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- $Unique_ID{bob00208}
- $Pretitle{}
- $Title{Indonesia
- Chapter 2A. The Society and Its Environment}
- $Subtitle{}
- $Author{Riga Adiwoso-Suprapto}
- $Affiliation{HQ, Department of the Army}
- $Subject{islands
- java
- sea
- sumatra
- indonesia
- island
- indonesian
- area
- sulawesi
- western
- see
- pictures
- see
- figures
- }
- $Date{1982}
- $Log{}
- Title: Indonesia
- Book: Indonesia, A Country Study
- Author: Riga Adiwoso-Suprapto
- Affiliation: HQ, Department of the Army
- Date: 1982
-
- Chapter 2A. The Society and Its Environment
-
- Indonesians call their country "Our Lands and Waters" (Tanah Air Kita),
- an appropriate name for a country of islands whose water surface area is
- greater than its land area. The sea is an important part of Indonesian life,
- providing the main share of protein in the daily diet and functioning both as
- a pathway for communication and as a cultural barrier. The difficulty of
- reaching the interior of many islands has served to foster social, cultural,
- and economic isolation among the approximately 300 ethnic groups. The
- archipelagic nature of the country-incorporating some 13,000 islands-has
- provided naturally discrete regions where ethnic groups have been able to
- develop a cultural core of their own, with varying degrees of input from
- outside.
-
- Indonesia is known to be a meeting ground of cultural forces. Its
- history must be interpreted in terms of the importation and adaptation of
- ideas and philosophies from India, the Islamic world, China, and the West. The
- complexity of modern Indonesian society can only be explained, however, in the
- light of both indigenous foundations and foreign influences. Foreign
- influences figured significantly in the shaping of Indonesian society, but to
- seek to explain its evolution solely in terms of alien inspiration would be
- wholly misleading. Belief in the underlying importance of harmony and
- consensus and the value of maintaining man and nature in equilibrium have
- enabled Indonesia to absorb outside influences without being absorbed itself.
-
- In the 1980s modern Indonesian society was still in transition. It had
- absorbed those Western influences it felt were necessary to gain international
- recognition and promote economic development; at the same time the government
- was seeking to increase national consciousness and pride. But in its attempt,
- the government had to confront a multiplicity of diverse ethnic traditions.
- Those diverse traditions reflected a complex mosaic of self-conscious ethnic
- groups distinguished by custom, ecological adaptation, religious belief and
- practices, language and social organization.
-
- Although the government strives for the nationalist ideal of a homogenous
- society and encourages the people to regard themselves as Indonesians,
- feelings of ethnic distinctiveness remain strong; at the same time,
- identification with an ethnic group is not felt to be incompatible with
- loyalty to the Indonesian nation. The foundation for national consciousness
- was laid through the experience of Dutch colonization and Japanese occupation
- shared by the various ethnic groups.
-
- The majority of Indonesians are rural inhabitants, attached to the
- traditional cultural values of the ethnic groups to which they belong. The
- rural inhabitants present themselves as an undifferentiated group, solidly
- loyal to each other; nonetheless, the social organization has continued to be
- based on a centuries-old division between gentry and commoners. The
- introduction of modern technological knowledge into the rural areas has
- caused rapid change in social values, often producing a materialistic outlook
- incompatible with a traditional orientation.
-
- In the 1980s social organization in the cities and towns was based on two
- variables: the degree to which an urban inhabitant maintained an ethnic
- heritage and the amount of Western influence exhibited in a life-style. At the
- apex of urban society was a tiny segment of the elite stratum that preserved
- only a minimal amount of its ethnic legacy, being oriented instead toward a
- metropolitan cultural tradition modeled on that of the West. An important
- characteristic of this metropolitan culture was its use of the Indonesian
- language in literature, popular music, films, and everyday communication. The
- rest of the elite stratum was also oriented toward metropolitan culture but
- exhibited a larger degree of adherence to its ethnic heritage. Below the elite
- stratum were middle and lower classes, whose members were mostly bicultural;
- they retained features of their ethnic culture for certain domains in their
- life, while adopting to metropolitan culture in others.
-
- Upward mobility in urban society was attained through a combination of
- family connections, education, military background, and personal experience.
