Ecoregional Assessment of Biological Diversity in East Kalimantan

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East Kalimantan Ecoregional Assessment: Chapter 1 – Background & Analysis Process • Although in some U.S. situations, patchy (mosaic) communities may be more ecologically variable than matrix communities (TNC 2000), the reverse seems to be true in some forest types in East Kalimantan. For example, Lowland Rainforests exist on all 10 RePPProT land system types and tend to reflect the intensely complex Pleistocene drying pattern on lowland edaphic types. Variation in faunal and floral composition beneath the canopy is surely more subtly expressed than can be distinguished through aerial photography or satellite imagery. • For widespread target systems (Lowland Rainforest, Lower Montane Forest, Mangroves and Major Rivers), it was decided that one element occurrence per stratigraphic unit within each precipitation zone (if possible) would be a minimum selection goal, coupled with a percentage goal for its overall areal extent. • The number of target ecological system occurrences selected will also depend on the number required to ensure functionality of the Major River selected within each Stratigraphic Unit; this includes a functional buffer or riparian “belt”(500m – 2km) along the length of the river corridor and adequate areas of upper catchment area (hulu) and delta habitat at the terminus. Goals were applied for each Stratigraphic Unit – resulting in separate preliminary portfolios for each. It was acknowledged that this approach would result in overrepresentation of some system types, but this also insured that the best representatives for each system type were being advanced for consideration in the ultimate portfolio of sites. Therefore, no high quality site would be overlooked because a particular system type had already met a priori goals elsewhere in the East Kalimantan planning area. When all stratigraphic units were “rolled-up” to review progress towards overall conservation goals in the portfolio assembly, some less viable (i.e. lower ranking) areas were dropped when they resulted in over-representation of a particular system type. They were not eliminated, however, if they comprised the only representation of that particular ecological system type within the stratigraphic unit or within one of the three precipitation zones. Minimum portfolio assembly goals for target ecological system occurrences were based on the percentage of area of each stratigraphic unit and each precipitation zone occupied by the target system type (Table 1.1). Table 1.1 - Portfolio Goals: Target System Distribution Patch Size GOAL Upper Montane/ Cloud forest limited small to moderate 100%* Lowland Limestone Forest limited small to large 70% Freshwater Swamp Forest limited single, small 70% Peat Swamp Forest widespread moderate 60%** Heath Forest widespread small 60%** Mangrove Forest widespread moderate 50%** Lower Montane/Montane Rainforest widespread large 30% Lowland Rainforest widespread matrix 20% Major River widespread linear 4*** * Although Upper Montane/Cloud Forests in East Kalimantan are limited and are small to moderate in size, 100% of them are selected as a goal. They are extremely fragile habitats that retain a high percentage of endemic flora and fauna. Further, there 21
East Kalimantan Ecoregional Assessment: Chapter 1 – Background & Analysis Process appears to be no competing land use proposed for them at this time. Also, a very large percentage of this ecosystem type is already included in existing conservation protected areas such as Kayan-Mentarang National Park. ** The goal for these targets is set higher than recommended for widespread target systems because their current areas have been greatly reduced in extent in just the last 50 years. The percentages also reflect that we are seeking “viable occurrences” which already limits the amount that can be captured meeting these criteria given ongoing threats and habitat degradation. *** One example of a Major River would be selected for each of the four stratigraphic units. Priority Setting (Ranking) of Target Ecological System Occurrences Terrestrial targets Evaluating and then ranking a group of factors related to actual or potential viability of the terrestrial conservation target occurrences facilitated setting priorities for these targets. In the U.S., rankings would normally be generated by Natural Heritage Programs or through expert advice that would suggest the area required for a viable population of a target species to persist in, say, Limestone Rainforest occurrences – or the distance between Mangrove occurrences that would begin to exceed the functional range of the mangrove assemblage of birds. In East Kalimantan such information is generally lacking. Therefore, we grouped the value for each occurrence of an ecological system type based on where the value lies in the quartile distribution of all values for its type across the planning area. This grouping is based on the logic that the life history strategy of animals in East Kalimantan has evolved to reflect the habitat patch variability within the region. Target ecological system occurrences with smaller areas that fell in the lowest quartile could reasonably be expected to be less able to maintain viable populations of a suite of animals when compared to larger areas of that same system type that fell into the uppermost quartile. For example, a Mangrove occurrence that was a long distance from other Mangroves, such that it fell into the highest quartile for distance between occurrences, could be expected to have poor migration potential (both in and out) for mangrove birds, insects or primates compared to occurrences that were closer and fell into lowest (least distant) quartile. There is some difficulty with this logic when it comes to habitat occurrences that have been recently fragmented, such as Peat Swamp Forests and the matrix Lowland Rainforest. However, because the boundaries of these units in this assessment are defined by the subcatchment areas and not the existing actual patch size, recent incidents of fragmentation may not bias the statistics as much as might be supposed, except perhaps in the determination of condition, discussed later in this report. The occurrence factors considered are as follows: 1). Area Theory of nature reserve design argues that larger areas are better than smaller ones for the conservation of biological diversity. But, theories also suggests that several smaller areas of similar size grouped together within a large single area may, in some circumstances, be a preferred option, particularly if the risks of frequent burning, contagious disease vectors or other environmental factors relying on contiguity are high (SLOSS principle). It is unlikely in the case of Lowland Rainforest ecological dynamics that many disjunct habitat patches 22
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Ecoregional Assessment of Biological Diversity in East Kalimantan

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