INVERTEBRATE STUDY FOR PORTION 62 OF THE FARM WITPOORTJIE 177-IR, GAUTENG PROVINCE by V.C. VAN DER MERWE BSc Entomology, MSc Conservation Biology Commisioned by Envirogaurd December 2018 V.C. VAN DER MERWE EMAIL: [email protected] P.O.BOX 72 CELL: 074 166 0410 HAENERTSBURG 12 DECEMBER 2018 0730 LIMPOPO, SOUTH AFRICA Invertebrate Assessment – Ptn 62 Witpoortjie 1 To Envirogaurd INVERTEBRATE STUDY FOR PORTION 62 OF THE FARM WITPOORTJIE 177-IR, GAUTENG PROVINCE We have the pleasure in submitting herewith our report as requested and as per your correspondence and appointment dated 11th November 2018. This study has been carried out in accordance with the provisions of Regulations gazetted in the Government Notice No R1183 of 6/9/1997 for the Department of Nature Conservation, of Gauteng Province, and also DEAT (2005) Guideline 3: General Guide to the Environmental Impact Assessment Regulations, 2005, Integrated Environmental Management Guideline Series, Department of Environmental Affairs and Tourism (DEAT), Pretoria. The aim of this report was to provide the client with a description of potential status of Red Data Invertebrate species and habitat that could be potentially suitable for the presence of these species on Portion 62 of the Farm Witpoortjie 177-IR. A concerted effort was made to locate four invertebrate species of conservation concern, including three butterfly species (Lepidochrysops praeterita, Chrysoritis aureus and Aloeides dentatis) and one cetonid beetle (Ichnestoma stobbiai). These species were not observed during the survey. The vast majority of the site consists of open grasslands and old fields that has been heavily invaded by anthropogenic, pioneer and exotic plant species. These areas are totally transformed and no natural vegetation remains. Three seasonally inundated depressions on the eastern portion of the site constitute the only sensitive habitat in the survey area. Invertebrate Assessment – Ptn 62 Witpoortjie 2 CONTENTS EXECUTIVE SUMMARY…………………………………………… 2 INTRODUCTION…………………………………………………….. 4 STUDY AREA……………………………………………………….. 6 MATERIALS & METHODS………………………………………… 12 RESULTS…………………………………………………………….. 14 DISCUSSION………………………………………………...………. 20 RECOMMENDATIONS…………………………………………….. 23 REFERENCES………………………………………………………. 26 Invertebrate Assessment – Ptn 62 Witpoortjie 3 INTRODUCTION Biodiversity is the variability among living organisms on earth, including the variability within and between species and within and between ecosystems. The biodiversity of Gauteng is under constant threat from human settlement and societal development. Natural land is degraded and transformed by the rapid expansion of human settlements, such as residential areas, mines, manufacturing plants, transport and agriculture, that have an ever-increasing demand for space. The loss, fragmentation and degradation of natural habitat through urbanisation and an increase in human population numbers, represent the greatest threats to rare and endangered invertebrate species in Gauteng. Sustainable development is an evolving concept, which is continually being redefined and reinterpreted and should form the basis of the planning processes of new developments. Reducing the burden of environmental impacts is necessary if development is to become sustainable. The process of planning new developments should be based on scientific, ecological principles and used as a planning tool to promote sustainable development by integrating environmental considerations into a wide range of proposed actions. Development planning must be intended to ensure that development proposals do not undermine critical resource and ecological functions, by improving the way these environmental resources are utilised, or the well being, lifestyle and livelihood of the communities and peoples who depend on them. Invertebrates dominate terrestrial and freshwater ecosystems, with insects being the most speciose class, comprising more than 75% of all known species in the Animal Kingdom. Insects and arachnids form part of the diverse and essential natural processes that sustain biological systems. The insect-plant interaction is the most common biotic interaction on Earth, and indeed, our present ecosystems would not function without these invertebrates. The worldwide Red List of Threatened Species (http://www.redlist.org/info/tables/table1) contains approximately 560 insects. This is a meagre 7% of the faunal list, which when one consider that insects make up over 70% of the worlds fauna, is tremendously negatively biased. In a study carried out by Black and Vaughn (2003), it was noted that of the world’s insects, very few groups have been assessed on a worldwide scale. Approximately 10% of Swallowtail butterflies, for example, are considered globally threatened. Based