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National Botanical Gardens: South Africa’s urban conservation refuges

Volume 5 Number 2 - July 2008

Christopher Willis & Augustine Morkel

Introduction

South Africa’s National Botanical Gardens (NBGs) mean different things to different people. Traditionally, botanical gardens, as their name implies, have been viewed primarily through a botanical filter. Indeed, Botanic Gardens Conservation International (BGCI) has defined botanical gardens as ‘institutions holding documented collections of living plants for the purposes of scientific research, conservation, display and education’. There is, however, much more to botanical gardens, particularly in South Africa, where all NBGs are classified as ‘conservation gardens’, each including an area of natural indigenous vegetation (with its associated wealth of biodiversity and biological interactions) as well as cultivated collections.

Up until 2007, SANBI managed eight urban-based NBGs mostly located in large towns or cities and bordered in part by urban and peri-urban developments that include roads, townhouse complexes and individual households as well as protected areas such as national parks (Kirstenbosch adjacent to the Table Mountain National Park) and nature reserves (Harold Porter NBG adjacent to the Kogelberg Nature Reserve). In 2008, when the new garden in Nieuwoudtville was launched, SANBI established its first Nature or Wild Garden, with the aim of conserving a network of sites containing representative portions of Indigenous vegetation unique to the Bokkeveld Plateau. This Garden faces its own unique challenges in that it is located in a predominantly agricultural area where sheep, wheat and rooibos tea are the main farming products.

South Africa’s nine NBGs are currently spread across six provinces, and include over 7,000 ha of natural vegetation, ranging from savanna bushveld, highveld grassland to subtropical forest, mountain, coastal and renosterveld fynbos to arid succulent karroid vegetation. Based on a preliminary review of living collections in South Africa’s NBGs, it has been estimated that the gardens together house some 8,500 indigenous plant species, 43% of South Africa’s 19,581 indigenous species. The number of indigenous plant taxa per garden ranges between 350 in the Free State NBG to 5,506 in Kirstenbosch NBG (28% of South Africa’s indigenous species). SANBI’s gardens attract over 1.25 million visitors per year and, while the visitors to most gardens are largely local, Kirstenbosch in particular receives a significant portion (21%) of visitors as part of organized tour groups, both national and international.

SANBI: the biodiversity challenge

The formation of the South African National Biodiversity Institute (SANBI) in September 2004 through the proclamation of the National Environmental Management: Biodiversity Act (NEMBA) provided the ideal opportunity to showcase the total biological diversity held within South Africa’s NBGs. However, since Kirstenbosch was established in 1913, the organisation’s main focus has been on studying, documenting and conserving South Africa’s indigenous plants. There are therefore many gaps in our knowledge and understanding of the faunal diversity conserved in our gardens. While in most cases there is a fairly comprehensive understanding of the avian diversity in the NBGs, our knowledge of the lesser known, and very often less visible, groups, such as insects, reptiles, amphibians and even mammals is still very restricted. Clearly, there are many opportunities for individuals to further study and document the faunal diversity associated with South Africa’s NBGs.

Interpretation and courses

Although our knowledge of the gardens’ faunal diversity is still at an embryonic stage, South Africa’s NBGs have, for many years, been describing the interactions and dependencies between plants, people and animals through interpretive signage displayed in the gardens. This has been extended to general visitors through guided tours and to learners through formal educational programmes presented in the gardens. Several gardens offer weekend talks and specialised natural history courses, and visitors are encouraged to make use of the opportunities that are provided to learn more about biological diversity present in and outside our NBGs.

Surveys and monitoring

Most of the available information on the biodiversity conserved in South Africa’s NBGs has come from observations and ad hoc surveys completed by university staff and students, museums, and natural history societies and clubs. In recent years, natural history societies, museums and universities have been encouraged to monitor and survey the biodiversity within SANBI’s conservation gardens. Faunal groups surveyed have included birds, mammals, spiders, scorpions, bats as well as a range of insect groups (from dragonflies and damselflies to butterflies). In the Walter Sisulu NBG, where a world-renowned resident pair of Verreaux’s (Black) Eagles nests on the cliffs of the Witpoortjie Waterfall on the perennial Crocodile River, the breeding behaviour and movements of the eagles are regularly monitored by volunteers attached to the Black Eagle Project Roodekrans, a non-profit organisation dedicated to ensuring their survival Biannual biomonitoring of the Crocodile River that runs through the Walter Sisulu NBG has been conducted over the past few years. Results from surveys conducted have shown that the quality of the water improves as it flows though the Walter Sisulu NBG, with the Garden having a positive effect on the biological integrity of the river reach under SANBI’s management. Some 21 family representatives of aquatic macroinvertebrate taxa were recorded in the section of river that flows through the Garden. The Kitso-Ecocentre at the entrance of the Garden has an interesting live display of some of South Africa’s indigenous fish. Natural history courses on a range of biodiversity topics have been arranged and hosted by several gardens and have proven very popular amongst members of the public.