- Yet, for many in the middle and lower classes, such mobility was hindered by
- the steady increase in the labor force, which had resulted in severe
- unemployment and underemployment problems. To alleviate the impact of these
- conditions in both urban and rural areas, the government emphasized employment
- expansion through agricultural development programs and efforts to promote
- industrial growth.
-
- Another major problem was the uneven distribution of the population.
- Java, comprising only 6.9 percent of the total land area, had almost 65
- percent of the population. In the early 1980s the government was encouraging
- voluntary migration to other, less densely populated islands, under what was
- officially termed transmigration. The development plan Repelita III allocated
- some Rp 109 trillion (for the value of the rupiah-see Glossary) to move
- approximately 2.5 million people. The goal was highly optimistic, given the
- difficulties in establishing basic community infrastructure and roads, coupled
- with the harshness of the terrain in resettlement areas.
-
- In the urban centers the deep cleavage between the elite and the poorest
- groups in society gave rise to such problems as prostitution, crime and
- violence, and juvenile delinquency. Many rural inhabitants moved to the cities
- with the hope of attaining a better life or earning enough money to send their
- extended families in the countryside. In the cities they often failed to find
- adequate employment, however, resulting in frustration and disappointment.
- Against these frustrations inherent in modernization, kinship ties provided
- security and economic support.
-
- The family-generally an extended one-was the central relationship in the
- lives of most Indonesians. Personal welfare, as well as care for the
- handicapped, was considered a family matter. Family networks also provided
- employment opportunities for members. Although there was no specific ideal
- family size, in general, children were desired as insurance for care in the
- parents' old age. At every level of society, kinship and marriage reinforced
- economic and social alliances.
-
- Geography and Population
-
- Indonesia stretches some 5,120 kilometers from east to west across the
- equator, the greater part being below the equator (see fig. 1). It is the
- largest archipelagic nation in the world, encompassing 13,677 islands and
- having a land and sea area of 4.8 million square kilometers, of which only
- approximately 1.9 million square kilometers are land. Laid over a map of the
- United States, the archipelago would considerably overlap New York and San
- Francisco.
-
- Its geographic location at one of the world's major crossroads has made
- Indonesia strategically important in the context of regional and superpower
- rivalries. The country forms a natural barrier separating the Indian Ocean,
- the South China Sea, and the Pacific Ocean. With Malaysia, it commands the
- Strait of Malacca-one of the world's busiest waterways. Through its islands
- also pass other important sea routes from the Suez Canal and the Persian Gulf
- to China, Japan, and North and South America, including the passages of Selat
- Sunda, Selat Lombok, and the Makassar Strait. Travel between Australia and
- East Asia, as well as to North America, must also traverse the archipelago.
-
- The country incorporates the territory of the former Netherlands Indies
- and Portuguese Timor. It shares land borders with Malaysia on the northern
- part of the island of Borneo and with Papua New Guinea on the island of New
- Guinea. Indonesia is separated from Malaysia by the Strait of Malacca, from
- the Asian continent by the South China Sea, from the Philippines by the
- Celebes Sea, and from Australia by the Timor Sea and the Arafura Sea.
-
- The government considers the issues of territorial waters and sea limits
- to be important elements in the protection of national security and natural
- resources, for example, in the control of pollution and oil spills. It
- maintains that, as an archipelagic nation, Indonesia's territorial waters
- include all sea areas within a maritime belt of 12 nautical miles drawn from
- a baseline connecting the outer perimeter of its islands. All straits, bays,
- and waters within the baseline are considered inland seas. As for fish
- resources and the seabed area, the government claims control over those areas
- within 200 nautical miles from the baseline, a position that reflects the
- increased economic importance of offshore petroleum and other resources. In
- the 1973-81 period Indonesia concluded a series of agreements regarding
- continental shelf boundaries with Malaysia, Thailand, India, Papua New Guinea,
- and Australia. As of late 1982 its claims to sections of the South China Sea
- north of the Natuna Islands overlapped those declared by the Socialist
- Republic of Vietnam (Vietnam) in the late 1970s.
