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PRIORITISING QUATERNARY CATCHMENTS FOR INVASIVE ALIEN PLANT CONTROL WITHIN THE WORKING FOR WATER FREE STATE REGION: PROJECT REPORT
March 2011
Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State Region
Greg G. Forsyth, Patrick J. O’Farrell and David C. Le Maitre
CSIR Natural Resources and the Environment P.O. Box 320 Stellenbosch 7599, South Africa.
Report number: CSIR/NRE/ECO/ER/2011/0039/B March 2011
Prepared for: Andrew Wannenburgh Working for Water Programme Private Bag X4390 Cape Town 8000 Tel: 021 441-2738 E-Mail:
[email protected]
Contact person: Gregory Forsyth Tel: 021 888-2406 Fax: 021 888-2684 Email:
[email protected]
Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
Executive Summary Introduction Invasive alien plant control requires the allocation of limited resources to control operations to maximise benefits. The priorities for such allocation are based on a mixture of fact and opinion, interpreted either subjectively or objectively, and often not transparent or repeatable. This project develops an approach that could assist managers and planners in the Working for Water Programme’s Free State Region to prioritise their activities with a degree of transparency. We used the Analytic Hierarchy Process (AHP) to facilitate prioritisation. AHP is a multiple criteria decision-making tool for setting priorities when both qualitative and quantitative aspects of a decision need to be considered, and for achieving group consensus.
Priorities in the Free State Regional area A total of 155 quaternary catchments occur within two primary catchments that make up the Working for Water Programme’s Free State region, and were used in this assessment. The five quaternary catchments with the highest relative importance are D21E, D31E, D21G, D21D, C51K. The highest priority catchments for targeting the clearing of invasive alien plants fall into two areas of the region. Those catchments located in the high rainfall upper catchments of the Caledon and Wilge rivers and those in the dry south west part of the Free State. In the wetter areas the traits of the invasive alien plants in terms of water usage, aggressiveness, ease of control and how they change fuel properties are most important, as are high water yielding catchments, the condition of the rivers and available grazing responses. In the drier areas of the province high levels of dependence on ground water resources, grazing resources and surface water stressed areas. In general the highest priority catchments are those invaded by aggressive, difficult to control invasive alien plants, have high surface water yields and where most rivers are in a relatively
good ecological state. In the drier parts of the province high ground water demand and grazing are the most important criteria.
Conclusions and recommendations This study of the Free State region has successfully applied the approach developed by van Wilgen et al. (2008). In this case this has been done at a quaternary catchment scale. However, a number of follow-up actions will be needed if this approach is to deliver its full potential in terms of assisting the Working for Water Programme to improve its operations and its impact. We recommend the following: • That the techniques developed at this quaternary catchment scale be adopted by Working for Water’s national and regional planning offices to assist with prioritisation, planning, and the allocation of resources to both existing and new projects on an ongoing basis. •
The priorities identified here should be used to guide the allocation of funds between quaternary catchments and subcatchments of Free State region.
•
That a spatial database be developed to underpin effective comparisons of areas. This database should contain data relating to most of the criteria identified here, including continuous areas for grazing and specially the current condition of the grazing resource, groundwater demand and recharge, surface water stress, biodiversity conservation, soil potential, fire regime, harvestable products.
•
Each Working for Water region should maintain existing datasets and revise them on a regular basis. This period between revisions should not be longer than 3 years so as to coincide with the medium term expenditure framework of government.
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
Acknowledgements We thank the Working for Water Programme of the Department of Water and Environment Affairs for funding this work. We thank Mr Cedric Singo and Mr Andrew Wannenburgh of the Working for Water Programme of the Department of Water and Environment Affairs for supporting the project and serving on the reference group. The following managers, implementing agents and researchers are thanked for their informed and enthusiastic participation in the workshop aimed at developing a model for assessing the priority quaternary catchments to clear in the Free State Working for Water Region: Cedric Singo, Kefilwe Disipi, Makolane Mofokeny, Bornett Matoto, Simaei Patrick, Eliot Lithudzha, D.R. Moha, Z. Mokgalagadi, Peter Hawley, Jan Richter, Chris Smith, Neiukalo Thirsawanga, Nokulunga Mahlangu, Shamley Mogale, Paul Mazwi, Izak Venter, Hanlio Klopper, Elize Pienaar, Malcolm Procter, Johan Zeelie and Thami Gugushe. We also thank our colleague, Dr Brian van Wilgen, for reviewing this document.
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
Contents Executive Summary........................................................................................................................................................... i Acknowledgements ...........................................................................................................................................................ii Contents ...........................................................................................................................................................................iii Figures.............................................................................................................................................................................. v Tables...............................................................................................................................................................................vi 1. INTRODUCTION
1
2. SCOPE OF WORK
1
3. APPROACH
4
3.1
WORKSHOP TO DETERMINE RANKING CRITERIA
4
3.2
SPECIES SELECTION
4
3.3
GOAL AND CRITERIA
4
3.4
SELECTING APPROPRIATE DATA
3.4.6 Soil potential 3.4.7 Fire regime 3.4.8 Harvestable products
5 5 5 5 6 6 6 6 6 6 7 7 7 8 8 8 8 8 8 8 9 9 9 9 9 10 10
3.5
SPATIAL DATA SETS USED IN THE PRIORITISATION
10
3.6
CALCULATING THE WEIGHTS USED BY THE EXPERT CHOICE SOFTWARE
12
3.4.1 Presence of priority invasive alien plants
3.4.1.1 3.4.1.2 3.4.1.3 3.4.1.4 3.4.1.5
Aggressive invasive alien species Water use Ease of control Potential to invade Poisonous to livestock and humans
3.4.2 Continuous areas for grazing
3.4.2.1 3.4.2.2
Current condition for grazing Grazing potential
3.4.3 Groundwater integrity
3.4.3.1 3.4.3.2
Groundwater recharge Ground water importance
3.4.4 Surface water integrity
3.4.4.1 3.4.4.2
Water stress Water yield
3.4.5 Biodiversity conservation
3.4.5.1 3.4.5.2 3.4.5.3 3.4.5.4 3.4.5.5 3.4.5.6 3.4.5.7
Rangeland current condition Rangeland conservation value River condition River conservation value Wetland current condition Wetland conservation value Fallow land restoration
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
4. RESULTS
12
4.1
GOAL AND CRITERIA
12
4.2
FREE STATE PRIORITY QUATERNARY CATCHMENTS
14
5. CONCLUSIONS
21
6. RECOMMENDATIONS
22
7. REFERENCES
23
Appendix 1
Priority invasive alien plants in the moist savanna and grassland biomes for the Free State province
Appendix 2
Agenda for Free State region
Appendix 3
Participants in expert workshops
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
Figures Figure 1:
A map showing the regional boundaries of the Working for Water program in the Free State region, the biomes, savanna (arid and moist), Nama karoo and grassland, and the major towns in the region. _________________________________ 3
Figure 2:
A map showing the regional boundaries of the Working for Water programme in the Free State region, major towns and the primary catchments found in this region. _____ 3
Figure 3:
The relative importance and ranking of the 45 top priority quaternary catchments out of the 155 in the Free State Region. These values have been normalised. ______ 15
Figure 4:
The relative importance of quaternary catchments in the Free State region for each of the eight criteria that were assigned the highest importance in the model. The importance or weight is shown in parentheses._______________________________ 16
Figure 5:
The relative importance of quaternary catchments in the Free State region for the 9th to 16th most important criteria in the model. The importance or weight is shown in parentheses.________________________________________________________ 17
Figure 6:
The relative importance of quaternary catchments in the Free State region for the 16th to 24th most important criteria in the model. The importance or weight is shown in parentheses.________________________________________________________ 18
Figure 7:
The priority quaternary catchments identified according to priority classes within the Free State Region. Priority weightings reflect the scores for each catchment. The locations of current Working for Water control projects are also shown.____________ 19
Figure 8:
