The occurrence of Imperata cylindrica in Borneo

There is little precise cartographic information about the extent of lalang in Sarawak, but it is not believed to be a major problem. Shim (1993: 23) attributes the absence of large tracts of sheet lalang to the lack of a pronounced dry season: "nearly year-round rains do not allow lalang to reach a fire climax, and it nearly always loses in competition with other weeds." Freeman, in his well-known Iban Agriculture (1955), documented cases where too-frequent cropping by shifting cultivators had led to lalang infestation, which was apparently common in the Kapit district. Padoch (1982b) has questioned the universality of this behaviour among Iban pioneers. As noted in chapter 6, the phase of pioneering shifting cultivation by Iban groups is now over. The only figures available for the extent of grassland 72,000 ha - date from 1974 and include scrub (Hatch, 1982). Shim (1993) believes the actual area of grass to be much smaller.

In Sabah the figures are also old, giving an area of 155,000 ha in 1970; more than half of this was in the West Coast Residency around Kudat and Kota Belud (Shim, 1993). An examination of recent topographical maps in Sabah revealed much apparently successful reforestation with Acacia mangium in this region. Reforestation is also being tried in another famous lalang area, the Sook Plain, in the Interior Residency (see chap. 8). The formation of this grassland has been well documented as taking place after a fire in 1914, in which all the existing swamp forest was burnt and did not regenerate, the exposed white sand soil being colonized by a mixture of lalang and bracken (Matthews, 1917; Cockburn, 1974; Shim, 1993).¹

In contrast to the quite moderate expanses in Malaysian Borneo, the four Indonesian provinces of Kalimantan have been estimated to contain 1.4 million ha of grassland, out of 10.3 million ha in the entire country (Tjitrosoedirdjo, 1993). These figures are drawn from the maps compiled by the Regional Physical Planning Programme for Transmigration (RePPProT) and represent the situation around 1982. Although not all this grass is Imperata, especially in eastern Indonesia, in Kalimantan the grasslands are dominated by that species. South and West Kalimantan are the two provinces in which the human impress upon the land has been most marked. They contain the highest population densities and, perhaps coincidentally, the largest expanses of Imperata cylindrica, although these usually occur in rolling or hilly areas marginal to the main population centres. Alang-alang is estimated by the RePPProT study (1987b) to cover about 17 per cent of the small province of South Kalimantan - about 623,000 ha. This constitutes a grassland area almost twice that of West Kalimantan (340,000 ha), which makes up only 2 per cent of that province (RePPProT, 1987a).

The western foothills of the Meratus mountains (including the Riam Kiwa) and the middle Melawi basin (including the Ela Hulu) stand out prominently for their vast fields of alang-alang (fig. 9.1). In South Kalimantan the grasslands extend almost unbroken in a swathe of more than 300 km from north to south. Many of these areas occur in a low-rainfall belt in the lee of the Meratus mountains, but climate is not a sufficient explanation because the grass also exists in higherrainfall areas. It becomes prominent again east of the mountains, and occurs in patches up the east coast into East Kalimantan, for example near Samarinda. In West Kalimantan the patches tend to be more scattered, but notable areas include an extensive and compact block in the middle Melawi (about 150,000 ha) and a dense mosaic of grassland interspersed with swamp forest at Kendawangan in the far south. In Central Kalimantan there are also important stretches of sheet alang-alang in the south near Pangkalan Bun.

Lest the occurrence of such grassland becomes exaggerated, there are many areas throughout Kalimantan where the map sheets (at a scale of 1:250,000) indicate either no Imperata or very small areas only. Most of the mountainous interior and the swampy coast are unaffected. The Land Resources of Indonesia: A National Overview (RePPProT, 1990) does not separate grassland from scrub and shifting cultivation in its vegetation map, thus creating the impression that it is all the same, which is far from being the case. Although the south-east stands out as by far the most prominent grassland district in Kalimantan, it proved impossible to map the alang-alang at a scale small enough to represent the four provinces on one page; in most areas the patches would be too tiny to be visible.

Fig. 9.1 Two grassland areas of Kalimantan (Source: RePPProT, 1987a, 1987b. Map series 1: 250,000, Land Use and Current Forest Status)

On the ground their visibility is not in doubt. The occurrence of such large expanses of sheet alang-alang leads to the question of when and how these landscapes were created. Human activity has certainly been the trigger, but what kind of activity, in what particular cultural or economic circumstances, and over what period? What has been the relevance of particular site features such as climate or soils? Has population pressure, or lack of it, been part of the explanation? Simplistic explanations such as "improper shifting-cultivation practices" will obviously not suffice. Shifting cultivation, in particular circumstances, might be one causal factor among several, but is unlikely on its own to have created the really large expanses of grass. In-depth probing of both contemporary informants and historical sources is necessary to try to tease out the picture. Studies of current usage of the grasslands and the long-term sustainability of present livelihood systems form the other essential component to any study of "criticality."2