2010 the number had risen to 10. Today the largest urban region is Greater Jakarta, known as Jabodetabek, which reached 32.3 million people in official estimates for mid-2024. The region is the centre of government, culture, education, and economy of Indonesia. Growth has spread outward: population growth in central cities like Jakarta has slowed, while surrounding areas such as Bogor, Tangerang, Bekasi and Depok have expanded rapidly. Other large metropolitan areas include Bandung, the third-largest metropolitan area in the country with more than 8.5 million inhabitants, and Surabaya, whose metropolitan area is larger in population than Bandung's but includes more rural areas. Medan is the largest urban area outside Java.

Rapid urban growth has brought heavy strain. In the Jakarta–Bandung corridor, increased road access has converted agricultural land into built-up areas, and in Bandung, constant population growth has caused severe problems for the mobility system, due to a lack of adequate public transport and traffic management. These pressures, including congestion, pollution and infrastructure shortfalls in Jakarta, were among the reasons for the later decision to relocate government functions.

Capital relocation to Nusantara

The plan to move the national capital from Jakarta to Nusantara, a site in East Kalimantan on the Indonesian part of Borneo, rests on a sequence of legal acts. The first was the 2022 State Capital Law (Law No. 3/2022), which gave Nusantara formal standing as the future seat of government. The law's Article 39(1) keeps the position, function and role of the national capital in Jakarta until the president issues a decree relocating the capital. Officials justified the move by pointing to Jakarta's crowding, smog and sinking ground. The transition was designed to be gradual, with the handover tied to the completion of infrastructure.

The executive later set a concrete timetable. Presidential Regulation No. 79 of 2025 updated the government's 2025 work plan and set 2028 as the new target year for relocation. Under this scheme, Jakarta would keep its legal standing and its economic weight, while Nusantara would house the executive, legislative and judicial branches. The regulation's benchmarks include moving between 1,700 and 4,100 civil servants to the new city, although a later parliamentary statement referred to 4,100 civil servants to be relocated by 2028. Sources differ on the signing date, with one giving 30 June 2025 and another stating that the regulation took effect on July 30, 2025. A 2028 target does not replace the formal decree. The target does not by itself substitute for the separate presidential decree needed to transfer the capital.

In May 2026 the Constitutional Court rejected a judicial review of the 2022 law, in case 71/PUU-XXIV/2026. The petitioner had argued that a 2024 law on Jakarta's special-region status had removed the capital function from Jakarta before any decree existed, which left a legal gap. The judges disagreed. Justice Adies Kadir said Nusantara had already been designated in legal and political terms, but that the transfer itself was still waiting on a presidential decree. The court therefore concluded that no constitutional vacuum existed, with Jakarta continuing to serve as the seat of decision-making until a transfer decree is issued. The court also tied the question to Article 73 of the 2024 Jakarta law, which takes effect only when the president formally decides the transfer. Jakarta's provincial government has kept its existing designation for the same reason, since the transfer has not legally occurred.

Preparations are moving unevenly on the ground. The Nusantara Capital Authority (OIKN) reported that around 500 of its staff had moved to the new capital since March 1 of this year. The vice president's office building in Nusantara is complete, and his Jakarta workspace is expected to be cleared during 2026. Construction is organised into five phases, with the last projected for completion by 2045. This long horizon contrasts with the 2028 political-capital target, which means the city would function as a seat of government well before its build-out is finished.

Funding has been the main source of controversy. Reported state funding fell after Prabowo Subianto took office in October 2024, and the budget was affected by spending cuts in early 2025. A February 2025 presidential instruction reduced the Ministry of Public Works budget, and the funds for constructing the capital were blocked, raising concerns that work would stall. The authority later reported that the budget had been unblocked, and the 2026 state budget includes Rp6 trillion (around US$370 million) for continued development of the new capital. Critics have also questioned whether the city could be populated at all. Some observers think Nusantara could become a ghost town, given that its population is made up largely of civil servants and construction workers. Environmental concerns have been raised as well, and Greenpeace has cited deforestation and ecological damage linked to the project.

