Ecoregional Assessment of Biological Diversity in East Kalimantan

East Kalimantan Ecoregional Assessment: Chapter 2 – Target Ecological Systems
These include the Dulit Frogmouth, Batrachostomus harterti; Hose’s Broadbill,
Calyptomena hosei and Pygmy Darkeye, Oculocincta squamifrons (Sujatnika et al. 1995).
Mammal species are also usually moderately high in Lower Montane/ Cloud Forest in Lore
Lindu National Park, and do not decline substantially from their diversity in lowland forests,
except for bats, which decline dramatically above 1500m a.s.l. Evidence from Peninsular
Malaysia suggests that biomass of primates (Caldecott 1980) and some groups of soil
macrofauna (Collins et al. in MacKinnon et al. 1996) may often be highest in these lower
montane rainforests, especially oligochaetes. This does not appear to be the case with the
higher order primate Orangutan, which tend to favor vegetation below 1000m a.s.l. Nijman
& Meijaard in Nijman (2001) stated that in East Kalimantan, the Bornean Gibbon was
“confined to closed canopy forest in the lowlands and hills up to c.1500m a.s.l.” Suzuki et al.
(1997) noted that in the Berau and Kutai District of East Kalimantan, Bornean gibbon is
more common on hills and uplands.
MacKinnon et al. (1996: Table 7.4) reported that there was no clear trend for gibbon to
decline in density between altitudes of 0-900m. Numbers of groups of gibbon in Sabah (H.
muelleri) also did not decline up to 1500m above sea level – although they did in the
altitudinal range of 1500 – 3000m. However, it is possible that this decline at very high
altitudes was strongly influenced by their typical low density in cloud forests. This would be
expected given the low, stunted nature of the trees and the low abundance of fruit in cloud
forests. It is reasonable to assume that gibbon group size would also decline markedly in
upper montane rainforests (1800-2000m).
Evidence from Mt. Kinabalu, in the Malaysian State of Sabah, indicates that species richness
of butterflies in these Lower Montane Rainforests is less than in Lowland Rainforests, but is
higher than in the Upper Montane Rainforest /Cloud Forest system type.
Conservation issues and threats
• Logging
Logging of Lower Montane Rainforest is much less than what occurs below 1000m a.s.l.
because of the costs of operating on high slopes. However, there is some logging above
1000m. The contribution of such logging to increased suspended sediments in streams
and rivers caused by erosion on these steep slopes is out of proportion to the relatively
small areas that are logged. Also, the removal of forest from the lowland areas
surrounding these Montane forests will be critically dependent upon the seed production
from these protected forests to replenish and restore the lowland forests – provided of
course that they are left alone for decades to naturally revegetate. This seems unlikely
given current population and industrial development trends in the region.
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