The expenditure allocated to invasive alien plant clearing projects in the Free State region in 2010/11, in relation to priorities identified in the study (Current exp.). Clearly, most quaternary catchments, including several of high priority, do not receive any funding. The figure also shows the amount of funding that would be allocated to each catchment if the allocations were proportional to priorities (Exp. according to priority), as well as the funding that would be allocated to each catchment (Top 16 priorities) if the allocation went to the 16 catchments with the highest priority.________________________________________________________ 20
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
Tables Table 1:
Grazing potential ranges and associated midpoints in large livestock units (LSU) per km2 (Scholes 1998).__________________________________________________ 7
Table 2:
Spatial datasets used to rank quaternary catchments in relation to selected criteria and sub-criteria. _______________________________________________________ 11
Table 3:
Identified criteria and descriptions of the attributes that they incorporate. __________ 12
Table 4:
Nested criteria, together with the relative weightings, identified for prioritising quaternary catchments in the Free State region for the clearing of invasive alien plants._______________________________________________________________ 13
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
1. INTRODUCTION Invasive alien plant control requires the allocation of limited resources to control operations to maximise benefits. The priorities for allocating resources typically are based on a mixture of fact and informed opinion and this information may be interpreted either subjectively or objectively. However, the information and the rationale behind the resulting priorities are rarely made explicit so it is difficult to assess the validity of the resulting priorities. The Council for Scientific and Industrial Research (CSIR) has recently completed studies on the prioritisation of primary catchments for the purposes of guiding invasive alien plant control operations. These included an assessment of the terrestrial biomes of South Africa and the established national priorities (van Wilgen et al., 2008), and others that have focused on quaternary catchment scale and established priorities for the Northern Cape and Western Cape (Forsyth et al., 2009, Le Maitre & Forsyth 2010). These studies developed an approach and method that enables managers and planners in the Working for Water Programme to prioritise their activities in a way that is transparent, logical and defensible. A biome-level study has also been undertaken and developed methods for the identification of a priority list of (i) invasive alien plants, and (ii) areas (primary catchments) within the terrestrial biomes of South Africa that should be targeted for control by the Working for Water Programme. Mr Andrew Wannenburgh of the Department of Water Affairs (DWA) asked the CSIR to assist in prioritising areas to clear within the Working for Water region in the Free State province by applying the methods developed for the biomes and the quaternary catchment scale studies. This report presents the results of this study to determine the priority quaternary catchments to clear within the Free State region. We also make recommendations for further improvements to the prioritisation process and its implementation by the Working for Water Programme.
2. SCOPE OF WORK This project is conducted as part of a collaborative agreement between the Department of Water Affairs’ Working for Water Programme and the CSIR. The work was guided and reviewed by a reference group, appointed by Working for Water, at the initiation of the project, in terms of the collaborative agreement. Members of the reference group were: •
Mr Cedric Singo (Working for Water Programme, Free State)
•
Mr Andrew Wannenburgh (Working for Water Programme, National)
It was agreed at the outset of the study that the planned scope of activities would be as follows: •
The work would focus on the three biomes that dominate the region, grassland, arid and moist savanna and nama karoo (Figure 1).
•
The work would entail prioritising areas to clear at a quaternary catchment scale within the portions of the Vaal catchment (C) and the Orange river (D) which occur in the Working for
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
Water regional boundaries of the Free State Province. We selected all the quaternary catchments which fall within this boundary (Figure 2). •
The Analytic Hierarchy Process (AHP)1 would be used to facilitate the prioritisation of quaternary catchments using Expert Choice 11.5 decision support software (Anonymous 2009).
•
The criteria to use for prioritising the quaternary catchments for the clearing of invasive alien plants would be identified and agreed to at an expert workshop to be held in or near Bloemfontein.
•
An obvious criterion was whether or not priority alien invasive species are present or likely to spread in a quaternary catchment. In this regard it was agreed that we would start with the list of priority species identified for the both the moist and arid savanna, nama karoo and the grassland (see Appendix 1) by the recent CSIR study (van Wilgen et al., 2008). In the Free State Province study we used data from National Invasive Alien Plant Survey (NIAPS) (Kotzé et al. 2010) for prioritising quaternary catchments based on the current extent and density of invasions. The NIAPS was undertaken by the Agricultural Research Council (ARC) and used an ecotope classification to extrapolate from the point samples to landscapes.
•
The work of Rouget et al. (2004) and Mgidi et al. (2007) would be used if necessary to identify areas that are likely to become invaded by the species identified in the CSIR study as priority species for clearing.
•
Where applicable and available we would also made use of river (Nel et al. 2007; Nel et al. 2011) and terrestrial (Driver et al. 2005) conservation prioritisation datasets for various spatial scales.
•
The assessment would focus on (a) the criteria and (b) the relative weighting of those criteria that will be used in prioritising the quaternary catchments and not on direct pair-wise catchment comparisons. The primary reason for this is that the AHP approach requires a pairwise ranking and there are too many quaternary catchments in the primary catchments of the Free State Province to make this feasible. We would therefore apply the procedures which we developed for automating these comparisons for the Western and Northern Cape Studies (Forsyth et al., 2009, Le Maitre & Forsyth 2010).
The Working for Water Programme’s strategic plan for 2008 – 2012 lists “the reduction of impact of existing priority invasive alien plant problems” as one of three primary goals relating to natural resource management. The other two are related to preventing problems, and building capacity to address problems. This project will assist in the identification of such priorities at a quaternary scale in the Free State region, which are not clearly defined at present.
1
AHP is a multiple criteria decision-making tool for setting priorities when both qualitative and quantitative aspects of a decision need to be considered. It involves setting a goal, breaking it down into its constituent parts and then assigning relative weights to each of these, thereby progressing from the general to the specific. Scoring is on a relative basis comparing one choice with another. Relative scores for each choice are computed with each level of the hierarchy. Scores are then synthesised through a model contained in Expert Choice. This yields a composite score for each choice at every level as well as an overall score.
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
Figure 1: A map showing the regional boundaries of the Working for Water program in the Free State region, the biomes, savanna (arid and moist), Nama karoo and grassland, and the major towns in the region.
Figure 2: A map showing the regional boundaries of the Working for Water programme in the Free State region, major towns and the primary catchments found in this region.
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
3. APPROACH 3.1 WORKSHOP TO DETERMINE RANKING CRITERIA A one day workshop was held in Bloemfontein on 20th January 2011. The workshop agenda is provided in Appendix 2. A total of 22 people from the key economic sectors, including, Conservation, Agriculture and Water Affairs as well as the Working for Water representatives responsible for implementing Working for Water projects, participated in the workshop (see Appendix 3). The topics addressed at the workshop were: •
Findings from previous studies conducted by the CSIR at a regional or provincial level in the Northern Cape and the Western Cape (Forsyth et al. 2009; Le Maitre & Forsyth 2010)
•
An explanation of the Analytic Hierarchy Process
•
Current priority invasive alien plants for the savanna, grassland, and karoo biomes (See Appendix 1)
•
The goal, criteria (objectives) and sub-criteria (sub-objectives) for prioritising quaternary catchments. These were captured on paper and using the Expert Choice software
•
Pair-wise comparisons (ranking) of the agreed criteria and sub-criteria using the Analytic Hierarchy Process approach in the Expert Choice software
•
Identifying the datasets that will allow for the objective comparison of quaternary catchments with regard to particular criteria
3.2 SPECIES SELECTION Workshop participants undertook a species verification exercise. Here local experts examined and commented on the lists of invasive species identified by van Wilgen et. al (2008; 2010) for the savanna, grassland and karoo biomes. A consolidated list was created which included those verified species as well as additional species which participants felt were problematic. The result was a complete list of the most important alien species for the Free State Province. These are presented according to the regions biomes in Appendix 1.
