A Supplemental HCVF Assessment on the Sumatran Tiger ...

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FINAL REPORT Tiger <strong>HCVF</strong> <strong>Supplemental</strong> <strong>Assessment</strong> – Serapung FMU purposes of population viability assessment, oil-palm estates are also assumed not to represent tiger habitat. Many historical and recent reports from local people indicate tigers are present in and around the FMU and widespread across the Siak-Pelalawan forest block which, along with the Kerumutan forest block to the south, represents the area identified as Tiger Conservation Unit (TCU) 150. GIS analysis based on currently-known concession holdings indicates that by 2007 TCU 150 will be separated into two isolated and much reduced constituent blocks. This optimistic approach, ignoring applications for additional concessions at the provincial and district level, estimates that a maximum of 305,000 ha of natural forest will remain within the Siak-Pelalawan block by 2007. However, given recent conversion trends witnessed across Riau and throughout Sumatra (see: FWI/GFW 2002) a realistic prediction for future habitat availability in the Siak-Pelalawan block is that only the currently protected areas of forest (approximately 40,000 ha) will remain in the medium-term. Some additional natural forest will be provided by mandatory set-aside areas within forest concessions, although these are considered to provide a very limited contribution to maintenance of the tiger population due to their characteristic lack of connectivity and small size. With respect to the landscape context of the FMU, currently available information relating to other concession applications suggests that adjacent forest areas to the north and west of the FMU will, in the near-term, be clear-felled and developed as plantations. This will lead to a total loss of connectivity between the FMU and the wider Siak-Pelalawan forest block unless (1) extensive habitat corridors are maintained by the neighbouring estate or (2) the area in the vicinity of Tasik Pinang Lake is gazetted as a protected area. This loss of connectivity would mean that, even despite vigilant management and effective protection by the FMU, tigers will not persist in the moratorium area in the medium to long-term. By extrapolation of tiger densities (1-4 tigers/100 km 2 ) obtained from other studies in Sumatra, the maximum expected forest habitat expected to remain in the Siak- Pelalawan block by 2007 would be sufficient to sustain a population of between 30 and 120 adult individuals. Photo-capture frequencies recorded during this study suggest that the upper range of previously recorded Sumatran tiger density is more likely to be an appropriate estimator for forests adjacent to the Serapung FMU. However, over the wider Siak-Pelalawan landscape a conservative estimator of density is suggested to be between 2 and 3 individuals per 100 km 2 . Such densities provide a cautious estimate for the tiger population in the Siak-Pelalawan landscape of between 60 and 90 individuals. A single contiguous population of 60-90 tigers, in comparison to the current global population estimate of 500 Sumatran tiger individuals, represents a significant contribution to the survival of the subspecies (12-18% of total numbers) and promotes Siak-Pelalawan as a key landscape component of the Indonesian Sumatran Tiger Conservation Strategy. If however only approximately 40,000 ha of fragmented and isolated tiger habitat were to remain, as is likely in the medium-term given no immediate conservation intervention, then the tiger is predicted to rapidly become extinct in the Siak-Pelalawan region. The TCU Framework and the PHVA process are in agreement that the greater the tiger carrying capacity of habitat the greater the probability of persistence of the tiger population. Previous PHVA analyses have shown that a contiguous habitat block with a carrying capacity of 100 tigers will be viable over the long-term given limited negative influence from external factors such as poaching. Therefore to maintain the independent and long-term viability (>100 individuals) of the existing tiger population in the Siak-Pelalawan forest block a minimum of 250,000 ha of contiguous forest habitat Sumatran Tiger Conservation Program Pg 48/68
FINAL REPORT Tiger <strong>HCVF</strong> <strong>Supplemental</strong> <strong>Assessment</strong> – Serapung FMU is recommended provided that densities can be maintained at 4 tigers/100 km 2 . A population of 50 individuals, offering a minimum acceptable level of viability given that effective management and intensive protection can be implemented, would require at least 125,000 ha of habitat to be maintained area. Not all of this area would have to be strictly protected forest but components of it could represent contributions from production forest areas managed under sustainable forestry schemes where clearfelling is prohibited. The controlled disturbance caused by logging in such areas will enhance the habitat for tigers through encouraging secondary growth and an associated increase in density of the primary tiger prey species (Heydon 1994, Johns 1997). The strictly protected core areas would serve as a refuge for tigers during periods of active logging in the adjacent production forest buffer zones. In addition to this, planning and spatial organisation of regulatory “set-aside” areas within adjacent HTI/oil-palm estates should be carried out in a manner that enhances and protects this conservation area (e.g. from fires, from disruption to hydrology, etc.) acting as, or supplementing, habitat corridors between essential landscape components. The adjacent plantations and estates themselves can, through proper design, provide a further positive contribution by serving as a barrier against intrusion by illegal loggers into the conservation area. It should be noted, however, that a poorly managed estate will actually facilitate illegal logging if its road, rail and canal systems are inadequately guarded. However, given that this aspect can be managed effectively, coastal areas would (all other factors being equal) be of more utility as a developed and managed “buffer” between settlers and core areas, than they would as components of the protected forest. The cost-benefits of attempting to conserve these coastal zones, due to the proximity of settlers and ease of access for illegal loggers, will always be greater than for core areas further inland. An immediate priority for the Siak-Pelalawan block is the implementation of intensive ground surveys and associated landscape analysis in order to establish (1) tiger status, distribution and density, (2) habitat availability and condition, (3) intrinsic threats to the habitat and its tiger population and (4) future land-use planning and conversion trends. The overall objective of these surveys should be the identification of core and peripheral areas for inclusion within a landscape-level tiger conservation area, through provision of base-line data, identification of landscape constraints and socio-political limitations, and through assessment of general levels of stakeholder support. Ideally no further licences for clearance of forest in the Siak-Pelalawan block should be granted until a landscape conservation strategy and protected area network has been developed and implemented. 5.4 Tiger-Human Conflict Tiger-human conflict is not only important from a human perspective, with injury and death of both people and their livestock - leading to significant material loss, but the resulting death of the “problem” tiger through retribution is a major contributor to the tiger’s overall decline (McDougal 1987, Nowell & Jackson 1996, Tilson & Nyhus 1998, Tilson et al. 2001, Nyhus & Tilson 2004). The specific causal factors behind recent tiger-human conflict in and around the FMU, resulting in 11 conflict events during the last 5 years, could not be ascertained during this study. Forest clearance and/or intensive disturbance by logging are the most likely causes when we consider the evidence from human-tiger conflict observed in other areas of Sumatra. However, this and previous studies have been plagued by the difficulties of identifying direct causal relationship, due to the acts of forest clearance and logging being confounded by the increased probability of encounters between tigers and humans due to high density of people in the forest. Nyhus & Tilson (2004) have described in detail similar findings in intermediate disturbance areas such as Sumatran Tiger Conservation Program Pg 49/68
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A Supplemental HCVF Assessment on the Sumatran Tiger ...

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