Truly Untouched Rainforest
The Sungai Imbak Virgin Forest Reserve
is a Class VI Virgin Jungle Reserve of an area of approximately
18113 hectares, located in central Sabah and divided into six
blocks. Some 35 km away is the better known Maliau Basin. Access to
the reserve is difficult and only possible by 4x4 over gravelled and
dirt roads, and since there is no infrastructure whatsoever the area
remains largely pristine.
The Sungai Imbak Virgin Jungle Reserve was initially part of the
Sungai Pinangah Forest Reserve, which was gazetted in 1965. In 1984
the reserve was split into two reserves, one being the Sungai
Pinangah Forest Reserve (Class
II) and the other being Sungai Imbak Virgin Jungle
VI). Both reserves are managed by Yayasan Sabah, though
due to its rugged terrain there is no management plan (logging plan
or other use) for Sungai Imbak, very fortunately.
The region is mountainous with two main ridges forming two arcs. The
highest peak is at 1551 m a.s.l. at the south-eastern-most part of
the reserves. The ridge spurs run into the valley where the Imbak
River flows. Travelling by foot is best when along spurs rather than
traversing. Many hillsides have slopes greater than 25°. The Imbak
River which flows into the Kinabatangan River, making the Imbak an
important water catchment for the Kinabatangan.
The forest of the Imbak Reserve is pristine in the sense that it has
not been logged or affected by any major forms of natural or human
disturbance. The Dipterocarpacea is the most dominant tree family in
the four general forest types that are recognized in the Imbak area:
1) lowland mix dipterocarp forest, 2) upland mix dipterocarp forest,
3) lower montane kerangas forest, and 4) upper montane kerangas
The dipterocarpaceae, or dipterocarps
are one of the main features of Sabah’s forests. Most of them
highly valuable hardwoods, the trees are tall (70 meters), with
a very long, straight trunk that only branches out at some 50
meters height and forms a close ‘cauliflower’ canopy. In a
10-day survey of the area 58 dipterocarp species from 8 genera
were recorded. This accounts for 29 % of the 200 species of
dipterocarp known to occur in Sabah. Of these 58 species, 30 are
endemic to Borneo, i.e. they occur naturally only on the island
of Borneo. For comparison, 48 species have been recorded from
the Maliau Basin Conservation Area and 35 from the Kabili-Sepilok
Forest Reserve. Dryobalanops beccarii (kapur merah) and
Shorea laevis (selangan batu kumus) stand out as being
particularly common in the main forest canopy of the mix
dipterocarp forest of the Imbak. Large kapur merah trees are
often hollow and therefore provide important nesting sites for
birds such as hornbills. S. laevis is one of the most
important sources of Selangan Batu timber, known for its
strength and durability.
Surveys and botanical collection trips
were conducted in August of 1992, during a period of mast fruiting.
This was done by the Sabah Forestry Department, in collaboration
with Yayasan Sabah. However, the collecting activities did not
venture into the valley proper and the two main ranges of Sg. Imbak.
Prior to this expedition, there were no known botanical explorations
of the Imbak area. All collections (150 in total) made during the
1992 botanical expedition are kept for permanent record at the
Sandakan Herbarium in Sepilok.
An major expedition was organised by the Sabah Forestry Department
in July 2000 and further faunal surveys were carried out during an
expedition in 2000 by the Sabah Wildlife Department and the Sabah
State Museum. However, information on this survey is not yet
Anywhere in Sabah, lowland mixed
dipterocarp forests (MFD) represent an extremely important
reservoir of biodiversity. At the same time it is the principal
source of commercial timbers. For this reason most of the
lowland MDF have been heavily exploited, while a large portion
have been lost to agricultural development. At present, the
Imbak supports one of the few relatively large tracts of
pristine dipterocarp forests remaining in Sabah, underscoring
its immense value for biodiversity conservation.
A major constraint to large scale reforestation efforts in Sabah
is the availability of reliable sources and sufficient amounts
of planting material. With the ever increasing efforts at
reforestation, the Imbak is seen as an important natural source
of planting material (or seed production area).
Despite those two botanical surveys, much of the Imbak remains
unexplored and a lot remains to be studied about the flora of
the Imbak. For instance, the highest area of the Imbak (just
over 1,500 m a.s.l.) located at the south-eastern corner has yet
to be visited botanically. Although the sample plots that were
established are not sufficient to provide a comprehensive
account of the vegetation, they provide a good indication of the
main floristic associations of the Imbak. Such information can
be built upon over time as time and resources become available.
Considering the current state of forest conservation in Sabah,
the protection of the Imbak merits serious consideration.
New species and a new record for
Two new tree species have been described
from the Imbak. Dipterocarpus megacarpus was described by
Madani (1992) following the first expedition to the Imbak. The
second species to be described was Ceriscoides imbakensis (Azmi,
2000), a very rare tree from the Rubiaceae family. The only
two collections of this species are from the banks of the Imbak
River. Ruth Kiew, a begonia specialist from the Singapore Botanic
Gardens, collected two Begonia species during the 2000 Imbak
expedition. These collections have yet to be described and named.
Had there been a greater participation from plant specialists on the
two expeditions, more new discoveries would have been likely.
How to Get to the Sungai Imbak Forest Reserve & Accommodation
Nearly impossible - plus access is restricted, and probably rightly
so if the pristine nature of this part of Sabah is to be totally
protected. No accommodation is available, and no other
infrastructure has been erected, or is planned.
photos to be added soon