Coastal flooding, subsidence and climate vulnerability

In Jakarta, land subsidence and sea-level rise compound each other. Parts of the northern coast have lost more than four metres of elevation since the 1970s, a pace seldom matched elsewhere in the world (In some northern coastal areas, the ground has subsided by more than 4 meters since the 1970s – at a rate rarely seen in the world.). Survey data from 1982 to 2010, combining levelling, GPS and satellite radar, show typical sinking of about 1 to 15 cm a year, rising to 20 to 28 cm a year in parts of the north (Levelling, GPS, and satellite radar record subsidence of roughly one to fifteen centimetres a year across the city between 1982 and 2010, and twenty to twenty-eight centimetres a year in parts of the north). The mechanism is hydrological. Withdrawals that outpace groundwater recharge lower the water pressure that supports the aquifer material, and the sediments above then compact (groundwater extraction that exceeds aquifer recharge could lead to a decline in groundwater levels (piezometric head), reducing the hydrostatic pressures supporting the aquifer material and causing land subsidence.). Radar studies identify pumping as the principal driver, while building loads and the natural consolidation of sediments also contribute (radar interferometry identifying groundwater extraction as the principal cause; besides also by building/construction load and natural consolidation of sedimentary layers.). The process is sometimes described as land subsidence.

Subsidence raises flood exposure because much of the city is already low. About 40 percent of Jakarta is below sea level. Tidal water already reaches some coastal neighbourhoods at high tide (During high tides, tidal flooding is already affecting some of these coastal areas). Sinking ground also disrupts drainage. Subsidence can disturb the gradients of river channels and sewers, so water that should drain away instead pools in the streets (the phenomenon of land subsidence can cause the malfunctioning of the river flow system, channels and sewers, causing flooding). The city sits on a flat river delta plain crossed by 13 rivers, all of which are prone to flooding in the monsoon season (A sprawling city of more than 30 million people, Jakarta sits on a low, flat alluvial plain through which 13 rivers flow, all of which are prone to flooding during Monsoon season.). Rising sea levels therefore act on ground that is already falling, and the two effects add together.

The underlying cause is a weak public water system. Jakarta's piped-water system serves fewer than one million households, a little over a quarter of the city's total. The rest rely primarily on pumping groundwater. Local research based on figures from the national Geological Agency describes the Jakarta groundwater basin as heavily overexploited, with extraction reaching up to 40 percent against a recommended ceiling of 20 percent to prevent intrusion (the condition of the Jakarta groundwater basin which covers 3 provinces (DKI Jakarta, Banten and West Java) is currently in a very critical condition due to excessive groundwater exploitation of up to 40%, it should be a maximum of only 20% to avoid water intrusion.). Pumping has also been linked to seawater entering freshwater aquifers in both Jakarta and the Thousand Islands (groundwater extraction has been associated with both seawater intrusion and land subsidence.). Low-lying coasts, deltas and small islands elsewhere in the archipelago face similar pressures from sea-level rise, storm surges and saltwater entering aquifers, and climate change is expected to intensify floods, landslides and droughts, affecting farming, water supply and urban infrastructure.

Adaptation in Jakarta centres on the National Capital Integrated Coastal Development (NCICD) programme. It proposes a giant sea wall north of Jakarta Bay to protect the city from sea floods, with large lagoons inside the wall to buffer outflow from the 13 rivers. The concept dates to the mid-1990s and was formalised within the NCICD framework in the late 2000s (It first emerged in the mid-1990s and was later formalized within the NCICD framework in the late 2000s). Progress has been slow. The planned embankment runs about 37.3 km across ten cluster points, and about 17.1 km had been built by 2022 (The total length of the NCICD embankment path plan reaches 37.3 km that is located at 10 NCICD cluster points. As of 2022, some 17.1 km out of the total planned embankment path had been built.). Officials have attributed delays largely to budget availability, and the dike's completion target has moved from 2028 to 2030 (The NCICD dike project's completion has been pushed back from the original target of 2028 to 2030.). Other measures in planning include groundwater regulation, sea walls, relocation planning and disaster-risk management institutions. Any reduction in dependence on wells would also depend on extending piped water to households that currently rely on pumped supplies. The relocation of government functions to Nusantara is discussed in a separate section.

Strategic location and maritime routes

Indonesia lies between the Indian and Pacific oceans and between the Asian and Australian continents, which gives it control over several of the busiest passages in the region. Three chokepoints are usually cited for global trade: the Malacca–Singapore, Sunda and Lombok–Makassar straits. The Straits of Malacca and Singapore are partly administered by Malaysia and Singapore, while the Sunda and Lombok-Makassar Straits are located within the Indonesian Archipelagic Sea Lanes (ASL).

