Mpumalanga Biodiversity Conservation Plan Handbook - bgis-sanbi

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M P U M A L A N G A CHAPTER 4 - BIODIVERSITY SPATIAL ASSESSMENT TABLE 4.1: Biodiversity features and processes used in the aquatic biodiversity assessment FEATURE DESCRIPTION & IMPORTANCE EXTENT/SIZE Rivers – biodiversity types Ecoregion Level 2 types: surrogate for aquatic biodiversity 30 types; 28 666 km of rivers Rivers – functional types River signatures: surrogate for functional types of rivers 24 types; 120 675 km of rivers Seepage and valley bottom Wetlands classified into functional types, 113 628 wetlands; totalling wetlands then according to Ecoregion Level 2 (for biodiversity) 312 771 ha; 51 types Pan wetlands Classified into perennial & non-perennial pans, and Ecoregion Level 2 biodiversity template 23 922 ha of pans; 39 pan types Peat wetlands Known peat wetlands 77 point records Fish species Known distribution of 4 threatened fish species 908 km of river length Important pan clusters All pans buffered with 1 km, transformed and heavily 132 611 ha of important clusters fragmented areas removed (> 500 ha) Important wetland clusters Wetlands buffered with 1 km, transformed and 266 820 ha of important clusters heavily fragmented areas removed (>1000 ha) High water-production areas Catchments producing 50% of Mpumalanga’s runoff High water-production areas equate mapped as high water-production areas to 19% of MBCP planning domain Aquatic refugia Refuge areas for maintaining fish populations during times of drought Selected subcatchments Migration areas Areas important for maintaining fish migration Selected subcatchments HEALTHY SUBCATCHMENTS No direct measure of subcatchment condition was available so we used a combination of PESC and the extent of terrestrial transformation, as measures of subcatchment integrity. Present Ecological State Class (PESC) is the degree to which present ecological conditions of a catchment have been modified from natural (reference) conditions. The measure is based on an assessment of water quality, biotic indicators and habitat information. Results are classified on a 6-point scale, from Category A (largely natural) to Category F (critically modified). A limitation of this data set is that PESC was based only on the main rivers within a quaternary catchment, not the tributaries. Each subcatchment was assigned the PES category of the parent quaternary catchment. At the subcatchment level, the extent of habitat transformation is a good proxy for riparian integrity. Thus the extent of transformation was used as one of the surrogates for subcatchment integrity because in heavily transformed subcatchments, one can expect to have degraded wetlands and tributaries. So the MBCP used a combination of PESC and habitat transformation for each subcatchment to identify healthy subcatchments. This output was used in Marxan to bias the selection of planning units Biodiversity to meet targets in these healthy subcatchments first. CONSERVATION PLAN HANDBOOK 25 SPATIAL ASSESSMENT
MPUMALANGA BIODIVERSITY CONSERVATION PLAN HANDBOOK FIGURE 4.1: Subcatchment health or integrity. The health was determined using a combination of PESC and subcatchment transformation values. The subcatchment health is summarised into 3 broad categories. These are then further displayed using the degree of transformation as shading. The darker the colour, the more transformed the subcatchment. RESULTS OF THE ASSESSMENT The smallest and most efficient portfolio of planning units that meets the targets for all aquatic features was determined using Marxan. The selection of these units was biased towards meeting targets in healthy subcatchments. The results show that 28% of Mpumalanga is identified as important for meeting aquatic biodiversity targets (in addition to protected areas). However, not 26 M P U M A L A N G A all of this area is in a healthy state. Of the additional required catchments, only 57% are healthy; 30% moderate and 13% Biodiversity modified. This implies that rehabilitation is needed in order to adequately conserve freshwater biodiversity within healthy subcatchments. CONSERVATION PLAN HANDBOOK
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Mpumalanga Biodiversity Conservation Plan Handbook - bgis-sanbi

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