Ecology of Sulawesi. Tony Whitten
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so just east of Gorontalo6 (Lowder and Dow 1978), and possibly in the Latimojong Mountains of the southwest peninsula. An analysis of leaves from herbs collected on Salayar Island, south of the southwest peninsula, revealed high concentrations of copper (80-600 mg/g compared with normal concentrations of <50 mg/g), indicating that rich deposits might also be present there7 (Brooks et al. 1978).
Gold. Gold is generally associated with copper deposits, and the exploration for copper in North Sulawesi has revealed locations of potential large, commercial gold mines. Four mines that were worked early this century have been exhausted for commercial exploitation. New exploration licenses, however, have recently been issued.
Figure 1.7. Distribution of asphalt-impregnated limestone on Butung Island.
After Anon. 1985a
Nickel. Nickel ores are derived from the weathering of ultrabasic rocks and are also found in the molasse deposits derived from these rocks. The ore deposits around Soroako and Lake Matano are mined by P.T. Inco and those around Pomala'a, south of Kolaka, are mined by P.T. Aneka Tambang.
Minor Products. Deposits of sulphur are known only from Soputan and Mahawu volcanoes in Minahasa and these have been exploited since the 1920s, although production is currently not very active. Kaolin or white clay is produced on a small scale in North Sulawesi for the ceramics industry. Salt is produced in coastal salt pans by small-scale operators in South Sulawesi. Quartz sands and silica were mined in South Sulawesi up to 1977 since when it has not been economically viable to do so.
SOILS
The description of soil types is hampered because there is no system of soil classification that has gained universal acceptance in terms of definitions or names. From experience and observation it has been said that "scientists who are otherwise reasonable and unemotional are liable to behave quite differently when discussing this topic" (Mulcahy and Humphries 1967). In many cases, hybrid systems have evolved using names from various systems with the result that those with little knowledge can become extremely confused. For the purposes of this section the FAO system is used because it has wide recognition and because the names are easily pronounceable.
The major soil types on Sulawesi and their approximate distributions are shown below (table 1.3; fig. 1.8).
* Horizons are layers of soil roughly parallel to the surface which have fairly distinctive characteristics.
After Young 1976
Figure 1.8. Approximate distribution of major soil types on Sulawesi.
After Anon. 1976
CLIMATE
Palaeo climate
The palaeoclimate of Sulawesi does not appear to have been studied specifically, but analyses and summaries of palaeoclimate in Southeast Asia are available (Verstappen 1980; Flenley 1980; Whitmore 1981; Walker 1982; Morley and Flenley in press).
The climates of Sulawesi and the rest of Indonesia today, are quite unlike the climates which dominated the region during most of the Quaternary and before. As was shown on page 2, the world's landmasses have moved around, joining and separating, and this has led to changes in climatic regimes. Tropical and subtropical conditions, and the animals and plants associated with them, extended further away from the equator during the Tertiary than they do now and this has influenced the present distribution of animals and plants (p. 63).
During the latter part of the Quaternary, temperatures in the temperate areas of the world repeatedly rose and fell above and below present temperatures. In the cooler periods the ice sheets of the Arctic and Antarctic extended and this took great quantities of water out of the hydrological cycle (fig. 1.9). This in turn caused sea-levels around the world to fall. The maximum fall in Southeast Asia was about 150 m below present levels. This exposed large areas of dry land beyond the present coastlines-indeed, it uncovered three times the present area of the Sunda Shelf and twice the present area of the Sahul Shelf.8 When the sea-level was only 40 m below present levels it would have been possible to walk in a straight line between Banjarmasin and Surabaya, Saigon and Kuching, Singapore and Pontianak, and Merauke and Darwin. The effective area of Sulawesi was also increased but to a much lesser extent (fig. 1.10). Examination of bathymetric contours reveals features that may have been river valleys when the sea-level was lower (fig. 1.11).
Ocean currents which now enter the Indonesian Archipelago through the Torres Straits, the South China Sea, the narrow straits between many of the Lesser Sunda Islands and the straits between Mindanao and the Sangihe/Talaud Islands would have been blocked and their buffering effect on climate would have been lost. The Sulawesi Sea (between the Philippines and Sulawesi) and the Makassar Straits would have been much more enclosed but the currents entering the Molucca Sea (between Halmahera and Sulawesi) towards and from eastern Sulawesi would have been only marginally obstructed. The main Sunda and Sahul landmasses would have experienced a more continental climate (greater diurnal temperature range, lower rainfall and humidity) but this would have been rather less pronounced on Sulawesi. The lowering of sea and land temperatures during these cool periods would also have reduced rainfall and humidity. It has been estimated that the rainfall 11,000 years ago was 30% of present values in the equatorial zone.
Figure 1.9. Hydrological cycles (a) in warm conditions and (b) in cool conditions. Note the fall in sea-level because water in the form of ice is unable to flow to the sea.
Figure 1.10. The area of Sulawesi and neighbouring land-masses exposed when the sea-level was 100 m below present levels.
After van Balgooy in press
The cooling of the whole earth during the glacial periods lowered the lowest altitudes at which ice remained all year and snow fell, and lowered the upper altitude at which montane trees grew. The maximum temperature depression during the Quaternary occurred 18,000 years ago when, in New Guinea, temperatures at 2,500 m were 10°C lower, but at sea-level only 2° or 3°C lower, than at present. The tree line (the altitude at which trees are no longer able to grow) was lowered about 1,500 m in New Guinea but only about 350-500 m in Sumatra. The sea-level changes also had considerable impact on corals (p. 215).
The zone where the curtains of rising air of the northern and southern hemisphere meet is called the Intertropical Convergence Zone (ITCZ), and in the cool, dry glacial periods this was probably south of its present position (that is roughly over the equator). It is a zone of frequent, showery rain, to the north of which is a high pressure belt with relatively low rainfall. Thus, when the ITCZ lay south of the equator, parts of northern Indonesia (including Sulawesi) would have experienced drier, more seasonal climate with lower rainfall and humidity and greater seasonal change in mean daily temperature (Verstappen 1980).
Figure 1.11. Bathymetric map of the Sangkarang Archipelago to show the deep channels that are probably drowned riverbeds.
Temperatures during the warmest parts of the Quaternary were only 1° or 2°C higher than now (at sea-level) and at this time the water released from the polar ice caps caused sea-levels to rise. There is no unequivocal evidence that shorelines have been more than 6 m higher than at present during the warm periods of the Holocene, but sea-levels could have reached up to 25 m above present levels during the Pleistocene. The most recent sea-level maxima detected off the southwest peninsula were 4,500 and 1,600 years ago when sea-level was 5 m and 2.5 m higher respectively (fig. 1.12) (de Klerk 1983). This agrees closely with evidence from elsewhere in Southeast Asia (Tjia 1980; Tjia et al. 1984). Whereas this rise had a marked