The Sumatran lowland rain forests

ecoregion An ecoregion (ecological region) is an ecological and geographic area that exists on multiple different levels, defined by type, quality, and quantity of environmental resources. Ecoregions cover relatively large areas of land or water, and c ...

(WWF ID: IM0158) covers the lowland forests running the length of the island of

Sumatra Sumatra () is one of the Sunda Islands of western Indonesia. It is the largest island that is fully within Indonesian territory, as well as the list of islands by area, sixth-largest island in the world at 482,286.55 km2 (182,812 mi. ...

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...

. The region is one of exceptionally high biodiversity, similar to

Borneo Borneo () is the List of islands by area, third-largest island in the world, with an area of , and population of 23,053,723 (2020 national censuses). Situated at the geographic centre of Maritime Southeast Asia, it is one of the Greater Sunda ...

and

New Guinea New Guinea (; Hiri Motu: ''Niu Gini''; , fossilized , also known as Papua or historically ) is the List of islands by area, world's second-largest island, with an area of . Located in Melanesia in the southwestern Pacific Ocean, the island is ...

islands. Many endangered mammals species (including the Sumatran rhinoceros and the Lar gibbon) are present, and over 450 species of birds have been found in the region. In recent years,

illegal logging Illegal logging is the harvest, transportation, purchase, or sale of timber in violation of laws. The harvesting procedure itself may be illegal, including using corrupt means to gain access to forests; extraction without permission, or from a p ...

and human encroachment have put great strain on this ecoregion.

Location and description

The ecoregion runs for 1,600 km down the northeast and southwest sides of the

Barisan Mountains The Bukit Barisan or the Barisan Mountains are a mountain range on the western side of Sumatra, Indonesia, covering nearly 1,700 km (1,050 mi) from the north to the south of the island. The Bukit Barisan range consists primarily of volca ...

on the island of Sumatra. The ecoregion thus surrounds the higher elevation Sumatran ''montane'' rain forests ecoregion. The lowlands rainforest is at an average elevation of , and a maximum of . Also in this region are the islands of

Simeulue Simeulue is an island of Indonesia, off the west coast of Sumatra. It covers an area of 1,754 square kilometre (677 square miles), including minor offshore islands. It had a population of 80,674 at the 2010 census and 92,865 at the 2020 census ...

Nias Nias (, Nias: ''Tanö Niha'') is an island located off the western coast of Sumatra, Indonesia. Nias is also the name of the archipelago () of which the island is the centre, but also includes the Batu Islands to the southeast and the small ...

(both about 150 km off the west coast), and

Bangka Island Bangka is an island lying east of Sumatra, Indonesia. It is administered under the province of the Bangka Belitung Islands, being one of its namesakes alongside the smaller island of Belitung across the Gaspar Strait. The 9th largest island in ...

off the east coast.

Climate

This ecoregion has a

tropical rainforest climate A tropical rainforest climate or equatorial climate is a tropical climate sub-type usually found within 10 to 15 degrees latitude of the equator. There are some other areas at higher latitudes, such as the coast of southeast Florida, United States ...

(

Köppen Köppen is a German surname. Notable people with the surname include: * Bernd Köppen (1951–2014), German pianist and composer * Carl Köppen (1833-1907), German military advisor in Meiji era Japan * Edlef Köppen (1893–1939), German author ...

: ''Af''). This climate is characterized as hot, humid, and having at least 60 mm of precipitation every month. The lowland rain forests on the west side of the Barisan Mountains are wetter (6,000 mm/year) than those on the east side (2,500+ mm/year).

Flora and fauna

The characteristics trees in the lowland rain forest are those of family Dipterocarpaceae (Greek: di = two, pteron = wing and karpos = fruit). On Sumatra, 111 species of these trees have been recorded, six of which are endemic. These trees in the canopy can reach 90 meters in height. The dipterocarps in the understory are joined by smaller trees of the 'peacock flower' family (

Caesalpinioideae Caesalpinioideae is a botanical name at the rank of subfamily, placed in the large family Fabaceae or Leguminosae. Its name is formed from the generic name '' Caesalpinia''. It is known also as the peacock flower subfamily. The Caesalpinioideae a ...

). Other trees include torchwood trees (

Burseraceae The Burseraceae are a moderate-sized family of 17-19 genera and about 540 species of woody flowering plants. The actual numbers given in taxonomic sources differ according to taxonomic revision at the time of writing. The Burseraceae are also ...

), evergreens of the family

Sapotaceae 240px, '' Madhuca longifolia'' var. ''latifolia'' in Narsapur, Medak district, India The Sapotaceae are a family of flowering plants belonging to the order (biology)">order Ericales">family (biology)">family of flowering plants belonging to th ...