-
- Since the early 1970s Indonesia and Malaysia have challenged the
- international status of the Strait of Malacca, claiming instead that these
- waters are part of the territorial waters of both nations. They have asserted
- that access to the strait can only be gained by other nations under the right
- of innocent passage and have requested that all foreign warships notify both
- governments before moving through those waters. The United States and several
- other nations do not accept these claims, however, and maintain that the
- Strait of Malacca is an international waterway and therefore open to all ships
- under the right of free transit.
-
- Although there is no dispute about the territorial boundaries between
- Indonesia and the Malaysian provinces of Sabah and Sarawak on the island of
- Borneo, in the early 1960s Indonesia strenuously objected to the incorporation
- of both into Malaysia. Since that time, however, the occasional territorial
- disputes of the boundary were related to local tribal matters rather than to
- geographical boundary disputes.
-
- Western New Guinea was brought under Indonesian administration in 1963
- through the United Nations-sponsored Act of Free Choice, after a lengthy
- confrontation with the Dutch government. The Portuguese part of the island of
- Timor became a province of Indonesia in July 1976, after Indonesian
- "volunteers" landed in the territory to counteract what Indonesia saw as a
- growing threat to its own security from a leftist, anti-Indonesian political
- group that was gaining ascendancy (see The New Order under Soeharto, ch. 1).
-
- Topography
-
- The Indonesian archipelago has a highly complex geological history, which
- has resulted in the nation's volcanic soil conditions, numerous mountain
- systems, and varied flora and fauna. The nation comprises three separate
- geologic areas. In the west the main islands of Java, Bali, and Sumatra, with
- Indonesian Borneo (Kalimantan) and the lesser islands between them, rise from
- the submerged Sunda Shelf, which is considered a continuation of the Eurasian
- continent. In the east the island of New Guinea (the western portion of which
- is the Indonesian province of Irian Jaya) and a few associated island groups
- are exposed parts of another submerged platform that is part of the Australian
- continent. Between these two shelves in a sea area of great depth lie several
- islands, including Sulawesi and the Malukus. A geologic formation outside the
- archipelago, the Java Trench, has also affected the nation's topography. Lying
- to the west of Sumatra and to the south of Java at the easternmost extent of
- the Indian Ocean, the deep marine trench is a very active seismic region, its
- deepest point off the coast of Java descending to a depth of 7,317 meters.
- According to the theory of continental drift, the Java Trench marks the line
- where the Indian continental plate plunges under the Eurasian plate. Their
- intersection has produced the ridge on the several islands off the coast of
- Sumatra and the mountain systems that run from Sumatra in the west to the
- atolls of the Banda Seas in the east.
-
- The three geologic areas correspond to three sea regions, one of which
- encompasses the Java Sea, the Strait of Malacca, and the southern part of the
- South China Sea. The shallow waters of the Java Sea, a major national and
- international trade artery, are less than 185 meters deep. They are free from
- strong currents and are protected from the heavy storms and typhoons that
- usually trouble the waters north of the island of Borneo or the Philippines.
-
- The second region, the Sahul Shelf in the easternmost part of the
- archipelago, presents a similar picture. Most of the part of this shelf within
- the Indonesian territory is covered by the Arafura sea, which has an average
- depth of less than 200 meters. Its waters, too, are calm, but the sea is not
- as busy as the Java Sea. It has never been of great significance in either
- international or internal trade, and most activities are limited to small
- fisheries.
-
- The third maritime region, encompassing the Banda and Flores seas, lies
- between the Sunda and Sahul shelves. Here the average depth is 10 times
- greater than in the other two regions. The floor of the Banda Sea presents a
- most astonishing terrain of uplands and lowlands; the Lucipara Islands group,
- among others, rises above the surface to indicate the presence of submerged
- mountain ridges. Earth movements are still taking place in this region,
- causing tidal waves with extremely complex ocean currents. Local fishermen
- avoid venturing too far from land. The presence of coral reefs and atolls is a
- further hazard to seafarers.
-
- Besides its complex sea condition, Indonesia is also a highly volcanic
- region. There are two main mountain systems intersecting in Sulawesi and
- Halmahera, one of the Maluku Islands. The first system consists of two
- parallel ridges running through Sumatra, Java, Bali, and Timor, curving
- sharply to Ceram and Buru. The second runs through the Philippines into
- eastern Indonesia. The complexity of the mountain structures and the highly
- varied elevations throughout Indonesia affect climatic conditions and the
- humidity of the region.