3.3 GOAL AND CRITERIA The workshop participants established a goal for prioritizing the clearing of catchments in within the Free State region. Criteria for meeting this goal were also developed and weighted in relation to one another. The AHP was used to compare each individual criterion to each other and to assign weightings to each of these according to their relative importance (Saaty, 1990). The Expert Choice software package, based on AHP, was used to facilitate this process (Anonymous 2009).
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
3.4 SELECTING APPROPRIATE DATA A summary of the data sets used, the rationale for using these to address the criteria underlying the hierarchy mode and methods are provided below. We were limited in our choice to those datasets that were readily available (in the public domain) and covered the entire Working for Water Free State region. We did not rely on expert opinion in palace of data sets. Where no data was available we used surrogate measures or related variables. Where this was not possible we gave all quaternary catchments the same value.
3.4.1
Presence of priority invasive alien plants
3.4.1.1 Aggressive invasive alien species The aggressiveness score was based on the multiplying the following values: (a) seed dispersal (3 = Long range (wind, bird, water); 2 = Short range; 1 = No seeds); (B) growth rate (3= fast, 3= moderate, 1= slow); (c) numbers of seeds produced (3 = high, 2 = moderate; 1 = low or none); sprouting (2 = sprouter; 1= non-sprouter). The score ranged from 72 (e.g. Acacia mearnsii) to 4 (e.g. Populus species). These scores were multiplied by the condensed invaded area for each priority species in each quaternary catchment and divided by the total condensed invaded area for that catchment to give an area weighted mean aggressiveness score per species.
3.4.1.2 Water use This criterion identifies the importance of increasing water resource availability by controlling invasive alien plants. We used the priority species for the Free State region from the national invasive alien plant survey (Kotzé et al. 2010) (Appendix 1). The water-use score is derived from the Versfeld et al. (1998) biomass-based model classification and incorporates new knowledge about water-use by Lantana camara, Chromolaena odorata, Arundo donax and other species based on the Surface Energy Balance (SEBAL) model estimates of evaporation from stands of invasive species (Meininger and Jarmain 2009) and other studies (Dye and Jarmain 2004; Dye et al. 2008). The water use classification is as follows:
•
Class 3 = Tall trees (e.g. wattles, eucalypts, pines poplars) and other high‐water users (e.g. Lantana camara, Arundo donax)
•
Class 2 = Medium trees (e.g. Prosopis species, Melia azederach)
•
Class 1 = all other species
Class 3 species were given a score of 3, class 2 a score of 2 and class 1 a score of one. These scores were multiplied by the condensed invaded area for each priority species in each quaternary catchment based on the national invasive alien plant survey (Kotzé et al. 2010). The species scores were summed and divided by the total condensed invaded area for that catchment to give an area weighted mean water use score per catchment.
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3.4.1.3 Ease of control The ease with which one controls invasive alien plants is influenced by a number of factors including sprouting ability, seed production, persistence of seed, and reproductive maturation. We used the product of the following: (a) sprouting ability (3 = vigorous, 2 = weak, 3 = none), number of seeds produced (3 = numerous, 2 = moderate, 1 = few or none), persistence (longevity) of the seedbank (3 = very long lived, 2 = moderately long-lived, 1 = short-lived or none), reproductive maturation (3 = fast, 2 = slow, 1 = no seeds). The resulting scores range from 3 for Salix babylonica to 81 for Acacia mearnsii. The species scores were multiplied by the condensed invaded area for each priority species in each quaternary catchment and divided by the total condensed invaded area for that catchment to give an area weighted mean ease of control score for each catchment.
3.4.1.4 Potential to invade We estimated the potential for future invasion by priority species using the combined list that was generated at the workshop. Data on the potential ranges (invasion envelopes) have been developed for a range of species by Rouget et al. (2004), and we made use of this data. We determined the number of priority species that could invade the remaining natural vegetation in a quaternary catchment based on the biome composition of that catchment (grassland and savanna). We assigned the greater of these two biome values to the catchment. The quaternary catchment with the highest number of species received the weight based on this species number.
3.4.1.5 Poisonous to livestock and humans We have been unable to develop a valid method of calculating the effects that alien invasive species are having on human and animal health from a spatial prioritisation perspective. We have therefore weighted all quaternary catchments within this region as being equal with regards to this criterion.
3.4.2
Continuous areas for grazing
3.4.2.1 Current condition for grazing In assessing grazing induced degradation we calculated the area of degraded and eroded veld within each quaternary catchment from the 2000 national land cover dataset (Van den Berg et al. 2008). The total area of degraded and eroded land was then subtracted from the total natural veld area in each catchment. This then gave us an area per catchment of veld in a good condition and this was expressed as a proportion of the quaternary catchment.
3.4.2.2 Grazing potential The relative value of the land for livestock production was estimated by calculating the grazing potential of quaternary catchments. This potential was derived from Scholes’ (1998) estimates of sustainable mean domestic livestock production (Table 1). This approach may underestimate the carrying capacity for browsing antelope but as game farming only occurs in limited areas this would not significantly affect the outcome.
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
Table 1: Grazing potential ranges and associated midpoints in large livestock units (LSU) per km2 (Scholes 1998).
LSU range LSU mid‐point
0 – 1 0.5
1 – 2 1.5
2 – 3 2.5
3 – 4 3.5
4 – 6 5
6 – 8 7
8 – 10 9
10 – 14 12
14 – 18 16
18 – 22 20
We assumed that only untransformed (natural) vegetation would support livestock, and subtracted the area of transformed vegetation, using the National Land Cover Database 2000, (Van den Berg et al. 2008) from the carrying capacity layer (Scholes 1998) in each catchment before the above calculation was made. We took the midpoint of each class, and multiplied it by the remaining area in that class in each quaternary catchment to get an area weighted mean grazing capacity. Catchments were ranked according to weighted grazing capacity, with the highest rank being given to those with the greatest capacity.
3.4.3
Groundwater integrity
Ground water data for the prioritisation studies were taken from the Groundwater Resource Assessment Project of the Department of Water Affairs (DWAF 2005). The study included estimates of the groundwater recharge, groundwater exploitation potential and the groundwater demand at various spatial scales including quaternary catchments. The objective behind this criterion was to secure the sustainable provision of ground water by controlling alien invasive plants. We used ground water recharge and ground water importance (demand) as these are key components of the sustainable use of groundwater.
3.4.3.1 Groundwater recharge Groundwater recharge was estimated from mean annual rainfall and hydrogeological data, and information from recharge studies by Groundwater Resource Assessment Phase 2 study (DWAF 2005). Summary data are available for quaternary catchments which give estimates of the mean annual recharge (millions of m3 per year). These data were converted to give the mean annual recharge per catchment in millimeters. The recharge (mm) was used as the weight for each catchment, with the greatest weight going to catchments with the greatest depth of recharge.
3.4.3.2 Ground water importance All water users have to register their planned water-use with the Department of Water Affairs as part of their obligations under the National Water Act. The registration database gives an indication of the potential groundwater-use by the users found in each quaternary catchment. In practice the users register for as much water as they could possibly use without regard for the actual amount that is available on a sustainable basis. The Groundwater Resource Assessment Project (DWAF 2005) provided estimates of the registered use as a percentage of the recharge in each quaternary catchment. This is also the best estimate we have of the demand although in many cases demand is far greater than the total recharge (i.e. >100%) and not achievable in practice. We have used the demand expressed as percentage of the recharge as an indication of the dependence of the water-users in that catchment on groundwater. Catchment with a high
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percentage demand received the greatest weights for both groundwater demand and groundwater dependence. 3.4.4
Surface water integrity
3.4.4.1 Water stress We included a sub-criterion for water stress to assign catchments with little or no water availability a higher priority. The best estimate we could find for overall water stress was the annual yield balance calculated by the Department of Water Affairs’ Water Situation Assessment Model (WSAM 2003) which was specifically set up to compare the yields available from water supply systems and relate them the demand. Negative values represent a high water demand (i.e. demand exceeds yields) but we need negative values to be given a high priority. The positive values were converted to negative and vice versa so the greatest deficit has a positive value. Then the lowest value was added to all the values to make the full series positive. The catchments with the greatest demand received the highest value and the greatest proportional weight.