South Africa’s NBGs house an impressive diversity of plants and animals, and it is only through regular inventory and monitoring of biodiversity and habitats in the gardens that we can evaluate the effectiveness of management interventions. Probably the most challenging part of managing NBGs is balancing human values and needs with ecosystem processes. The value of collaboration and partnerships in the management of South Africa’s NBGs cannot be underestimated, and if we are to be successful in our management of the biodiversity within our gardens, there has to be close co-operation, facilitated by Garden Curators and their management teams, with local and provincial conservation agencies, universities, museums, natural history societies and volunteers. By sharing resources between agencies through partnerships and collaborative projects, funds and resources can be leveraged to achieve mutual conservation objectives.

Biodiversity havens

SANBI’s NBGs are home to a range of threatened and endemic fauna, from the endemic and Critically Endangered Table Mountain Ghost Frog, found only along forest streams on Table Mountain above Kirstenbosch, to the Marico Barb, a threatened indigenous fish found as recently as November 2007 in the Crocodile River that flows through the Walter Sisulu NBG in Roodepoort/ Mogale City. South Africa’s NBGs in general serve an important role as refuges for many invertebrate taxa. A recent study conducted by the Department of Conservation Ecology and Entomology of Stellenbosch University has indicated that young forests and Kirstenbosch’s cultivated gardens show the highest ground-living and flying invertebrate diversity on Table Mountain.

Studies in the KwaZulu-Natal NBG, where 120 butterfly species have been recorded, have shown that the KwaZulu-Natal NBG is important not only for introducing butterfly conservation to the general public, but also acts as a valuable refuge for many butterfly species in the urbanised area of Pietermaritzburg. Surveys completed in the Garden by staff and students of the University of KwaZulu-Natal culminated in a dedicated Damselfly and Dragonfly Trail being developed inside the Garden in 2000. Repeated surveys conducted along the trail over a three-year period have indicated that from a list of 36 species (21 dragonflies and 15 damselflies) there are 24 ‘core resident species’ that can be seen along the trail in the various habitats from January to May. It is possible therefore, on occasion, to account for all 24 during a single visit during this peak period. Academics from the University of KwaZulu-Natal have stated that ‘botanical gardens are inherently valuable for drawing public attention to invertebrates, especially dragonflies which, like butterflies, have iconic value….to provide optimal conditions for a wide range of observable species, it is essential to maintain the natural heterogeneity of vegetation along reservoir and stream margins….removal of marginal vegetation for aesthetics or a sense of tidiness, can reduce local species diversity and abundance.’

The banning of dogs from several NBGs has resulted in a significant increase in the number and visibility of various mammals in the gardens concerned. This policy will ultimately be extended to all NBGs as the conservation role of South Africa’s NBGs in rapidly expanding urban centres becomes more important and valuable. One of the advantages of SANBI’s gardens is that not all the gardens are functionally isolated but lie adjacent to natural habitats of varying sizes, providing connectivity between the gardens and their surrounding environment as well as valuable biodiversity corridors and landscape linkages for the movement of animals into and out of the gardens.