, member of the coffee family (

Rubiaceae Rubiaceae () is a family (biology), family of flowering plants, commonly known as the coffee, madder, or bedstraw family. It consists of terrestrial trees, shrubs, lianas, or herbs that are recognizable by simple, opposite leaves with Petiole ( ...

), members of the soursop family (

Annonaceae The Annonaceae are a Family (biology), family of flowering plants consisting of trees, shrubs, or rarely lianas commonly known as the custard apple family or soursop family. With 108 accepted genera and about 2400 known species, it is the largest ...

), laurels (

Lauraceae Lauraceae, or the laurels, is a plant Family (biology), family that includes the bay laurel, true laurel and its closest relatives. This family comprises about 2850 known species in about 45 genus (biology), genera worldwide. They are dicotyled ...

), and the nutmeg family (

Myristicaceae The Myristicaceae are a family of flowering plants native to Africa, Asia, Pacific islands, and the Americas and has been recognized by most taxonomists. It is sometimes called the "nutmeg family", after its most famous member, '' Myristica fragr ...

). Trees of the mulberry family (

Moraceae Moraceae is a family of flowering plants comprising about 48 genera and over 1100 species, and is commonly known as the mulberry or fig family. Most are widespread in tropical and subtropical regions, less so in temperate climates; however, their ...

) are also common, with over 100 species.

Epiphytes An epiphyte is a plant or plant-like organism that grows on the surface of another plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating around it. The plants on which epiphyt ...

(plants that grow on the surface of others and gather moisture from the atmosphere or surroundings) are common. There is little ground vegetation, mostly saplings of canopy trees. The soils are commonly

Podzol Podzols, also known as podosols, spodosols, or espodossolos, are the typical soils of coniferous or boreal forests and also the typical soils of eucalypt forests and heathlands in southern Australia. In Western Europe, podzols develop on heathlan ...

s in the lowland rain forest. Mammals and birds are very diverse, with species similar to

and the Malaysian Peninsula as all three landmasses were connected in the last ice age. Mammals of conservation interest include the endangered

Asian elephant The Asian elephant (''Elephas maximus''), also known as the Asiatic elephant, is the only living ''Elephas'' species. It is the largest living land animal in Asia and the second largest living Elephantidae, elephantid in the world. It is char ...

''(Elephas maximus)'', the endangered Lar gibbon ''(Hylobates lar)'' (the Sumatran rain forests contain many species of primates), the

endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching, inv ...

Malayan tapir The Malayan tapir (''Tapirus indicus''), also called Asian tapir, Asiatic tapir, oriental tapir, Indian tapir, piebald tapir, or black-and-white tapir, is the only living tapir species outside of the Americas. It is native to Southeast Asia from ...

''(Tapirus indicus)'', and the

critically endangered An IUCN Red List critically endangered (CR or sometimes CE) species is one that has been categorized by the International Union for Conservation of Nature as facing an extremely high risk of extinction in the wild. As of December 2023, of t ...

Sumatran rhinoceros The Sumatran rhinoceros (''Dicerorhinus sumatrensis''), also known as the Sumatran rhino, hairy rhinoceros or Asian two-horned rhinoceros, is a rare member of the family Rhinocerotidae and one of five extant species of rhinoceros; it is the o ...

''(Dicerorhinus sumatrensis)''. Over 450 species of birds have been recorded. Many endemic species are found in the

biodiversity hotspot A biodiversity hotspot is a ecoregion, biogeographic region with significant levels of biodiversity that is threatened by human habitation. Norman Myers wrote about the concept in two articles in ''The Environmentalist'' in 1988 and 1990, after ...

around

Lake Toba Lake Toba (, Toba Batak: ᯖᯀᯬ ᯖᯬᯅ; romanized: ''Tao Toba'') is a large natural lake in North Sumatra, Indonesia, occupying the caldera of the Toba supervolcano. The lake is located in the middle of the northern part of the island of ...

, located in the caldera of a

supervolcano A supervolcano is a volcano that has had an eruption with a volcanic explosivity index (VEI) of 8, the largest recorded value on the index. This means the volume of deposits for such an eruption is greater than . Supervolcanoes occur whe ...

Protected areas

About 7% of the ecoregion is under some form of official protection. The protected areas include: * Mount Leuser National Park *

Bukit Barisan Selatan National Park Bukit Barisan Selatan National Park is a national park in Sumatra, Indonesia. The park located along the Bukit Barisan mountain range, has a total area of 3,568 km2, and spans three provinces: Lampung, Bengkulu, and South Sumatra. Together ...

* Kerinci Seblat National Park * Bukit Tigapuluh National Park * Tesso Nilo National Park * Bukit Duabelas National Park

References

{{reflist Indomalayan ecoregions Ecoregions of Indonesia Tropical and subtropical moist broadleaf forests Ecoregions of Malesia