on a mathematical model, McKinney (2003), predicted that 10% of all butterflies were threatened contrasting to the 1% currently listed. At National levels, figures between 10% and 34% are given for the number of threatened indigenous insect species, suggesting that the overall number of threatened insects could be in excess of 100, 000. Globally countries such as Australia, France, Spain, the United Invertebrate Assessment – Ptn 62 Witpoortjie 4 States and South Africa have among the highest numbers of threatened invertebrates. This is however, more a reflection of the effort made by these countries to assess their biodiversity and hence distinguish those that are threatened rather than a true overall indication. Insects have an enormous functional value because of the numerous individuals and the great intra- and interspecific variety. The ecological importance of this great variety of insects makes them valuable to assess disturbances or environmental impacts. A sound knowledge of arthropods is crucial to the conservation and management of ecosystems because a skewed focus only on the larger organisms will misrepresent ecosystem dynamics. The lack of human appreciation of the importance of invertebrates and their general disregard and dislike, coupled to the fact that only about 7-10% of insects are scientifically described, must be overcome to realistically conserve biodiversity. Photograph 1. The majority of the site has been subject to heavy overgrazing. Invertebrate Assessment – Ptn 62 Witpoortjie 5 STUDY AREA Figure 1. Locality map of the proposed Witpoortjie site. Invertebrate Assessment – Ptn 62 Witpoortjie 6 Photograph 2. The Witpoortjie site is dominated by Tsakane Clay Grassland in various stages of transformation and degradation. Situated within the lower-lying areas as well as shallow depressions are seasonally inundated pans. The Witpoortjie site is situated within the East Rand of Gauteng. The site is bordered to the west by the M43 (Sailfin), R554 and Van Dyk Dam to the north and open grasslands and Dalpark to the east and degraded open grasslands to the south (see Figure 1 above). Major bulk pipelines and railway track occur on the southern boundary of the site. Invertebrate Assessment – Ptn 62 Witpoortjie 7 Figure 2. An elevation profile of the site. The site has a gentle sloping topography from the north towards the east with an average slope of 1.3%. The major topographical features are the artificially created mine dumps (old slimes dam) on the northern portion of the site. Vegetation composition in the area consists of Mesic Highveld Grasslands in various stages of transformation and degradation falling within the Tsakane Clay Grassland (Gm 9) vegetation unit (Mucina & Rutherford 2006; see Figure 4 below). The majority of grasslands have been historically transformed through agricultural activities as well as high-density residential developments and associated high levels of anthropogenic disturbances including extensive illegal dumping activities, littering, frequent fires (burning of waste) and harvesting of traditional medicinal plants. The grasslands to the south of the site comprise of degraded grassland with limited herb and forb diversity. Patches of primary Themeda triandra grassland were observed on the western, southern as well as central portions of the site. Several patches of the hydrophilic Imperata cylindrica was observed within a mosaic in areas with elevated soil moisture throughout the site. One general habitat sensitivity scans was carried out mainly during daylight hours (9h00- 14h00) on the 22nd of November 2018. The majority of the surveys were conducted on existing roads, livestock pathways as well as off-road vehicle and quad bike tracks within the grasslands. Due to the large size of the site little time was spent surveying the old slimes dam and mine dumps or degraded habitats Invertebrate Assessment – Ptn 62 Witpoortjie 8 Figure 3. Vegetation map of the Witpoortjie site situated within Tsakane Clay Grassland (Gm9) (adapted from Mucina et al. 2006). Invertebrate Assessment – Ptn 62 Witpoortjie 9 Vegetation type Mesic Highveld Grassland is found mainly in the eastern, precipitation-rich regions of the Highveld, extending as far as the Northern Escarpment. These are predominantly ‘sour’ grasslands and are dominated primarily by andropogonoid grasses. The different grassland units are distinguished on the basis of geology and other substrate properties, as well as elevation, topography and rainfall. The vegetation of the site falls within the Tsakane Clay Grassland (Gm 8) vegetation unit (Mucina & Rutherford 2006). The vegetation on the site comprised cool Highveld Grassland in various stages of transformation and degradation. Patches of Themeda traiandra