Indonesia has designated three archipelagic sea lanes under the UN Convention on the Law of the Sea. The first links the Karimata Strait, Java Sea and Sunda Strait with the Indian Ocean, the second runs from the Sulawesi Sea through the Makassar and Lombok straits, and the third connects the Pacific with the Indian Ocean through the Maluku, Seram and Banda seas before branching toward the Timor, Sawu and Arafura seas. Ships that weigh more than 230,000 deadweight tonnage (dwt) cannot pass through Malacca Strait so they must pass through the Strait of Sunda, Lombok and Makassar. The routes differ in character. The Lombok Strait is wider, deeper, and less congested, and its deep water suits supertankers. The Sunda Strait, by contrast, has limited depth and strong current, which makes it less favourable for some vessels. Traffic counts also vary by method: one estimate puts the number of transits at approximately 3,900 ships a year, while a 2023 analysis of AIS tracking data reports 77,147 trips per year.

The legal status of these routes is a matter of ongoing friction. Under the convention, vessels do not need to request permission or give prior notice to use archipelagic sea lanes, but Indonesia has a regulation that requires foreign vessels to ask permission first. Indonesia's traffic separation scheme for the Lombok Strait was carried out at the 101st session of MSC on June 2019 and became effective from June 2020. Shipping safety, navigational rights and the security concerns of major naval powers all bear on how these rules are applied.

Maritime boundary questions are most acute around the Natuna Islands, an archipelago of more than 200 islands in Riau province in the north of the country. Indonesia maintains that it has no overlapping claims with China. China's "nine dash line," which it uses to roughly demarcate its ambitions for maritime boundaries that cover most of the South China Sea, overlaps with a section of Indonesia's exclusive economic zone extending from Natuna Islands. Beijing has described the situation as "for maritime rights and interests", a formulation Jakarta rejects. The stakes include fishing grounds and offshore fields near the Natuna islands estimated to contain 46 trillion cubic feet of recoverable reserves of natural gas. A separate, unresolved overlapping exclusive economic zone (EEZ) claims with Vietnam in the North Natuna Sea also remains pending a delimitation agreement.

Fisheries management and maritime surveillance are long-standing challenges across this large sea area. To evade detection, these vessels often disable their Vessel Monitoring System or manipulate ship documentation. Monitoring is difficult in part because Indonesia has roughly half a million fishing vessels, and at least seven agencies share authority over maritime law enforcement, which can produce gaps in coverage. Since 2014 the government has taken a hard line, having sunk more than 500 illegal fishing vessels since October 2014, many with explosives. Recent efforts have focused on the Natuna Sea, where Jakarta has expanded patrols in its most contested waters, added community surveillance, and expanded international partnerships to address the threat.

Mapping, surveys and research history

Counting Indonesia's islands is a question of method as much as observation, and no single figure is settled. The number most often quoted, 17,508, appears in an official ministry listing, but the procedure behind it has not been clearly documented The most frequently cited figure today is 17,508 islands, officially listed by the Indonesian Coordinating Ministry for Maritime Affairs, but the exact methodology used to reach this number is unclear. Other surveys have produced different totals. A 2002 census by the National Institute of Aeronautics and Space, which used Landsat imagery, gave 18,307 islands. A 2007–2010 geospatial survey is cited in some references as 17,500 islands, yet the same survey's named-island total is reported separately as 13,466. The national geospatial agency has also revised its own series over time, recording 17,374 islands officially recorded in 2023, 17,024 in 2022, and 16,771 in 2020. In 2024, it confirmed the identification of 63 new islands, which had gone unnoticed because of their remote locations and were found through lidar and satellite imaging combined with field research.

The biological mapping of the archipelago owes much to Alfred Russel Wallace, who travelled through the islands for eight years, from 1854 to 1862, collecting specimens and writing on their distribution collecting biological specimens for his own research and for sale, and writing scores of scientific articles on mostly zoological subjects. His travels covered roughly 14,000 miles across about seventy expeditions. From the pattern of animal distribution he drew a boundary between animals of Asian origin and those related to Australian forms, which became known as the Wallace Line the boundary that separates the fauna of Australia from that of Asia. The line is traced through the strait between Bali and Lombok and then between Borneo and Sulawesi. Later researchers proposed revised boundaries, and the transitional zone between Wallace's line and the alternatives is known as Wallacea scholars subsequently proposed revised schemes such as Weber's Line and Lydekker's Line. The transitional zone between Wallace's Line and Lydekker's Line was defined as Wallacea. His account of the journey was published in two volumes in 1869 It was published in two volumes in 1869, delayed by Wallace's ill health and the work needed to describe the many specimens he brought home.