3.4.4.2 Water yield Surface water run-off information was obtained from the Water Resources 2005 quaternary catchment dataset (Middleton and Bailey 2008). We used the naturalised mean annual run-off per catchment and ranked them in order of naturalized run-off.
3.4.5
Biodiversity conservation
3.4.5.1 Rangeland current condition In assessing ecosystem function and services we used areas of natural land cover as a surrogate measure. We calculated the area of untransformed land in each quaternary catchment from the 2000 national land cover dataset (Van den Berg et al. 2008). This was done by removing all transformed land classes from the dataset, which included all cultivated land and improved grassland; all urban and industrial areas, mining and quarries and water storage dams. We calculated the area of remaining natural vegetation in each quaternary catchment and expressed this as a proportion of the area of the catchment.
3.4.5.2 Rangeland conservation value We used vegetation status as a measure of the requirements for terrestrial conservation in this region. Vegetation conservation status based on the most recent conservation status assessment (DEA 2009) was used to update the 2004 status used in the national vegetation map (Mucina and Rutherford 2006). Once all transformed areas had been removed from the region, the total area of each vegetation status class was expressed as a proportion of the total area of each quaternary catchment. Weights were in proportion to the area of threatened vegetation.
3.4.5.3 River condition To assess river condition we used the National Freshwater Ecosystem Priority Area (NFEPA) rivers data (Nel et al. 2011) which summarizes river condition that was used in deriving freshwater
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ecosystem priority areas for river ecosystems. In prioritising for river systems which are completely natural, slightly or moderately modified we selected only rivers with an identified condition category of A = Unmodified, natural, B = Largely natural with few modifications, AB = A or B, C = Moderately modified. The remaining NFEPA river condition categories were given a 0 value and we allocated all river lengths to quaternary catchments. We calculated the total length of these relatively natural rivers for each quaternary catchment. This summed length was then divided by the summed length for all the rivers in a catchment, thereby calculating the proportion of natural rivers for each catchment. Catchment with the highest proportion of natural rivers received the highest weighting.
3.4.5.4 River conservation value We determined areas of conservation significance from the NFEPA data (Nel et al. 2011). Areas identified as Fresh Water Ecosystem Priority Areas and Fish Support Areas were selected and their area calculated as a proportion of each quaternary catchment. Catchments with greater proportional areas of these fresh water ecosystem priority areas were assigned higher weights.
3.4.5.5 Wetland current condition The NFEPA data and atlas (Nel et al. 2011) has assigned each wetland within the country a wetland condition category. These categories are AB =good or natural condition, C = moderately modified, D = wetlands associated with degraded rivers, Z = artificial or critically modified area. We associated wetland condition scores to each of these wetlands with AB = 3, C=2, DEF=1, and all Z values =0. We then calculated the areas of wetlands within each category for each quaternary catchment, multiplied these area by their wetland scores. These values where then summed according to quaternary catchments and proportioned according to the sum of the areas of the first three categories. Wetlands with the best quality (proportioned per catchment) received the highest weighting.
3.4.5.6 Wetland conservation value Wetland conservation value was calculated from the NFEPA data (Nel et al. 2011) where wetlands were identified as either being of conservation importance or not. We assigned all wetlands to quaternary catchment. The total area of wetlands of conservation importance was expressed as a proportion of the respective quaternary catchment. Catchments having the highest proportion received the greatest weight.
3.4.5.7 Fallow land restoration We were unable to find any suitable spatial data to represent this criterion. We have therefore weighted all quaternary catchments within this region as being equal with regards to this criterion.
3.4.6
Soil potential
We used the Land capability data (ARC 2002) to determine the soil potential of areas within this region. This database divides the national land surface into eight classes, ranging from 1 = Very high agricultural potential to 8 = Very low agricultural potential. We apportioned quaternary catchments into areas of different land soil potential using the land capability database once all
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
transformed areas were removed. We multiplied the area under each of the classes by the number of the class (1 to 8), summed these scores for the quaternary catchments and divided by the area of the quaternary catchment. We then subtracted all values from highest category value (8), to reverse the order of scores, making the area with the highest score as having the most potential for cultivation and visa versa.
3.4.7
Fire regime
This criterion identifies the potential to remove the risk of increased fuel loads by controlling invasive alien plants in catchments. We estimated this using the condensed area of invasive plant species within quaternary catchments in the Free State region derived from the NIAPS dataset (Kotzé et al. 2010). The fuel score rated species in terms of the fuel load they typically generate from low = 1 (e.g. Agave species) to moderate = 2 (e.g. Acacia melanoxylon) to high = 3 (e.g. Acacia cyclops). These scores were multiplied by the condensed invaded area for each priority species in each quaternary catchment and divided by the total condensed invaded area for that catchment to give an area weighted mean fuel load index per catchment.
3.4.8
Harvestable products
We were unable to obtain spatial data on areas where there is currently harvesting of medicinal plants, indigenous fire wood, thatching and materials for hand crafts. In the other Working for Water regions we used the study by Naudé et al. (2007) which described the functioning of settlements in South Africa in terms of a rural – urban typology. They assigned values corresponding to the dominant settlement type to each of approximately 25 000 irregularly shaped mesozones (approximately 49 km2 or 7 km by 7 km in size) in South Africa. One of the settlement types recognised is “dispersed rural settlements”. Most of these settlements are located in the rural areas of South African that were previously referred to as “homelands”. They typically have high population densities but are distant from formal employment opportunities and social services. This implies a high degree of dependence on the utilization natural veld products to sustain their livelihoods. In the Free State only two of the 155 quaternary catchments have mesozones of this type. We found when we included this in the model that it skewed all the outputs. We were also unable to develop a valid method of calculating the effects that alien invasive species are having on bee keeping from a spatial prioritisation perspective. We have therefore weighted all quaternary catchments within this region as being equal with regards to this criterion.
3.5 SPATIAL DATA SETS USED IN THE PRIORITISATION The prioritisation of the catchments relies on matching of criteria data sets that either provide a direct measure of the criterion, or a surrogate measure where direct data are not available (Table 2).
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
Table 2: Spatial datasets used to rank quaternary catchments in relation to selected criteria and sub-criteria.
1
Criterion
Sub-criterion
Spatial data
Presence of priority Invasive Alien Plants
Aggressive invasive alien species
South African Plant Invaders Atlas (Henderson 1998 and revisions) - copy of database March 2010
Water use
National Invasive Alien Plant Survey (Kotzé 2010)
Ease of control
National Invasive Alien Plant Survey (Kotzé 2010)
Potential to invade
Rouget et al. (2004) and Mgidi et al. (2007) only of potential
Poisonous to livestock and humans
None available
Current condition for grazing
National Land Cover Database 2000 (Van den Berg et al. 2008)
Grazing potential
Areas of homogenous grazing potential (Scholes 1998)
Groundwater recharge
Groundwater resource assessment project (DWAF 2005)
Ground water importance
Groundwater resource assessment project (DWAF 2005)
Water stress
Water Situation Assessment Model (WSAM 2003)
Water yield
Water Resources 2005 (Middleton & Bailey 2008)
Rangeland current condition
National Land Cover Database 2000 (Van den Berg et al. 2008)
Rangeland conservation value
National Vegetation Map (Mucina and Rutherford 2006) updated with the 2009 threatened ecosystem list (DEA 2009). Environmental Potential Atlas (ENPAT 2001)
River condition
National freshwater ecosystem priority areas (Nel et al. 2011)
River conservation value
National freshwater ecosystem priority areas (Nel et al. 2011)
Wetland current condition
National freshwater ecosystem priority areas (Nel et al. 2011)
Wetland conservation value
National freshwater ecosystem priority areas (Nel et al. 2011)
Continuous areas for grazing
Groundwater integrity
Surface water integrity
Biodiversity conservation
Fallow land restoration
None available
Soil potential
National land capability (ARC 2002); National Land Cover Database 2000 (Van den Berg et al. 2008)
Fire regime
National Invasive Alien Plant Survey (Kotzé 2010)
Harvestable products
1
Medicinal plants
None available
Bee keeping (pollen and nectar)
None available
Indigenous fire wood sources
None available
Thatching and hand crafts
None available
See Section 3 above for descriptions of how these datasets were used and see the reference section for complete references.
