Vegetation Survey and Habitat Assessment of the Tesso Nilo Forest Complex

The current rate of land conversion suggests that virtually all remaining lowland forests in Sumatra will disappear by the year 2004. WWF's Asian Rhino and Elephant Action Strategy (AREAS) project is currently exploring ways of achieving an equitable balance between conservation and exploitation. AREAS is developing a conservation landscape for the Sumatran Elephant that will result in protecting the192,000 ha Tesso Nilo Forest Complex in the province of Riau as a core area. The forest complex is central to global conservation issues as it constitutes one of the last remaining patches of lowland Sumatran forest. In order to provide necessary baseline data, a rapid appraisal of the Tesso Nilo (TN) reserve was conducted by WWF staff supported by the Center for Biodiversity Management (CBM) between the 28 October and 10 November 2001.

Existing information and data were used in conjunction with recent remotely sensed imagery to locate representative sites and to assist with subsequent habitat assessment and extrapolation for mapping and conservation planning. The high rate of current and ongoing rapid forest conversion by pulp mills, oil palm plantations and illegal logging added an urgency that meant that only a limited number of ‘intensive’ 40 x 5m plots could be used to record all vascular plant species, plant functional types (PFTs), vegetation structure and site physical variables. These were complemented by a greater number of plots in which vegetation structure and site physical variables alone were recorded. Statistical analyses in other areas of Sumatra confirmed certain vegetation structural attributes were highly correlated with species and PFT richness. This meant the ‘structure’ plots were potentially useful as indicators of biodiversity and as a basis for extrapolating habitat via remotely sensed imagery. To support this contention as well as to compare TN forests with other areas of lowland Sumatra, the TN data were analysed together with data from a previous multi-taxa survey in lowland Jambi Province of Central Sumatra. Despite considerable logistical problems due to poor access, 24 ‘structural’ and 9 ‘intensive’ sites (including an Acacia and a rubber plantation site) were recorded using a standard field method.

The highest prior record of 114 species in Jambi, was exceeded by an extraordinary 218 species in one TN plot (more than 10% of the number of native plant species of the UK). In that plot 26 plant families, 48 genera and 66 species occurred in the first 5 x 5m quadrat of the 40 x 5m transect There are no published records available that indicate similar levels of plant species richness anywhere else in the world’s lowland forests. A comparison of 7 TN forest sites with an equal number from Jambi revealed a total of 326 genera, with 159 genera shared and 244 and 243 from TN and Jambi respectively. Confirmation of identification at species level is ongoing at the time of writing but numbers are unlikely to change significantly.

In TN forest plots, plant diversity corresponded generally with that of birds and mammals. The extraordinary richness of lowland Sumatran forests is, ironically, matched by the speed with which land conversion is taking place. The present report provides new and critical data and information that will support a strong national and international case for immediate conservation of one of the world’s most valuable remaining biodiversity resources.

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