Systematic terrestrial mapping was carried out under the Dutch colonial administration. Survey work began in 1850, and the systematic mapping of Java took from 1850-1880, and then the mapping of the outer islands was started, a phase that continued until about 1940. The Topografische Dienst, or Netherlands Indies Topographic Survey, was founded in 1864 and placed the systematic survey on a secure institutional basis In 1864 the Topographic Survey was initiated, directly under the General Staff, and this meant putting the systematic survey started in 1850 on a secure basis. Coordination improved later, when a Central Mapping Committee was created in 1905 to bring official mapping operations under one body. The 1938 Atlas van Tropisch Nederland is often described as an early national atlas of a tropical country.

Volcanological and geological research followed a parallel course. Systematic work after 1900 was carried out by geologists of the Mining Department, and after 1920 by a Volcanological Survey Systematic research done after 1900 by geologists of the Dienst van de Mijnbouw (Mining Department) and after 1920 by the Volcanological Survey. Its bulletins recorded volcanic activity from 1927 onward Since 1927, information on volcanic activity has been recorded in Bulletins of the Netherlands East Indian Volcanological Survey (BNEIVS), the forerunner organization for today's Volcanological Survey of Indonesia (VSI). The publication programme continued through the Japanese occupation and the independence struggle The continuity of this enterprise has been maintained, remarkably, even through World War II and the post-war fight for independence. After the war, the Dutch government asked Reinout Willem van Bemmelen to assemble the existing knowledge of the archipelago's geology The Dutch government assigned to Van Bemmelen the job to recollect all information on the geology of the Indonesian Archipelago.

After independence, national mapping passed to Indonesian agencies, and the former national survey body is now the Geospatial Information Agency (BIG) Agency for Geospatial Information (BIG) previously known as National Coordinating Agency for Surveys and Mapping (Bakosurtanal). Remote sensing now underpins much of this work. Satellite data have been used for island inventories and for monitoring disaster risk, forest cover and land-use change. These tools have made it possible to detect small or remote islands that earlier fieldwork missed, but the shifts in national totals show that island counts still depend on the definitions, sensors and verification methods used.

Natural resources and economic geography

Indonesia's subsoil is rich in metals and fuels, and mining has long attracted foreign capital. Its longstanding history of mining activities has attracted significant foreign investments. As a result, the country has become a major global exporter of key minerals, including coal, nickel, tin, copper, and gold. Bauxite and manganese reserves are also significant. Its territory includes major mineral reserves of bauxite, manganese, gold, copper, tin, and coal is a major export, with the country ranked among the world's third largest coal and nickel producers.

Nickel has become the most strategically important mineral. Estimates of the country's share of world reserves vary by source: one study puts it at 42% of the world's nickel reserves, while a ministry figure for 2020 gave 52% of the global total. Output rose sharply in less than a decade, with the country's share of global extraction growing from 5% in 2015 to 50% in 2023. Most deposits lie far from the main island of Java, in Sulawesi (Central Sulawesi and South Sulawesi), the North Maluku islands and Papua. To push processing inside the country, the government banned exports of unprocessed ore in 2020, requiring that extracted raw materials be processed domestically to final goods before being allowed for global export. Laterite nickel is carbon-intensive to refine, and producing Class 1 nickel from Indonesia's laterite ore resources releases two to six times the amount of CO2 emissions as producing Class 1 nickel from sulfide deposits. The shift toward battery metals therefore links the mineral economy to the climate agenda in a direct way.

Coal and other extractive industries are concentrated in particular regions. Kalimantan, home to vast reserves of coal, gold, and other minerals, has long been a focal point of Indonesia's extractive economy. The country's coal sector also supplies domestic power and industry, which means that the coal economy remains tied to domestic energy supply even as the government promotes lower-carbon alternatives. Copper is another export pillar, and the country is also the world's third copper ore exporter.

Geothermal energy is a distinctive resource that comes directly from the volcanic arc described above. Official figures put the potential at 23,742 megawatts (MW), although a separate academic estimate reaches around 28.5 GW. Installed capacity is far lower. This is only about 10% of the geothermal potential of the country, and Indonesia's installed geothermal capacity stands at 2,744 megawatts (MW), while the United States leads with 3,937 MW. Most plants are in Java, with Java accounting for the highest installed capacity due to its proximity to major population and industrial centers. Expansion has been slow, partly because exploration is costly and risky. This makes geothermal energy a central candidate for the wider shift to renewable energy.