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
3.6 CALCULATING THE WEIGHTS USED BY THE EXPERT CHOICE SOFTWARE The Expert Choice software (Anonymous 2009) calculates the weights of alternatives (quaternary catchments in this case) as proportions that sum to one. For each of the criteria and sub-criteria used by the AHP model we calculated the sum of the values for each variable for each quaternary catchment. Each quaternary catchment’s value for that variable was then divided by the corresponding total to give the final weight.
4. RESULTS 4.1 GOAL AND CRITERIA The goal that that was agreed on at the Bloemfontein workshop was “To control invasive alien plant species to optimise the utilisation of natural resources and to conserve biodiversity”. Goal setting was followed by the identification of six criteria for prioritising the clearing of quaternary catchments within the Free State region. The criteria identified were: Presence of priority invasive alien plants, continuous areas for grazing, groundwater integrity, surface water integrity, biodiversity conservation, soil potential, fire regime, harvestable products. Descriptions of these criteria are provided (Table 3). Many of the criteria were further divided into sub-criteria, for example, the criterion “biodiversity conservation” was divided into the sub-criteria of rangeland conservation, river conservation and wetland conservation, and these were both further sub divided into sub-sub-criteria. The final ranking for prioritisation, considering all the criteria, sub-criteria and sub-sub-criteria is provided (Table 4). Table 3: Identified criteria and descriptions of the attributes that they incorporate.
Criterion
Description
Presence of priority invasive alien plants
The actual presence of invaders and their future invasion potential. The objective behind this criterion was to identify both areas with aggressive invaders, invaders where invaders are likely to use excessive water, identify area that are likely to become invaded it there is no control, those area were control is possible and optimal in terms of the density of invasions and where there are invasive species that are poisonous to both livestock and humans.
Continuous areas for grazing
The degree to which the alien species are able to displace indigenous species which are important for grazing. The objective behind this criterion was to retain and restore land capability for animal production.
Groundwater integrity
The degree to which alien plant species control will improve ground water resources. This includes ground water recharge and ground water importance. The objective behind this criterion was to secure the sustainable provision of ground water.
Surface water integrity
The degree to which alien plant species control will improve surface water resources. This includes water yield and water stress. The objective behind this criterion was to secure the sustainable provision of surface water.
Biodiversity conservation
The degree to which the alien species are able to displace indigenous species, in particular their impact on rangeland, river and wetland conservation. The objective behind this criterion was to protect biodiversity priority areas of these features.
Soil potential
The degree to which the alien species are able to impact on areas potentially important for future cultivation. The objective behind this criterion was to retain land
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
Criterion
Description capability.
Fire regime
The degree to which alien species is able to increase fuel loads posing a potential risk to natural and built capital. The objective behind this criterion was to identify the potential to remove the risk of increased fuel loads by controlling invasive alien plants in catchments where they have the greatest collective biomass and therefore fuel load.
Harvestable products
The degree to which the alien species are able to displace indigenous species which are important harvestable resources. The objective behind this criterion was to ensure the sustainable provision of these natural resources.
Table 4: Nested criteria, together with the relative weightings, identified for prioritising quaternary catchments in the Free State region for the clearing of invasive alien plants.
Criterion
Weighting assigned
Weighting assigned
Sub-criterion
(%) Presence of priority invasive alien plants species
Continuous areas for grazing
Groundwater integrity
Surface water integrity
Biodiversity conservation
(%) Aggressive invasive alien species
0.289
0.287
0.119
0.117
Water use
0.116
Ease of control
0.015
Potential to invade
0.012
Poisonous to livestock and humans Current condition for grazing
0.239 0.048
Groundwater recharge
0.03
Ground water importance
0.089
Water stress
0.078
Water yield
0.039
Rangeland conservation
0.038
Wetland conservation
0.06
Fire regime
0.03
Harvestable products
0.025
River condition
0.007
River conservation value Wetland current condition Wetland conservation value
0.004
Medicinal plants
0.016
Thatching and hand crafts
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Rangeland current condition Rangeland conservation value
0.024
Fallow land restoration
Bee keeping (pollen and nectar) Indigenous fire wood sources
(%)
0.05
Grazing potential
River conservation
Weighting assigned
0.096
0.073
Soil potential
Sub-sub-criterion
0.004 0.004 0.001
0.033 0.005 0.02 0.004 0.002 0.005
Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
The most important criterion to be identified was the presence of priority invasive alien plants, this was given a weighting of 28.9.8%, followed by protect continuous areas for grazing (28.7%), groundwater resource (11.9%), and surface water resource (11.7%). These four criteria accounted for 81.2% of the model. The remaining four criteria accounted for 18.8% of the weighting in achieving the goal. Biodiversity conservation, soil potential, fire regime, and harvestable products, were assigned weightings of 7.3%, 6%, 3% and 2.5% respectively.
4.2 FREE STATE PRIORITY QUATERNARY CATCHMENTS Within the Free State region the ten catchments with the highest relative importance rankings are: D21E, D31E, D21G, D21D, C51K, D21F, D23C, D23A, C81L, C22K (Figure 3). All criteria have been mapped according to quaternary catchments indicating priorities for each of these (Figures 4 - 6). Of the 155 quaternary catchments investigated, the first 10 accounted for just over 13% of the total weight of the priorities in the model. The priorities for quaternary catchments in the Free State region are shown in Figure 7. The highest priority catchments fall into two areas of the region. Those catchments located in the high rainfall upper catchments of the Caledon and Wilge rivers and those in the dry south west part of the Free State. In the wetter areas the traits of the invasive alien plants in terms of water usage, aggressiveness, ease of control and how they change fuel properties are most important, as are high water yielding catchments, the condition of the rivers and available grazing responses. In the drier areas of the province high levels of dependence on ground water resources, grazing resources and surface water stressed areas. Of the 16 quaternary catchments which currently have clearing projects in operation, two are in the top ten priority catchments identified while a total of five occur in the top 26 catchments. Figure 8 indicates that nine of the clearing projects are in catchments in the top third of the identified priority catchments, and three clearing projects are situated in catchments in very low priority areas.
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
D21E D31E D21G D21D C51K D21F D23C D23A C81L C22K C81A C81M C83F C81C C83D D23D D23E C83J D22B C81B D23J C51J C42H C24B C51C C81F D23G D22A C42C C81G C82A D23H C23B D22D D22G C13C C51F C83A C52K C83K C82F D22H C91C C82E D31D
1.00000 .77888 .77806 .77522 .72538 .70552 .65173 .64865 .60846 .60479 .58963 .58707 .56802 .56227 .54285 .53205 .52995 .52858 .52342 .50748 .49334 .48664 .46796 .46300 .45450 .45240 .44594 .44454 .44435 .43983 .43253 .43159 .42992 .42571 .42549 .42536 .42480 .42363 .42305 .42080 .41646 .41610 .41075 .40703 .40269
Figure 3: The relative importance and ranking of the 45 top priority quaternary catchments out of the 155 in the Free State Region. These values have been normalised.
