Comparison of Extent and Transformation of South Africa's
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View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by South East Academic Libraries System (SEALS) Research in Action South African Journal of Science 97, May/June 2001 179 remote sensing applications in South Comparison of extent and Africa. This is a hierarchical framework designed to suit South African conditions, transformation of South Africa’s and incorporates known land-cover types that can be identified in a consistent woodland biome from two national and repetitive manner from high- resolution satellite imagery such as Land- databases sat TM and SPOT.The ‘natural’vegetation classes are based on broad, structural M.W. Thompsona*, E.R. Vinka, D.H.K. Fairbanksb,c, A. Ballancea types only, and are not intended to be and C.M. Shackletona,d equivalent to a floristic or ecological vege- tation classification. It is important to understand that a HE RECENT COMPLETION OF THE SOUTH Fairbanks et al.5 combination of both the NLC database’s TAfrican National Land-Cover Database This paper compares the distribution ‘Woodland’ and ‘Thicket, Bushland, and the Vegetation Map of South Africa, and location of woodland and bushveld- Bush-Clump & Tall Fynbos’ land-cover Swaziland and Lesotho, allows for the first type vegetation categories defined within classes were used in the comparison with time a comparison to be made on a national scale between the current and potential the NLC data, and the equivalent the DEAT defined ‘Savanna Biome’. The distribution of ‘natural’ vegetation resources. ‘Savanna Biome’ class defined within the inclusion of the NLC’s ‘Thicket, Bushland This article compares the distribution and DEAT’s ‘VegetationMap’ data. Significant (etc.)’ class was seen as a necessity, since location of woodland-type vegetation catego- boundary discrepancies are reported be- this category also included a significant ries defined within the National Land-Cover tween the two data sets in terms of the component* of the traditional ‘bushveld’ data and the equivalent ‘Savanna-thicket overall woodland/savanna extent. This is regions in northern and eastern South Biomes’ class defined within the Vegetation not (nor was it ever intended to be), a Africa, on the basis of structural appear- Map data. Significant differences were found, measure of inherent mapping accuracies, ance.12 both in terms of the total areal extent, as well as the actual spatial distribution of these two but rather an illustration of boundary Unfortunately, such an approach does data sets. These differences are a measure of delineation distinctions that are a result of not allow a clear separation between true the inherent mapping accuracies of each different raw data sources, mapping thicket (as in the ‘Thicket Biome’), and tall source, but rather an illustration of boundary objectives and final information classes, fynbos communities (as in the ‘Fynbos delineation distinctions that are a result of that must be noted when comparing two Biome’), from the true bushland-type different data sources, mapping objectives essentially similar data sets. vegetation (such as occurs in the ‘Wood- and information classes, that must be noted The results presented are based on a land Biome’), since no separation was when comparing two essentially similar comparison of two specific data sets and made at this sub-class level within the information sets. the characterization of the various vege- original ‘Thicket, Bushland, Bush-Clump tation types contained within them. No & Tall Fynbos’ NLC-defined land-cover Background class. This will have resulted in some un- Large-area land cover maps are needed inference is made, or intended, as to the avoidable overlap between the extent of in many research and management activ- actual validity of these data sets, since, as in the case of the biomes, it is acknowl- NLC-defined Woodland and the ities, concerned with global change1, edged that the Thicket Biome is not uni- DEAT-defined Thicket and Fynbos biodiversity and conservation2,and versally recognized as being separate biomes, especially in the southern and biogeography3. These thematic maps are, 10 Eastern Cape regions. The NLC Forest by design, highly generalized abstrac- from the Savanna Biome. class (equivalent to the DEAT-defined tions of reality, in terms of spatial resolu- ‘Forest Biome’) was excluded from all cal- tion, boundary-line sinuosity, and classifi- Description of primary data culations. Full class definitions for these cation detail. The recent completion of The NLC database is intended to pro- NLC vegetation classes are provided in both the South African National Land- vide national, baseline information on 5 Table 1. Cover Database (NLC)46 and the Depart- land-cover and mappable land-use. The The DEAT’s ‘Vegetation Map’ (and ac- ment of Environment Affairs and Tour- primary objective of the project was to companying booklet) was developed ism’s (DEAT) ‘Vegetation Map of South produce a standardized land-cover data- with the aim of producing a revised vege- Africa, Swaziland and Lesotho’7,8 allows base for all of South