Economic activity is heavily concentrated in Java. In 2025, Java Island continued to play a dominant role in Indonesia's economy, contributing 56.93 percent. It was followed by Sumatra (22.22 percent), Kalimantan (8.12 percent), Sulawesi (7.22 percent), Bali and Nusa Tenggara (2.82 percent), and Maluku and Papua (2.69 percent). Java also holds most of the people, home to 56% of Indonesia's total population of 277 million. The eastern regions, which hold much of the nickel and gold, have a smaller share of output. Located far from Indonesia's economic centre, Java, these areas have historically experienced limited infrastructure and economic development. This gap shapes debates over the infrastructure needed to move minerals to port and to develop local processing.

The resource-based economy therefore links national development to several competing pressures. Export earnings depend on critical minerals, such as nickel and cobalt, [which have] an important role for electric vehicle (EV) battery production. Commodity prices shift revenue quickly, while mining, smelting and coal combustion carry environmental costs in forests, watersheds and air quality. Policy has tried to balance these pressures by requiring domestic processing, expanding geothermal and other renewable capacity, and encouraging investment in the eastern provinces. How well these measures reduce regional inequality while limiting environmental damage remains an open question in national policy.

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50. 1 TSUNAMI MORTALITY IN ACEH PROVINCE, INDONESIAunisdr.org
51. Indonesia tsunami death toll rises to 43 | Inquirer Newsnewsinfo.inquirer.net
52. Indonesia had an advanced early-warning system—but it wasn’t working when the tsunami strucktechnologyreview.com
53. Indonesia tsunami: why wasn’t there an earlier warning?theconversation.com
54. Indonesia's Early Warning System - The ASEAN Magazinetheaseanmagazine.asean.org
55. Indonesia's tsunami warning buoys downsbs.com.au
56. Broken, Stripped, and Stolen: Indonesia's Tsunami Warning System Is a Messvice.com
57. Improving Indonesia's tsunami warning systemdevex.com
58. Development of a tsunami early warning system on the coast of Palu based on maritime wireless communication - ScienceDirectsciencedirect.com
59. NHESS - The 22 December 2018 Mount Anak Krakatau volcanogenic tsunami on Sunda Strait coasts, Indonesia: tsunami and damage characteristicsnhess.copernicus.org
60. Puncak Jayaen.wikipedia.org
61. Sudirman Rangeen.wikipedia.org
62. Where is the Puncak Jaya?worldatlas.com
63. Jayawijaya Mountainsen.wikipedia.org
64. Barisan Mountainsen.wikipedia.org
65. Mount Kerincien.wikipedia.org
66. Barisan Mountainsbritannica.com
67. Indonesia Mountains: Peaks, Hiking & 3D Mapspeakvisor.com
68. Twenty Popular Volcano Hikes in Indonesiagunungbagging.com
69. Carstensz Glacieren.wikipedia.org
70. Barito Riveren.wikipedia.org
71. Daftar 10 Sungai Terpanjang di Indonesia, Kapuas hingga Musicnnindonesia.com
72. Mahakam Riveren.wikipedia.org
73. Indonesia's 10 Longest Rivers: A Complete Guidenew.chreli-abano.ge
74. 7 Deepest Rivers In Indonesia You Must Knowvoi.id
75. Indonesia Maps & Facts - World Atlasworldatlas.com
76. Lake Tobaen.wikipedia.org
77. Lake Tobaworldatlas.com
78. Lake Toba - 1,100 km2 - Facts, Map, Activitieslakepedia.com
79. Toba Caldera UNESCO Global Geopark - International Geoscience and Geoparks Programmeunesco.org
80. Indian Journal of Marine Sciences Vol. 34(1), March 2005, pp. 88-97vliz.be
81. Tag Archives: indonesiaseafdec.org
82. Java Seaen.wikipedia.org
83. Arafura Seaen.wikipedia.org
84. Banda Seaen.wikipedia.org
85. Indonesia's Rivers: A Deep Dive — A Quick Guidew3.framtida.no
86. Kapuas River (Barito River tributary)en.wikipedia.org
87. Kapuas Riveren.wikipedia.org
88. Indonesia's Climate and Precipitationindonesia.mfa.gov.ir
89. WEATHER AND CLIMATE OF INDONESIAfactsanddetails.com
90. Weather and the best time to visit Indonesiatravelfish.org