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
Water use of invasive alien plants (0.116)
Current grazing condition (0.239)
N
N
Criterion weighting 0.001 - 0.004 0.004 - 0.005 0.005 - 0.007 0.007 - 0.008 0.008 - 0.009 0
50
100
150
Cri teri on wei ghting 0 - 0.002 0.002 - 0.006 0.006 - 0.012 0.012 - 0.02 0.02 - 0.045
2 00 Kilo me ter s
0
Aggresiveness of invasive alien plants (0.096)
50
10 0
15 0
20 0 Kilo me ter s
Groundwater importance (0.089)
N
N
Crit erion wei ghting 0 - 0.0 04 0.00 4 - 0. 016 0.01 6 - 0. 031 0.03 1 - 0. 046 0.04 6 - 0. 11
Cri teri on wei ghting 0 - 0.002 0.002 - 0.006 0.006 - 0.01 0.01 - 0.02 0.02 - 0.052 0
50
10 0
15 0
0
20 0 Kilomet er s
Water stress (0.078)
50
100
15 0
200 Kilomet ers
Soil potential (0.06)
N
N
Crit erion weigh tin g 0.002 - 0 .004 0.004 - 0 .006 0.006 - 0 .007 0.007 - 0 .008 0.008 - 0 .009
Criterion weighting 0 - 0.001 0.001 - 0.005 0.005 - 0.006 0.006 - 0.007 0.007 - 0.007 0
50
100
1 50
0
2 00 Kilome ter s
Poisonous to livestock and humans (0.05)
50
100
15 0
200 Kilo me ter s
Grazing potential (0.048)
N N
Criterion weighting 0.002 - 0.004 0.004 - 0.005 0.005 - 0.007 0.007 - 0.008 0.008 - 0.009
Cr iterion wei ghting 0.0065
0
50
10 0
15 0
20 0 Kilome ter s
0
50
10 0
15 0
20 0 Kilomet er s
Figure 4: The relative importance of quaternary catchments in the Free State region for each of the eight criteria that were assigned the highest importance in the model. The importance or weight is shown in parentheses.
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
Rangeland condition (0.033)
Water yield (0.039)
N
N
Crite rion weight n i g 0 - 0 .003 0 .003 - 0 .006 0 .006 - 0 .011 0 .011 - 0 .021 0 .021 - 0 .033 0
50
100
15 0
Cr iterion weigh ting 0.00 1 - 0.00 4 0.00 4 - 0.00 5 0.00 5 - 0.00 7 0.00 7 - 0.00 8 0.00 8 - 0.00 9
2 00 Ki l om e te rs
Groundwater recharge (0.03)
0
50
100
15 0
20 0 Ki o l m e te rs
Fire regime (0.03)
N
N
Cr ti erio n weig hting 0.00 2 - 0.0 03 0.00 3 - 0.0 05 0.00 5 - 0.0 08 0.00 8 - 0.0 12 0.01 2 - 0.0 19 0
50
100
150
Crite rion we ightin g 0 - 0. 003 0. 003 - 0 .008 0. 008 - 0 .014 0. 014 - 0 .024 0. 024 - 0 .057 0
200 Kil ometers
River condition (0.02)
50
1 00
1 50
2 0 0 Kil o me ter s
Medicinal plants (0.016)
N N
Cr iterion weigh ting 0 - 0.00 2 0.00 2 - 0.00 5 0.00 5 - 0.00 7 0.00 7 - 0.00 9 0.00 9 - 0.01 1 0
50
100
15 0
Cr iterion weigh ting 0.00 65
2 00 Ki l om e te rs
Ease of control of invasive alien plants (0.015)
0
50
100
15 0
2 00 Ki o l m e te rs
Potential to invade (0.012)
N
N
Crite rion weight n i g 0 - 0 .002 0 .002 - 0 .006 0 .006 - 0 .011 0 .011 - 0 .022 0 .022 - 0 .043 0
50
10 0
1 50
2 0 0 Ki l o me ter s
Cr iter ion weig hting 0 - 0.0 01 0.0 01 - 0.0 06 0.0 06 - 0.0 07 0.0 07 - 0.0 08 0.0 08 - 0.0 09 0
50
1 00
150
20 0 Ki o l m e te rs
Figure 5: The relative importance of quaternary catchments in the Free State region for the 9th to 16th most important criteria in the model. The importance or weight is shown in parentheses.
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
Wetland conservation value (0.005)
Rangeland conservation value (0.005)
N
N
Criterion weighting 0 - 0.004 0.004 - 0.012 0.012 - 0.024 0.024 - 0.04 0.04 - 0.057 0
50
1 00
15 0
Criterion weighting 0 - 0.003 0.003 - 0.012 0.012 - 0.026 0.026 - 0.093 0.093 - 0.28
20 0 Kilome ter s
0
50
100
1 50
2 00 Kilo me ter s
Indigenous fire wood (0.004)
Bee keeping (0.004)
N
N
Criterion weig hti ng 0.0065
Criterion weighting 0.0065 0
50
1 00
15 0
0
20 0 Kilomet ers
River conservation value (0.004)
50
100
150
20 0 Kilomete rs
Fallow land restoration (0.004)
N N
Criterion weighting 0 - 0.003 0.003 - 0.008 0.008 - 0.013 0.013 - 0.022 0.022 - 0.027 0
50
1 00
15 0
Criterion wei ghting 0.00 65
0
20 0 Kilomete rs
Wetland condition (0.002)
50
1 00
15 0
2 00 Kilomet er s
Thatching and hand crafts (0.001)
N N
Criterion weighting 0.003 - 0.005 0.005 - 0.006 0.006 - 0.007 0.007 - 0.007 0.007 - 0.008 0
50
10 0
15 0
20 0 Kilomete rs
Criterion weighting 0.0065 0
50
100
150
2 00 Kilo me ter s
Figure 6: The relative importance of quaternary catchments in the Free State region for the 16th to 24th most important criteria in the model. The importance or weight is shown in parentheses.
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
Parys Y # U %
Parys/Vredefort
Kroonstad Y #
Christiana Y #
Bultfontein U %
U Hertzogville % U %
U Paul Roux %
Bethlehem Y # UJordaan %
Boshoff
%% U U U%
Harrismith Y # U %
#
Marquard
#
U %
Petrusburg
U %
U %
Qwa-Qwa Golden Gate
Bloemfontein Y #
Clarens Ladybrand
U %
Luckhoff
Upper Wilge Van Reenen
#
U Dealsville % U %
#
#
U %
Jacobsdal
U %
N
Little Caledon
U Koffiefontein %
Y Towns # U WfW Projects - 2010 % Prioritiy quaternary catchment weightings 0.003 - 0.005 0.005 - 0.006 0.006 - 0.008 0.008 - 0.011 0.011 - 0.018
Vanderkloof # Y
0
50
100
150
200 Kilometers
Figure 7: The priority quaternary catchments identified according to priority classes within the Free State Region. Priority weightings reflect the scores for each catchment. The locations of current Working for Water control projects are also shown.
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Budget (Millions of
Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
Quaternary catchment priority ranking (1= most important to 155 =least important) Figure 8: The expenditure allocated to invasive alien plant clearing projects in the Free State region in 2010/11, in relation to priorities identified in the study (Current exp.). Clearly, most quaternary catchments, including several of high priority, do not receive any funding. The figure also shows the amount of funding that would be allocated to each catchment if the allocations were proportional to priorities (Exp. according to priority), as well as the funding that would be allocated to each catchment (Top 16 priorities) if the allocation went to the 16 catchments with the highest priority.