-
- It is estimated that over 100 peaks are still active volcanoes. They are
- located along the more recently formed system of mountains that passes through
- Sumatra, Java, and the Lesser Sunda Islands. Almost all are of the composite
- type wherein lava escapes not only through a central cone but also through
- cracks in the side, giving rise to the formation of parasitic craters. Of the
- 128 active volcanoes in different parts of Indonesia, 70 have erupted. In 1883
- Krakatau, for several centuries a dormant volcano, suddenly erupted, and the
- explosion could be heard as far as Australia. The volcano is still active.
- Volcanic eruptions have led to much destruction, as was the case of the
- eruption of Mount Agung in Bali in 1963 and of Mount Galunggung in Java in
- mid-1982; but offsetting this, volcanic ash has fertilized the soil (assuming
- the ash is not acidic), and the slopes of the volcanoes, normally composed of
- rocks that retain water, form natural underground reservoirs. The height of
- the volcanic peaks forms a barrier to rain-bearing winds, and precipitation
- falls in greater amounts on the windward side.
-
- Like other volcanic zones, Indonesia suffers from earthquakes. The
- aftereffects, in the form of tidal waves, are often more disastrous than the
- earthquakes themselves. Sulawesi and the surrounding area suffer frequently
- from earthquakes of varying magnitude, but fortunately most are centered not
- on land but under the surrounding seas at considerable depth.
-
- Coastal plains on many islands are being broadened by the process of
- erosion and siltation that has continued over the centuries. Every year the
- rivers bring down large quantities of silt to be deposited on the lowlands. It
- is estimated that the eastern coast of Sumatra is being extended eastward at a
- rate of 91 meters per year, while the northern coast of Java is increasing by
- 2.7 meters per year. Despite the rapid siltation taking place, the rivers of
- the large islands, which are really flooded river valleys, have comparatively
- wide estuaries. Excessive siltation is responsible for the absence of good
- deep harbors on the coasts of the major islands facing the Strait of Malacca,
- the Java Sea, and the South China Sea. Dredging has to be carried out
- constantly to keep them deep enough for navigation.
-
- Geographic Regions
-
- The Indonesian islands are commonly divided into four groups. The first
- of these is composed of the larger islands, formerly known collectively as the
- great Sunda complex, consisting of Sumatra, Java, Borneo, and Sulawesi. The
- second is made up of the islands east of Java from Bali to Timor, known as the
- Little or Lesser Sunda Islands. The Maluku Islands between Sulawesi and the
- Lesser Sunda Islands comprise the third group; and the fourth is Irian Jaya,
- the western part of the island of New Guinea.
-
- The Larger Islands
-
- Much of the eastern coast of Sumatra consists of badly drained swampy
- lands, where thick layers of peat have formed in many places. The swamps are
- as much a barrier to communication and roadbuilding as are the island's
- interior mountains. Only one limited area-between the Tamiang River and Asahan
- River on the northeastern coast of Sumatra-is relatively free from swamps.
- Here lie well-drained plains, whose undulating surfaces and fertile alluvial
- soil make them ideal for agriculture, particularly for rubber cultivation.
-
- In every way, the western coast of Sumatra, delineated by the Barisan
- Mountains, differs from the eastern coast. The coastal plain along western
- Sumatra is too narrow to permit extensive settlement, and the rivers that
- cross it are short and flow swiftly. The only areas of real value for
- agriculture are the coastal plain of Aceh and the narrow strip of land north
- of Padang, the only important commercial center on the western coast. South of
- Padang, heavy surf and the presence of coral reefs discourage shipping.
- Vessels tend to avoid ports of western Sumatra and instead pass through Selat
- Sunda to sail safely into the Java and South China seas.
-
- The backbone of the Barisan Mountains runs from the northern tip of
- Sumatra to the south and has been a great barrier to east-west communication.
- All the island's large rivers originate within it, but they do not create
- passes, as in Java. Communication routes tend to run lengthwise along the
- mountains rather than across them from west to east.
