Ecoregional Assessment of Biological Diversity in East Kalimantan

East Kalimantan Ecoregional Assessment: Chapter 2 – Target Ecological Systems
hydrological connection; they were probably physically connected in the recent past; and
they are vulnerable to similar environmental threats.
Portfolio Design
The goal for East Kalimantan is 60% of all Peat Swamp Forests. The portfolio achieved
65.6% (2% of total in Stratigraphic Unit 1, 7.25% in Unit 2, 44.7% in Unit 3, and 10.4% in
Unit 4). These were distributed to represent their actual proportions in each stratigraphic unit
and in each annual precipitation zone, if possible.
Results
The distribution of Peat Swamp Forest varied greatly in each stratigraphic unit, with 65% of
the areal extent in the Province found in SU-3. Sixty percent (60%) of these swamps also fell
within the intermediate precipitation zone (2000 - 3000 mm). The portfolio should then
represent the distributional inequity of this ecological system type in both Stratigraphic Units
and precipitation zones. There was also a significant difference in the viability indices for the
occurrences. Those in Units 1 and 2 are in better condition than those in Units 3 and 4.
Swamp Forests were most damaged in SU-4 and those in SU-3 of low viability were
included in the portfolio because they are considered important for the ecological function of
the Kinjau River and the middle Mahakam Lake area. Peat Swamps around the mouth of the
Sesayap, Berau and Wain Rivers are also incorporated into the portfolio because they form a
broad ecosystem alliance with Mangrove Forests and are ecologically important to the
function of these rivers near their deltas, despite their individually poor viability ranking. The
latter had a generally higher viability index than those in SU-3. Interestingly, there is no Peat
Swamp Forest in the immense delta area of the Mahakam River, apparently neither extant
nor historic.
The reasons for the low viability index for the middle Mahakam area occurrences are
discussed in the previous Description and Threats sections. However, large tracts of Peat
Swamp Forest associated with the Kinjau River are included because of the importance of the
‘black rivers’ flowing from these forests to native fish and other fluvifauna in this area – as
well as their importance to terrestrial fauna and flora, particularly primates. This is also based
upon expert opinion that, if further protected from fire and other human disturbance,
occurrences selected in the portfolio could rehabilitate naturally. This is an important point,
because the matrix lowland rainforests in the middle Mahakam area around these Peat
Swamp Forests also have ‘poor’ or ‘very poor’ viability indices. They have been converted
for agricultural purposes or have been burned on multiple occasions and would take a very
long time (>200 years) to recover their natural floristics and structure – if at all. The key to
this possibility is the absolute protection of the forests from further disturbances – which in
this day and age is neither practical nor realistic in this particular area.
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