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
5. CONCLUSIONS This study has identified the highest priority quaternary catchments for managing invasive alien plants within the Vaal River and Orange River primary catchments which are managed by the Working for Water Free State region and compared them with the current budget allocations. There is some alignment between identified priority areas and the location of existing projects, however there is only one clearing project in the top five identified quaternary catchments. The regional Working for Water management team needs to assess how best to improve the current alignment between budgets and priority catchments over time. The techniques we have developed to determine the priority areas for clearing invasive alien plants at a quaternary catchment scale are workable but it is not really clear whether the results correspond with what the managers and experts would intuitively expect. The difference that this new approach makes is that the managers can now evaluate the roles of the individual data elements which contribute to each score assigned by the Expert Choice software and adjust them where necessary. An advantage of using the Analytic Hierarchy Process is that it can handle a large number of alternatives enabling comparisons to be made on any number of quaternary catchments. This study has identified a number of shortcomings regarding the available spatial data and, in other instances, the lack of appropriate spatial data to represent the criteria and sub-criteria that were considered important by the experts. In particular, the current condition of the grazing resource was given a high priority but we were unable to obtain suitable data in an appropriate format.
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
6. RECOMMENDATIONS This study has been successful in applying the approach developed by van Wilgen et al. (2008), Forsyth et al. (2009) and Le Maitre and Forsyth (2010), at a quaternary catchment scale in the Free State Region. However, a number of follow-up actions will be needed if this approach is to deliver its full potential in terms of assisting the Working for Water Programme to improve its operations and its impact. With this in mind, we recommend the following: •
That the techniques developed at the primary and quaternary catchment scale be adopted by Working for Water’s national and regional planning offices to assist with prioritisation, planning, and the allocation of resources to both existing and new projects on an ongoing basis. This would assist in establishing a uniform approach to prioritisation across the organization and allow for regular reassessments as needed and when new or improved datasets become available.
•
Future funding should be channelled into establishing invasive alien clearing projects in catchments that have been identified as having high priorities. In addition projects in low priority catchments should be brought to a conclusion.
•
Each Working for Water region should maintain existing datasets and revise them on a regular basis. This should not be longer than 3 years so as to coincide with the medium term expenditure framework of government.
•
That a spatial database be developed to underpin effective comparisons of areas. This database should contain data relating to most of the criteria identified here, including continuous areas for grazing and specially the current condition of the grazing resource, groundwater demand and recharge, surface water stress, biodiversity conservation, soil potential, fire regime, harvestable products. We recommend the development of datasets to address the most important of these deficiencies especially the current condition of the grazing resource as it was ranked as the most important criterion. The Working for Water Information Management System should be used to store the necessary data.
•
The results are as good as the underlying spatial datasets but as new or revised datasets become available they should be incorporated into the hierarchical model and used to generate a revised set of rankings (catchment scores). In addition as understanding improves, the weightings assigned to the criteria and sub-criteria in the hierarchical model can be adjusted, and criteria and sub-criteria added or removed.
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
7. REFERENCES Anonymous (2009) Expert Choice 11.5. Expert Choice Inc., Pittsburgh, PA, United States of America. ARC (2002) A System for Soil and Land Capability Classification for Agriculture in South Africa. Institute of Soil, Climate and Water, Agricultural Research Council, Pretoria. DEA (2009) List of threatened terrestrial ecosystems for South Africa (2009) [DRAFT] Notice 1477 of 2009, Government Gazette No 32689, 6 November 2009. Driver, A., Maze, K., Rouget, M., Lombard, A.T., Nel, J., Turpie, J.K., Cowling, R.M., Desmet, P., Goodman, P., Harris, J., Jonas Z., Reyers, B., Sink, K. and Strauss, T. (2005) National Spatial Biodiversity Assessment 2004: Priorities for biodiversity conservation in South Africa. Strelitzia 17, South African National Biodiversity Institute, Pretoria. DWAF (2005) Groundwater Resource Assessment. Phase II. Department of Water Affairs and Forestry, Pretoria. Dye, P. and Jarmain, C. (2004) Water use by black wattle (Acacia mearnsii): implications for the link between removal of invading trees and catchment streamflow response. South African Journal of Science 100, 40–44. Dye, P.J., Jarmain, C., Le Maitre, D.C., Everson, C.S., Gush, M. and Clulow, A. (2008) Modelling vegetation water use for general application in different categories of vegetation. WRC Report No. 1319/1/08, Water Research Commission, Pretoria. ENPAT (2001) Environmental Potential Atlas. Department of Environmental Affairs and Tourism, South Africa. Forsyth, G.G., Le Maitre, D.C. and van Wilgen, B.W. (2009) Prioritising quaternary catchments for invasive alien plant control within the Fynbos and Karoo biomes of the Western Cape province. CSIR Report CSIR/NRE/ECO/ER/2009/0094/B. Natural Resources and the Environment, CSIR, Stellenbosch. Henderson, L. (1998) Southern African Plant Invaders Atlas (SAPIA). Applied Plant Science 12, 31-32. Kotzé, I., Beukes, H., van den Berg, E. and Newby, T. (2010) National Invasive Alien Plant Survey. Report No. GW/A/2010/21, Agricultural Research Council – Institute for Soil, Climate and Water, Pretoria. Le Maitre, D.C. and Forsyth, G.G. (2010) Prioritising quaternary catchments for invasive alien plant control within the Savanna, Nama and Succulent Karoo biomes of the Northern Cape province. CSIR Report CSIR/NRE/ECO/ER/2010/0015/B. Natural Resources and the Environment, CSIR, Stellenbosch.
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Meininger, W. and Jarmain, C. (2009) Development of remote sensing tools for monitoring the hydrological benefits of the Working for Water Programme. Report prepared for the Working for Water Programme, Working for Water, Cape Town. Mgidi, T.N., Le Maitre, D.C., Schonegevel, L., Nel, J.L., Rouget, M. and Richardson, D.M. (2007) Alien plant invasions – incorporating emerging invaders in regional prioritization: a pragmatic approach for southern Africa. Journal of Environmental Management 84, 173-187. Middleton, B.J. and Bailey, A.K. (eds) (2008) Water Resources Of South Africa, 2005 Study (WR2005). Report TT 380/08, Water Research Commission, Pretoria. Mucina, L. and Rutherford, M.C. (2006) The vegetation of South Africa, Lesotho and Swaziland. Strelitzia. South African National Biodiversity Institute, Pretoria. Naudé, A.H., Badenhorst, W., Zietsman, H.L., van Huyssteen, E. and Maritz, J. (2007) Technical overview of the mesoframe methodology and South African Geospatial Analysis Platform. CSIR, Pretoria. (Report number CSIR/BE/PSS/IR/2007/0104/B). Nel, J.L., Roux, D.J., Maree, G., Kleynhans, C.J., Moolman, J., Reyers, B., Rouget, M. and Cowling, R.M. (2007) Rivers in peril inside and outside protected areas: a systematic approach to conservation assessment of river ecosystems. Diversity and Distributions 13, 341–352. Nel, J.L., Driver, A., Strydom, W., Maherry, A., Petersen, C., Roux, D.J., Nienaber, S., van Deventer, H., Smith-Adao, L.B. and Hill, L. (2011) Atlas of Freshwater Ecosystem Priority Areas in South Africa: Maps to support sustainable development of water resources. Atlas and accompanying data available from CSIR or WRC. Rouget, M., Richardson, D.M., Nel, J.L., Le Maitre, D.C., Egoh, B. and Mgidi, T. (2004) Mapping the potential ranges of major plant invaders in South Africa, Lesotho and Swaziland using climatic suitability. Diversity and Distributions 10, 475 – 484. Saaty, T.L. (1990) How to make a decision: The analytic hierarchy process. European Journal of Operational Research 48, 9-26. Scholes, R.J. (1998) The South African 1:250 000 maps of areas of homogenous grazing potential. Report ENV-P-C 98190, CSIR, Pretoria. Van den Berg, E.C., Plarre, C., van den Berg, H.M. and Thompson, M.W. (2008) The South African National Land Cover 2000. Agricultural Research Council (ARC) and Council for Scientific and Industrial Research (CSIR), Pretoria. Report No. GW/A/2008/86. van Wilgen, B.W., Forsyth, G.G. and Le Maitre, D.C. (2008) The prioritization of species and primary catchments for the purposes of guiding invasive alien plant control operations in the terrestrial biomes of South Africa. CSIR Report CSIR/NRE/ECO/ER/2008/0070/C. Natural Resources and the Environment, CSIR, Stellenbosch. van Wilgen, B.W., Le Maitre, D.C., Forsyth, G.G. and O’Farrell, P.J. (2010) The prioritization of terrestrial biomes for invasive alien plant control in South Africa. CSIR Report CSIR/NRE/ECO/ER/2010/0004/C. Natural Resources and the Environment, CSIR, Stellenbosch.