91. Best time to visit Indonesiarickshawtravel.co.uk
92. Blue Green Atlas - The Climate of Indonesiabluegreenatlas.com
93. Weather in Indonesia: seasonality, climate, temperatures by monthswiotto.com
94. Indonesia stepping up drought response as El Nino lingers - ANTARA Newsen.antaranews.com
95. Indonesia braces for possible ‘Godzilla El Niño’ as fire season escalates earlynews.mongabay.com
96. How a super-sized El Niño is fueling huge fires in Indonesiacnn.com
97. Fires are burning underground across Indonesia as El Niño strengthensearth.com
98. Peatland Fires Darken Skies in Indonesia - NASA Sciencescience.nasa.gov
99. El Niño Brought Drought and Fire to Indonesiaearthobservatory.nasa.gov
100. Environmental Research Letters (Jan 2017)doaj.org
101. Wallace Lineen.wikipedia.org
102. Fauna of Indonesiaen.wikipedia.org
103. Wallace Line - an overviewsciencedirect.com
104. What is the Wallace Line in Indonesia? - Lembeh Resort & Spalembehresort.com
105. The Dacini fruit fly fauna of Sulawesi fits Lydekker’s line but also supports Wallacea as a biogeographic region (Diptera, Tephritidae)ncbi.nlm.nih.gov
106. Indonesia - Country Profilecbd.int
107. Indonesia’s Rainforests: Biodiversity and Endangered Species - Rainforest Action Networkran.org
108. Mapping Asia Plants: Plant Diversity and a Checklist of Vascular Plants in Indonesiancbi.nlm.nih.gov
109. A bolder conservation future for Indonesia by prioritising biodiversity, carbon and unique ecosystems in Sulawesinature.com
110. The State of Indonesia’s Birds 2025burung.org
111. WILDLIFE IN INDONESIA: WALLACEA AND UNIQUE AND ENDANGERED ANIMALSfactsanddetails.com
112. Fauna & Flora's conservation work in Indonesiafauna-flora.org
113. Wallacea: a living laboratory of evolutiontheconversation.com
114. The Coral Trianglecoraltriangle.org
115. What is the Coral Triangle? Exploring the World's Marine Biodiversity Hotspot - Emperor Diversemperordivers.com
116. Environmental DNA in a Global Biodiversity Hotspot: Lessons from Coral Reef Fish Diversity Across the Indonesian Archipelagobiorxiv.org
117. Emerging marine protected areas of eastern Indonesia: Coral reef trends and priorities for management - ScienceDirectsciencedirect.com
118. Indonesia - Volcanic, Alluvial, Peatbritannica.com
119. Volcanic Soils: Their Characteristics, Management ...pdfs.semanticscholar.org
120. Kewu Plainen.wikipedia.org
121. Infiltration-Friendly Agroforestry Land Uses on Volcanic Slopes in the Rejoso Watershed, East Java, Indonesiamdpi.com
122. Indonesia pushes rice estate project despite environmental red flagsnews.mongabay.com
123. In Indonesia’s new rice plan, experts see the blueprint of an epic past failurenews.mongabay.com
124. Risk Analysis of Rice Farming at Volcano Semeru Area, ...bio-conferences.org
125. Committed carbon emissions, deforestation, and community land conversion from oil palm plantation expansion in West Kalimantan, Indonesiapnas.org
126. Shifting patterns of oil palm driven deforestation in Indonesia and implications for zero-deforestation commitments - ScienceDirectsciencedirect.com
127. Indonesia Palm Oil Industry: Overview, Analysis, Data & Statisticsindonesia-investments.com
128. From Noisy Historical Maps to Time-Series Oil Palm Mapping Without Annotation in Malaysia and Indonesia (2020-2024)arxiv.org
129. Decentralization and the environment: Assessing smallholder oil palm development in Indonesia - PMCpmc.ncbi.nlm.nih.gov
130. Closing oil palm yield gaps among Indonesian smallholders through industry schemes, pruning, weeding and improved seeds - PMCpmc.ncbi.nlm.nih.gov
131. Indigenous peoples and oil palm plantation expansion in West Kalimantan, Indonesiaworldagroforestry.org
132. Uneven participation of independent and contract smallholders in certified palm oil mill markets in Indonesianature.com
133. Enforcement of Deforestation and Peatland Conversion Moratorium - Climate Scorecardclimatescorecard.org
134. Indonesia’s Peatland Fires Spread ‘Carbon Bombs’ Across 4.5 Million Hectares - Time Newstime.news