-
- From an economic standpoint Sumatra is most important to Indonesia for
- its mineral resources. The country's largest oil basin, the Minas field in
- central Sumatra, yields crude oil of the light and low sulfur type. Large
- deposits of natural gas were found in the Arun field of the Special Territory
- of Aceh in 1971 and 1972 (see Industry, ch. 3). Tin, which along with crude
- oil constitutes Indonesia's prime earner of foreign exchange, is another
- product of the region. It is found on the islands of Bangka, Billiton, Lingga,
- and Singkep. Bauxite is found in the Riau Province.
-
- Java bears little resemblance to Sumatra, although it is structurally a
- continuation of Sumatra, with the same mountain systems. Its mountains in no
- way impede communication or settlement; however, they have been eroded almost
- to base level, and the major roads and railroads simply skirt the foothills of
- the volcanoes. Nor have extensive, swampy, water-logged plains built up as on
- Sumatra. Although in past centuries ships could travel quite a distance
- inland, neither the rivers of Java nor those of Sumatra are much used today
- for navigation. On Java the terrain makes road construction quite easy.
-
- Java is the most heavily populated island, having an average density of
- about 700 persons per square kilometer. From the rice farmer's perspective the
- superior productivity of Java as a volcanic region outweighs the risk of
- living there, although villages and large crop areas have been burned badly by
- volcanic eruptions from time to time. Further, the main agricultural activity
- in Java is wet-rice cultivation, which requires less land than do other kinds
- of cultivation. Teak on the northern part of the island is an important
- resource. Drilling of oil also occurs offshore from the northern coast.
-
- In the Indonesian portion of Borneo, communication between the interior
- and the coastal people is difficult owing to ecological conditions. Rivers
- have served, and in the early 1980s continued to serve, as transport routes;
- however, the silt-laden rivers and their countless tributaries, having only
- slight gradients, deposit sediment on the lowland in great volume, forming
- wide swamps and sandbars across the estuaries, which inhibit navigation by
- large vessels. Floods occurring every wet season are an additional handicap,
- making travel hazardous; in the dry season the water level falls considerably,
- also hindering navigation. In the upper reaches, rapid waterfalls present
- another problem. Road construction is impossible along the marshy coastline,
- and it is not economical to build roads through the difficult uplands.
-
- Attempts have been made to farm the wetlands that are subject to seasonal
- flooding, provided that they are free of saltwater contamination; however,
- only moderate success has been achieved. The cultivators need to have good
- knowledge of the rising and receding patterns of the river because planting
- must be done just before the river overflows its banks.
-
- Kalimantan is Indonesia's principal source of tropical hardwoods and
- timber. In many areas deforestation of primary growth has left the island with
- secondary jungle. The soil suffers from extensive leaching and accompanying
- erosion owing to inappropriate farming methods, and reforestation is not
- practiced. The eastern portion of the island is a major source of natural gas,
- second only to Arun. The Badak field is a major site, while offshore drilling
- takes place in the southern and western portions of the island. Other
- resources are nickel, copper, bauxite, and coal, found along the Mahakam
- River.
-
- Unlike the other major islands, Sulawesi has no swamps. It has a steep
- interior terrain and a high percentage of elevated land; it has no wide
- coastal plains. In many places the actual fault lines can be seen in the steep
- cliffs. Although rivers flow through most of the rift valleys, there are
- few places where rivers have actually carved out their own valleys. In several
- places lakes have formed in the rift valleys; their depths run to as much as
- 600 meters, and they are surrounded by high mountains. There is no volcanic
- activity and little evidence in the soils of earlier volcanism. Yet, Sulawesi
- suffers from comparatively frequent earthquakes, originating below the sea.
- The local people are reluctant to build permanent homes and cultivate crops
- because of this and instead depend on the sea for their livelihood.
-
- One of Sulawesi's major problems is erosion, especially in the southern
- area. The climate is drier there than in the islands to the west, and the
- strong winds during the dry season have removed much of the topsoil. The
- hilly nature of the terrain encourages further erosion. Sulawesi has very
- little lowland, leaving few possibilities for agriculture. The rugged
- terrain has hindered communication and cut off existing lowlands from one
- another. Coastal shipping is more efficient and economical than roadbuilding,
- but at the same time it is difficult because of the extensive coral reefs
- lying off many parts of the coast. Ships must approach Ujung Pandang harbor in
- the south through carefully charted channels. Because of these difficulties,
- Sulawesi is isolated from the other islands.