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WSAM (2003) Water situation assessment model, Version 3.002. Department of Water Affairs and Forestry (DWAF), Republic of South Africa.
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
APPENDIX 1: PRIORITY INVASIVE ALIEN PLANTS IN THE MOIST SAVANNA AND GRASSLAND BIOMES FOR THE FREE STATE PROVINCE The invasive alien plant taxa selected for prioritization in the Grasslands, Nama Karoo, Moist Savanna and Arid Savanna biomes (# indicate those species identified by van Wilgen, Forsyth and Le Maitre, (2008) as a threat but not regarded by the Free State experts as a threat; * denotes species regarded as problematic and added to the list during the workshop by the local experts). Grassland species Acacia mearnsii, dealbata and decurrens (Black, silver and green wattle) Arundo donax (Giant reed)# Cacti with effective bio-control agents Cacti without effective bio-control agents Campuloclinium macrocephalum (Pom-pom weed) Celtis sinesis (Netelbome)* Cestrum lavigatum (ink berry)* Chromolaena odorata (Triffid weed)# Cirsium vulgare (Scotch thistle)* Cotoneaster franchetii and pannosus ( and silver-leaf cotoneasters)# Datura stramonium (Common thorn apple)* Eucalyptus camaldulensis (Gum) Eucalyptus cinerea (Florist gum)# Eucalyptus sideroxylon (Red Ironbark) Ipomoea indica (Morning glory)# Pinus elliottii (Slash pine)# Pinus patula (Patula pine) Populus x canescens and alba (Grey and white poplars) Pyracantha angustifolia (Yellow firethorn) Robinia pseudoacacia (Black locust) Rosa rubiginosa (Wilderoos)* Rubus cuneifolius (American bramble) Salix babylonica (Weeping willow) Salix fragilis (Crack willow)# Solanum elaeagnifolium (Satan’s bush) Solanum mauritianum (Bugweed) Tamarix galica (French Tamarix)* Xanthium spinosum (Boetebos)* Xanthium strumarium (Kankerroos)*
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
Nama Karoo species Arundo donax (Giant reed)# Cacti with effective bio-control agents Cacti without effective bio-control agents Caesalpinia gilliesii (Bird-of-paradise bush)# Casuarina equisetifolia (Beef wood)# Eucalyptus camaldulensis (Red river gum) Pennisetum setaceum (Fountain grass)# Pinus halepensis (Aleppo pine)# Populus x canescens (Grey poplar) Prosopis x glandulosa (Mesquite) – All species Schinus molle (Pepper tree)# Solanum elaeagnifolium (Satan’s bush) Tamarix ramosissima (Pink tamarisk)# Xanthium spinosum (Boetebos) Moist Savanna species Acacia mearnsii (Black wattle)# Arundo donax (Giant reed)# Caesalpinia decapetala (Thorn)# Cereus jamacaru (Queen of the night)# Cestrum laevigatum (Inkberry) Chromolaena odorata (Triffid weed)# Eucalyptus camalendensis (Red river gum)* Jacaranda mimosifolia (Jacaranda)# Lantana camara (Lantana)# Melia azedarach (Persian lilac) Parthenium hysterophorus (Parthenium)# Pereskia aculeata (Barbados gooseberry)# Pinus spp. (elliottii and patula)# Populus wizelia (Plains poplar)* Populus x canescens (Grey poplar)* Psidium guajava (Guava)# Senna spp. (Peanut butter cassia and others) Arid Savanna species Arundo donax (Giant reed)# Cereus jamacaru (Queen of the night)# Melia azedarach (Persian lilac) Opuntia spp Populus x canescens (Grey poplar)# Prosopis x glandulosa (Mesquite) Robinia pseudoacacia (Black locust)# Schinus molle (Pepper tree)#
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
APPENDIX 2: AGENDA FOR FREE STATE REGION AGENDA: FREE STATE REGION RANKING THE IMPORTANCE OF CRITERIA TO USE IN PRIORITISING QUATERNARY CATCHMENTS TO CLEAR OF INVASIVE ALIEN PLANTS IN THE FREE STATE
Spruite Boardroom Working for Water: Bloemfontein Regional Office Corner Maitland and East Burger Streets Bloemfontein
Thursday 20th January 2011 1. 2. 3. 4. 5. 6.
Welcome (10h15) Introduction: Aims of workshop and AHP method (10h30) Results of previous prioritisation studies (10h45) Discuss current rankings of important invasive alien species in Free State (11h00) Tea (11h00 – 11h15) Agree on goal, criteria (objectives) and sub-criteria (sub-objectives) for prioritising quaternaries catchments in Free State (11h15) 7. Pairwise comparisons of criteria and sub-criteria (12h15) 8. Lunch (13h00 – 13h45) 9. Continuation of pairwise comparisons of criteria and sub-criteria (13h45) 10. Discussion of relevant and available datasets for Free State (15h00) 11. Workshop ends at approximately 16h00
Enquiries: Cedric Singo Tel: 051 405 9000 ext 2119 Cell: 082 907 9818 Email:
[email protected]
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Prioritising quaternary catchments for invasive alien plant control within the Working for Water Free State region
APPENDIX 3: PARTICIPANTS IN THE EXPERT WORKSHOP Participants in the workshop held in the Spruite Board Room, Department of Water Affairs’ Regional Office, corner of Maitland and East Burger Streets, Bloemfontein on 20th January 2011 to determine criteria and rank these to use in prioritising the clearing of invasive alien plants from quaternary catchments within the Free State province.
#
Organisation
Telephone
E-mail
Greg Forsyth
CSIR
021 888-2400
[email protected]
2
Cedric Singo
Working for Water
082 907-9818
[email protected]
3
Kefilwe Disipi
DAFF - LUSM
084 813-1811
[email protected]
4
Makolane Mofokeny
DAFF- Forestry
083 390-3094
[email protected]
5
Bornett Matoto
082 323-6134
[email protected]
6
Simaei Patrick
082 800-1750
[email protected]
7
Eliot Lithudzha
SANBI
051 436-3530
8
D.R. Moha
DAFF
082 803-0936
[email protected]
9
Z. Mokgalagadi
082 323-9301
[email protected]
1
Name
Working for Water
Working for Water
10
Peter Hawley
The River Trust
082 440-2374
[email protected]
11
Jan Richter
DOA FS
051 861-1124
[email protected]
12
Chris Smith
Landcare DoA FS
13
Neiukalo Thirsawanga
DWA
051 405-9000
[email protected]
14
Nokulunga Mahlangu
DWA
082 808-5632
[email protected]
15
Shamley Mogale
16
Paul Mazwi
DAFF – LUSM
051 409-2619
[email protected]
17
Izak Venter
FS DOA
051 861-1159
Izak@gwem,agric.za
18
Hanlio Klopper
19
Elize Pienaar
20 21 22
Thami Gugushe
[email protected]
Working for Water
[email protected]
Environmental Affairs
051 433-2012
[email protected]
Working for Water
082 415-6773
[email protected]
Malcom Procter
DAFF National
082 808-2735
[email protected]
Johan Zeelie
DAFF – LUSM
051 409-2624
[email protected]
DAFF
051 405-9000
[email protected]
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