Management challenges

NBGs are managed with the aim of maximising their biodiversity display, conservation, education and research functions. While the natural areas of the gardens perform important roles as refuges for many different animals and plant species, these areas, with the exception of the Hantam NBG in Nieuwoudtville (which comprises 6,200 ha and is mainly a natural or wild garden), are relatively small compared with many other nature reserves and national parks. There are also, in most cases, no large natural predators (e.g. large cats, pythons, raptors) to control populations of some species. This requires management intervention to keep some kind of balance. For example, the population of Rock Hyraxes in the Pretoria NBG has grown significantly over the past few years because of the absence of their natural predators, Verreaux’s Eagles, from the eastern suburbs of Pretoria. In collaboration with Tshwane Nature Conservation, a relocation programme was initiated by which hyraxes were trapped in cages and then released in other nature reserves in and around Pretoria. Since the project started, 82 hyraxes have been captured and relocated to the Groenkloof and Wonderboom Nature Reserves. Other challenges include the introduction of feral animals (such as cats and dogs) or the introduction of rabbits by some members of the public who may unfortunately mistakenly perceive NBGs as places of refuge for their unwanted pets and associated litters. Domination by certain naturalised birds, such as the Common (Indian) Myna, can also cause disturbance to the natural populations of birds in certain gardens; they also compete with indigenous birds and mammals for nesting cavities. Common Mynas have now become a pest in many urban areas in South Africa, particularly in Gauteng and KwaZulu-Natal. They are now considered by the World Conservation Union (IUCN) as one of the world’s 100 worst invasive species and do not warrant protection. Mynas compete aggressively with many indigenous species and tend to replace them in areas where Myna populations are well established. Other alien species that are a potential threat to South Africa because of their aggression towards indigenous species include the House Crow and the Common (European) Starling. Maintaining a cultivated garden in association with wildlife can also be frustrating, particularly when certain mammals take a preference to plants that horticulturists are attempting to cultivate and display for visitors. This includes the activities of cane rats, moles, baboons and porcupines in several gardens, as well as the effect of alien invasive grey squirrels on strelitzias cultivated for their seed in Kirstenbosch.

Biodiversity management systems

With the promulgation of the NEMBA in 2004, SANBI has renewed its focus on the conservation of all forms of life in its NBGs, with the ultimate aim that biodiversity and ecological processes within the boundaries of the Gardens will be conserved for both present and future generations. The effective management of the biodiversity housed within South Africa’s NBGs requires the development of biodiversity information management systems that include databases, threatened status categorisation, annual indicator surveys, preparation of GIS maps and significant research projects. A need exists to consolidate and standardise a dynamic biodiversity information system, linked to horticultural databases, for South Africa’s NBGs. There is also a need to be able to document and evaluate the conservation effectiveness of garden management practices, using indicators such as land alteration, edge effect, riparian buffers, spatial configuration and connectivity, effectiveness of land management for ecological conservation and effectiveness of restoration efforts.

Conclusion

SANBI’s ultimate aim is to conserve and celebrate biodiversity and educate members of the public about its value and importance, both inside and outside the boundaries of South Africa’s NBGs. The underlying assumption is that people with more exposure to nature are more interested in conserving it. It has been shown that direct experience with the natural world, especially during childhood, appears to be the most important source of environmental sensitivity. As human populations shift to cities, people will experience nature primarily through contact with urban nature. If it is true that conservation will increasingly depend on the ability of people in cities to maintain a connection with nature, then South Africa’s NBGs as urban refuges for biodiversity, and places that allow people to connect with natural habitats and ecosystems, will become increasingly more valuable for future generations.

References

  • Honig, M., 2000. Making your garden come alive!—Environmental interpretation in botanical gardens. Southern African Botanical Diversity Network Report No. 9. SABONET, Pretoria, South Africa. 92 pp.
  • Willis, C.K., 2005. National Botanical Gardens: embassies of South Africa’s biodiversity and culture. BGjournal 2(2): 9-12.
  • Willis, C.K., 2006. SANBI: Institutional response to implementing the International Agenda. BGjournal 3(1): 11-13.
  • Willis, C.K. & Huntley, B.J., 2004. Establishing National Botanical Gardens in South Africa. SABONET News 9(1): 5-13.
  • Willis, C.K. & Morkel, A.T., 2007. National Botanical Gardens: havens of biodiversity. Supplement to: Veld & Flora 93(4). Published by Botanical Society of South Africa and SANBI.

Christopher Willis, Chief Director: ConservationGardens & Tourism,
SANBI, Private Bag X101, Pretoria 0001, South Africa.
Tel.: +27 (0)12 843 5200
E-mail: willis@sanbi.org
Internet: www.sanbi.org
 

Augustine Morkel, Estate Manager, Kirstenbosch National Botanical Garden,
Private Bag X7, Claremont 7735, South Africa.
Tel.: +27 (0)21 799 8761
E-mail: amorkel@sanbi.org