-
- The main agricultural products of Sulawesi are copra and coffee grown on
- small estates. Rich fishing grounds lie offshore. The major mineral product is
- nickel, found in southeastern Sulawesi.
-
- The Lesser Sunda Islands
-
- The island of Bali and others in the Lesser Sunda Islands are
- mountainous. Bali is separated from Java by a shallow strait, less than 2.5
- kilometers wide. The essential feature of its landscape is a group of
- volcanoes that rise in the northeastern part of the island. Between these
- volcanic uplands and a limestone southern peninsula, there is a wide plain,
- which is the heart of Bali and where population density is the highest. The
- terrain is undulating, and the mountains rise gradually, in no way hindering
- communication and agriculture. This area is an example of what can be
- achieved by subsistence rice growers in hilly land, given the assets of
- fertile soil and adequate water.
-
- The other islands of the Lesser Sunda Islands, except Sumba and Timor,
- have no swamp problem and consist of fertile soil, amenable to agriculture.
- The drier regions of Lombok, Sumba, and Timor, the most infertile and
- inhospitable islands of Indonesia, suffer from a lack of water, and
- drought-induced famine is common. The government has started its development
- program in this region by establishing ranches for cattle and horses,
- keeping in view the production of beef cattle for domestic consumption and
- export.
-
- The Maluku Islands
-
- The Maluku Islands, historically called the Spice Islands, lie to the
- north of the Banda Sea between Sulawesi and New Guinea. Buru and Ceram lie
- in the central arc of these islands. For centuries Ambon, a comparatively
- tiny island near Ceram, has been the area's most important trading center,
- and in the early 1980s it was the most important harbor to the east of
- Sulawesi. It has an abundant rainfall, making the growth of timber
- possible, but it is not suited for other agriculture. Ambon, surrounded by
- coral reefs and atolls, and its marine gardens are renowned for their beauty.
-
- Halmahera is one of the less well-known islands. Unlike Ceram and Buru,
- it is an active volcanic area. The island's main staple crop is sago, a
- starchy producer of the sago palm that is used in foods and in textile
- stiffening. Eucalyptus trees are also grown for their oil and, along with
- spices and shrimp, are exported mainly to Japan. The inhabitants depend more
- on fishing than on agriculture for their livelihood.
-
- Western New Guinea
-
- About 47 percent of the island of New Guinea is Indonesian territory.
- Because it is located on a continental shelf, it has much in common with
- Sumatra, Java and Borneo. In the south and west, swamp-covered lowlands give
- way to shallow seas. The soil, however, has not received the benefit of
- volcanic activity during its formation. The island presents virtually all
- types of landforms, from lowland plains to high mountains with precipitous
- cliffs.
-
- The core mountains form an almost insurmountable obstacle to overland
- communication. Six permanently snow-covered peaks in the central range are
- the highest in Indonesia. The southern slope of the mountains forms a wall
- along the island, impeding communication between the northern and the
- southern part of the Indonesian portion of the island, but the coastal plains
- in the northern area are relatively narrow. Farther south, rivers form broad
- swamps that merge into shallow seas. Seasonal floods and siltation make the
- region's rivers of little value for communication; most can only be
- penetrated by small canoes. Not surprisingly, population density is low, and
- given the natural environment, the possibilities for agricultural development
- and increased habitation in the future are not encouraging. A copper-mining
- center around the Ertzberg ranges offers one positive incentive for
- immigration, but as yet most of the mine workers are temporary migrants sent
- from other parts of Indonesia. They live apart from the indigenous
- inhabitants and are unlikely to stay permanently.
-
- Climate
-
- Indonesia is generally classified as having a tropical climate.
- Variations and modifications are brought about by surface relief and by
- the position of the islands in relation to the seas that separate them.
- Precipitation, the most important element in the climate of the
- archipelago, shows great variation over the area as a whole. The equatorial
- position of the islands keeps sea-level temperatures, as well as humidity and
- air pressure, fairly constant from place to place and from month to month.
- Rainfall, by contrast, fluctuates both in total annual amount and in
- reliability throughout the archipelago. Altitude and position in relation
- to prevailing winds are two of the factors that determine its distribution.