135. Indonesia battling wildfires as smoke haze spreads as far as the Philippines - ABC Newsabc.net.au
136. Indonesia Wildfires Mapcurrentwildfires.com
137. Major atmospheric emissions from peat fires in Southeast Asia during non-drought years: evidence from the 2013 Sumatran firesncbi.nlm.nih.gov
138. Fire carbon emissions over maritime southeast Asia in 2015 largest since 1997ncbi.nlm.nih.gov
139. How haze from Indonesian fires impacts Southeast Asia - The Japan Timesjapantimes.co.jp
140. Water Table Collapse Is Driving Indonesia's Peatland Fires, Researchers Warn Amid Record Burnstechtimes.com
141. Residents struggle amid haze in Indonesia, yet government fails to grasp the root cause of peatland fires - Greenpeace Southeast Asiagreenpeace.org
142. Indonesia’s forest moratoriumnews.mongabay.com
143. Indonesia forest-clearing ban is made permanent, but labeled ‘propaganda’news.mongabay.com
144. Indonesian Moratoria: Loopholes, Lack of Sanctions Fail to Stop Palm Oil-Linked Deforestation - Chain Reaction Researchchainreactionresearch.com
145. Six years of moratorium: How much of Indonesia’s forests have been protected? - Greenpeace Southeast Asiagreenpeace.org
146. Indonesia - Population and Demography Country Profileourworldindata.org
147. POPULATION OF INDONESIA: DEMOGRAPHICS, GROWTH, TRENDS, IMPACTSfactsanddetails.com
148. Indonesia Population & Demographics: Analysis of Size, Growth & Diversityindonesia-investments.com
149. Urbanization and urban development patterns - Sat, May 12, 2012 - The Jakarta Postthejakartapost.com
150. (PDF) Transmigration in Indonesia: Lessons from Its Environmental and Social Impactsresearchgate.net
151. TRANSMIGRATION IN INDONESIA: HISTORY, SETTLERS, PROBLEMSfactsanddetails.com
152. Unity in Diversity? Ethnicity, Migration, and Nation Building in Indonesia∗bu.edu
153. Transmigration programen.wikipedia.org
154. Indonesian Transmigration and the Crisis of Development, 1968–1985academic.oup.com
155. Designing more effective resettlement programs: Lessons from transmigration in Indonesiavoxdev.org
156. Will Indonesia Repeat the History of Population Mobility in Borneo? - Modern Diplomacymoderndiplomacy.eu
157. Jakarta metropolitan areaen.wikipedia.org
158. URBAN LIFE IN INDONESIA: GROWTH, PROBLEMS, JAKARTA, NOW THE WORLD'S BIGGEST CITYfactsanddetails.com
159. Bandungglobalfuturecities.org
160. List of metropolitan areas in Indonesiaen.wikipedia.org
161. Impact of continuous Jakarta megacity urban expansion on the formation of the Jakarta-Bandung conurbation over the rice farm regions - ScienceDirectsciencedirect.com
162. Constitutional Court Confirms Jakarta Still Indonesia's Capital, Not Nusantarajakartaglobe.id
163. Nusantara Set as Indonesia's Political Capital in 2028 Under Prabowo's Regulation - News En.tempo.coen.tempo.co
164. Full article: Indonesia’s New Capital City: Public Funding and Public Supporttandfonline.com
165. House Commission II reaffirms support for Nusantara’s development - Quick Dispatch - The Jakarta Postthejakartapost.com
166. Indonesia's Nusantara Capital: What Is Known So Far - News En.tempo.coen.tempo.co
167. Indonesia - Capitalworldcapitals.org
168. Court ruling raises further questions over future of Indonesia's Nusantarathestar.com.my
169. Jakarta Remains Capital: OIKN Response to Court Ruling - News En.tempo.coen.tempo.co
170. Nusantara, Future Capital of Indonesiaearthdata.nasa.gov
171. Indonesia's new capital city Nusantara downgraded to political capitaldezeen.com
172. Nusantaraen.wikipedia.org
173. Nusantara: Indonesia's $32 Billion Capital Move Hits a Crossroadslinos.ai
174. Halting Jakarta’s Land Subsidence for Climate Resilience ｜ Adaptation Database ｜ Asia-Pacific Climate Change Adaptation Information Platform (AP-PLAT)ap-plat.nies.go.jp
175. (PDF) Land subsidence of Jakarta (Indonesia) and its relation with urban developmentresearchgate.net