Africa, Swaziland and tation map of South Africa, based on vege- for a timely comparison to be made on a Lesotho. The product is designed for tation structure and species composition,8 national scale between the current and 1:250 000 scale mapping applications which provided a broad overview of the potential distribution of ‘natural’ vegeta- (25 ha minimum mapping unit). It was region’s natural plant resources suitable tion resources. This type of exercise was derived (using manual photo-interpreta- for educators and planners.7 The bound- last conducted by Mall and Bossi9 for the tion techniques) from a new series of aries and vegetation types within this Fynbos Biome, with a re-interpretation by 1:250 000 scale geo-rectified ‘SpaceMaps’ (from the CSIR’s Satellite Applications map were delineated manually at work- aEnvironmentek, CSIR, P.O. Box 395, Pretoria, 0001 Centre, 1996), based on seasonally stan- shops by teams of botanists and from a South Africa. dardized, single date Landsat Thematic number of sources, such as geological, bConservation Planning Unit, Department of Zoology and pedological, climatological, remote sens- Entomology, University of Pretoria, Pretoria, 0002 South Mapper (TM) satellite imagery captured Africa. principally during the period 1994–95. cPresently with Percy FitzPatrick Institute, University of Cape Town,Private Bag, Rondebosch, 7701 South Africa. The legend used within the land-cover *9.4% (725 018 ha) of the Fynbos Biome and 40.48% dEnvironmental Science Programme, Rhodes University, database is based on the classification (1 681 753 ha) of the Thicket Biome were classified as Grahamstown, 6140 South Africa. scheme defined within the standard ‘Thicket, Bushland, Bush-Clump & Tall Fynbos’ in the NLC database,5 compared to 43.04% (18 356 631 ha) within the *Author for correspondence. 11 E-mail: [email protected]. framework defined by Thompson for Savanna Biome. 180 South African Journal of Science 97, May/June 2001 Research in Action Table 1. South African National Land-Cover database class definitions. Class name Definition Forest All wooded areas with tree canopy cover greater then 70%, where the canopy is composed of mainly self-supporting, single-stemmed, woody plants >5 m in height. A multi-strata community, with interlocking canopies, composed of canopy, sub-canopy, shrub and herb layers. Composed of mainly indigenous tree species, growing under natural or semi-natural conditions (although it may include some localized areas of self-seeded exotic species). Excludes planted forests (and woodlots). Typically associated with the Forest biome in South Africa. Woodland All wooded areas with tree canopy cover of 9–70%, where the canopy is composed of mainly self-supporting, single-stemmed, woody plants >5 m in height. Essentially a broad open-closed canopy woodland community, typically consisting of a single tree canopy layer and a herb (grass) layer. Composed of mainly indigenous tree species, growing under natural or semi-natural conditions (although it may include some localized areas of self-seeded exotic species). Excludes planted forests (and woodlots). Typically associated with the Savanna biome in South Africa. Thicket, Bushland, Bushclumps and Tall Fynbos Communities typically composed of tall, woody, self-supporting, single and/or multi-stemmed plants (branching at or near the ground), with, in most cases, no clearly definable structure. Total canopy cover >9%, with canopy height of 2–5 m. Essentially indigenous species, growing under natural or semi-natural conditions (although it may include some localized areas of self-seeded exotic species, especially along riparian zones). Typical examples are Valley Bushveld, Mopane bush and many areas traditionally described as ‘bushveld’. Dense bush encroachment areas would be included in this category. Degraded class sub-division Permanent or seasonal, anthropogenic areas of very low vegetation cover (i.e. removal of tree, bush and/or herbaceous cover) compared to the surrounding natural vegetation cover. These classes are sub-divisions of each Level I vegetation classes, i.e. Degraded-Woodland, in order to allow reconstruction of full class-type extent. Typically associated with subsistence level farming and rural population centres, where overgrazing of livestock and/or wood-resource removal has been excessive. Often associated with severe soil erosion. Characterized on satellite imagery by significantly higher overall reflectance levels (i.e. whiter appearance) and lower NDVI values (compared to the surrounding vegetation). ing (e.g. only for ‘Fynbos’ and ‘Thicket’ types that would have potentially containing 25 different vegetation types, biomes), and other relevant cartographic occurred today, were it not for the major which are listed in Table 2. data. anthropogenic transformations such as A comparison of the two data sets The DEAT map differs from both the cultivation, afforestation, urban spread provides an opportunity to assess, at a NLC data and for that matter Acocks’s and dams that have altered the land- national level, the differences in distribu- Veld Types,13 since the vegetation units scape.