- Virtually all of the islands receive some amount of rainfall. In parts of
- Sumatra, Borneo, and western New Guinea, precipitation exceeds 300
- centimeters a year, causing extensive leaching of the soil and the development
- of large swamps. Yet in some parts of the Lesser Sunda Islands, an
- insufficient total annual rainfall, together with a prolonged dry season, is a
- great handicap for agriculture.
-
- Most of the rainfall is associated with the two monsoons that blow at
- alternate times of the year. Some precipitation is also obtained from the
- lighter, local winds that blow in the months between the monsoons. The two
- monsoon winds, generally referred to as the East and West monsoons, blow in
- toward the equator from a southern and a northern direction, respectively.
- Indonesia's geographical position as an archipelago between two large
- continental areas is important in the building of the wind pattern of the
- area. In July and August, high pressure over the desert of Australia causes
- winds to move from that country toward the northwest. As the winds reach the
- equator, the rotation of the earth causes them to be deflected, and they
- turn in a northeastward direction toward the southeastern Asian mainland.
- During January and February a corresponding high pressure system over the
- Asian mainland causes the pattern to be reversed. The resultant monsoon is
- strengthened by additional windflows from the Indian Ocean. The reinforcement
- makes this West Monsoon more significant in the yearly climatic pattern than
- the weaker East Monsoon, which carries less moisture. The West Monsoon is the
- most important season for agriculture. Yet, local topographical conditions
- greatly modify the general wind pattern.
-
- Areas in the archipelago can be distinguished on the basis of mean annual
- precipitation. Rainfall is heaviest (exceeding 295 centimeters) in the western
- coast and uplands of Sumatra, central portions of Borneo and Sulawesi, the
- mountains of western New Guinea, and a few isolated districts in Java, Bali,
- Lombok, and Sumbawa, where high peaks advantageously placed in relation to
- the prevailing winds encourage heavy precipitation. In comparison with the
- rain forest, most other portions of Sumatra, Borneo, Sulawesi, and western New
- Guinea, as well as western and central Java, receive moderate rainfall and are
- thus better suited to agriculture. The third area, having rainfall less than
- 195 centimeters, includes small parts of northeastern Sumatra, north of
- Langsa; most of eastern Java; all of Madura; the greater part of the Lesser
- Sunda Islands; a small part of southern New Guinea, and-southward from
- there-the Aru and Tanimbar islands in the Arafura Sea. In this area there is
- a lengthy dry season and an increase in unreliability in both total amount
- and monthly distribution of rain. The last area, which has rainfall as low as
- 87.5 centimeters or less, covers 0.6 percent of the national territory,
- mostly in the Lesser Sunda Islands, the eastern tip of Java, and two parts
- of Sulawesi. Here the main problem is the extremely irregular distribution
- of rainfall, which prevents farmers from ever being sure when to plant
- their crops.
-
- Unlike precipitation, temperature throughout the Indonesian archipelago
- is relatively constant over the year. Seasonal change is negligible because of
- the equatorial position of the country and the modifying influence of the
- surrounding seas. Altitude is the most significant factor in temperature
- modification. Changes in temperature as a result of varied altitude often
- give rise to frosts at night, particularly where there are sheltered
- depressions rather than open mountainside.
-
- In all parts of the archipelago, fluctuations in precipitation rather
- than any noticeable change in temperature define the seasons. Fog is fairly
- common in areas above 900 meters. Another important climatic element in
- tropical areas of Indonesia is evaporation. The rate at which moisture is lost
- into the atmosphere influences plant growth as well as soil formation and
- erosion. Where leafy forest covers the ground, as in the interior rain forest
- of Borneo, much of the rain never reaches the soil. This circumstance,
- coupled with ill-planned deforestation, has caused much of the once
- forest-covered area to be bare and infertile.
-
- There is very little change in the length of daylight hours. The
- difference between the longest day and the shortest day of the year is only
- 48 minutes. Because of the great distance from one end to the other, the
- country is officially divided into three time zones, corresponding with the
- three major geologic subregions of the country. The first one, the Sunda Shelf
- region, is in the west at Greenwich mean time (GMT) plus seven hours; the
- second, in the region of deep seas and geological instability, is at GMT plus
- eight hours; and the third, the Sahul Shelf region in the east, is at GMT plus
- nine hours.
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