176. (PDF) Land subsidence characteristics of the Jakarta basin (Indonesia) and its relation with groundwater extraction and sea level riseresearchgate.net
177. Indonesia's giant capital city is sinking. Can the government's plan save it?nationalgeographic.com
178. LAND SUBSIDENCE AND GEOTECHNICAL IMPACT OF ...e-journal.trisakti.ac.id
179. Sinking Cityunfccc.int
180. Giant Sea Wall Jakartaen.wikipedia.org
181. Indonesia’s giant sea wall takes shape as climate pressures mountindonesiabusinesspost.com
182. Jakarta finalizing giant sea wall concept - ANTARA Newsen.antaranews.com
183. Jakarta's Giant Sea Wall Project Delayed Over Budget Constraints - News En.tempo.coen.tempo.co
184. The US Rebalancing to Asia: Indonesia's Maritime Dilemmapacforum.org
185. Indonesian Traffic Separation Schemes (TSS): Aatlantis-press.com
186. Chapter 4 Sea lane security in the selected EAS countries November 2016eria.org
187. Full article: Legal Analysis of the Establishment of Exclusion Zones for Submarines in Indonesia’s Archipelagic Sea Lanestandfonline.com
188. Where do ships go when they cannot pass through Malacca? The story of the Lombok and Sunda Straits｜🏖️うみ🏖️海事代理士note.com
189. Indonesia president visits islands also claimed by China | Inquirer Newsnewsinfo.inquirer.net
190. Indonesian leader stands up to China, visits isles off clash sitenewsinfo.inquirer.net
191. China’s Natuna Island Fishing Dispute with Indonesia (Chapter 6) - China's Naval Operations in the South China Seacambridge.org
192. Managing the Vietnam–Indonesia North Natuna Sea disputeeastasiaforum.org
193. IUU Fishing: A Devastating Threat to Indonesia and the Worldfairobserver.com
194. Capacity building to manage illegal fishing in Indonesia - CSIROcsiro.au
195. To Secure the Natuna Sea, Indonesia Needs More Than New Shipsthediplomat.com
196. Natuna Islands: Indonesia says no 'overlapping' South China Sea claims with China - ABC Newsabc.net.au
197. Indonesia’s 13558 islands: A new census from space and a first step towards a One Map for Small Islands Policy - ScienceDirectsciencedirect.com
198. Indonesia's geospatial agency identifies 63 new islands in 2024 - ANTARA Newsen.antaranews.com
199. Alfred Russel Wallacebritannica.com
200. Wallace Line_Baiduwikibaike.baidu.com
201. The Malay Archipelagoen.wikipedia.org
202. COLONIAL CARTOGRAPHY OF THE NETHERLANDS EAST INDIES 1816-1942 Ferjan Ormelingicaci.org
203. Artº: History of the volcanology in the former Netherlands East Indies (1983) - M. Neumann van Padangscribd.com
204. Historical eruptions of Merapi Volcano, Central Java, Indonesia, 1768–1998 - ScienceDirectsciencedirect.com
205. Reinout Willem van Bemmelenen.wikipedia.org
206. The Analysis of Geospatial Information for Validating Some Numbers of Islands in Indonesiajournal.ugm.ac.id
207. Alfred Russel Wallace's Expeditionsebsco.com
208. Advancing from Nickel Mining to Downstream Processing Lessons Learned from theafdb.org
209. The Prospects of Indonesia's Nickel Boom Amidst a ...ifri.org
210. Indonesia Country Commercial Guidetrade.gov
211. Map of the distribution of Indonesia's nickel resources and reserves,...researchgate.net
212. Policy Insight March 2026 How Indonesia’s ban on raw nickel exportscetex.org
213. Indonesia’s coal burning hits record high — and ‘green’ nickel is largely whynews.mongabay.com
214. Illuminating the future with geothermal power - ANTARA Newsen.antaranews.com
215. A strategic analysis of geothermal energy for sustainable energy transition: Case study from Indonesia - ScienceDirectsciencedirect.com
216. Indonesian Government sets direction for geothermal growth at IIGCE 2025thinkgeoenergy.com
217. Indonesia ranks second globally in geothermal energy capacity - ANTARA Newsen.antaranews.com
218. Investing in Indonesia’s Geothermal Energy Sectorcekindo.com
219. Profile Ekonomi Provinsi - Kadin Indonesiakadin.id
220. Java, Palm Oil, Nickel and Bali: The Engines of Indonesia’s Economyandamanpartners.com
221. Indonesian economy still concentrated on Java Island: BPS Head - ANTARA Newsen.antaranews.com