The Blaauwberg Sand Fynbos large-scale ecological restoration project

September 17, 2019January 15, 2021 admin active restoration, Blaauwberg, City of Cape Town, Ecological restoration, invasion, seed ecology, Stellenbosch University, treatment

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Description

This ecological restoration project began in 2012 as a collaboration among City of Cape Town, Stellenbosch University and the Millenium Seed Bank programme. The project has both research and operational management components, fostering a co-learning approach that is designed to improve the outcomes of ecological restoration interventions. The project also explores ways to scale-up restoration and improve efficiency. This is important as restored ecosystems will improve the conservation of biodiversity, delivery of ecosystem services, adaptation to climate change and potentially contribute to climate change mitigation and the social value of nature reserves.

The current phase of the ecological restoration project continues the City of Cape Town and Stellenbosch University collaboration and is funded by the Hans Hoheisen Trust for three years from 2019-2021. There are two components: The first is an operational component, administered through the Wilderness Foundation, to clear 24 ha of Acacia saligna from highly degraded Cape Flats Sand Fynbos, and collect, sort and pre-treat Fynbos seeds for sowing across the alien-cleared landscape. The second component comprises two research projects and is administered through Stellenbosch University. The PhD study will examine restoration techniques that avoid the immediate use of fire (which results in expensive acacia follow-up) and the MSc study will explore applied nucleation as a method to scale-up restoration.

A: Foreground – Friends Patch at Blauwberg – it is missing the Proteaceae overstory component (Photo: Tony Rebelo & Pat Holmes)

Photo 1A & B. Uninvaded reference sites – Cape Flats Sand Fynbos has high biodiversity and high endemism and these lowland sites are highly transformed (invasion) and fragmented.

**Photo 2**. Alien clearance on site commenced in September 2012 and the first-stage experimental area of 76ha was cleared by March 2013 (Photo: City of Cape Town)

**Photo 3.** By 2013, a quarter of the area had been cleared using two alien treatments with variants in fuel load and trialled in 1ha-sized plots; namely (pictured here) Fell & Burn in early autumn with 1) high and 2) low fuel load (Photo: City of Cape Town).

**Photo 4.** The second alien clearing treatment was Fell & Stack, with 3) high and 4) low fuel loads. At these sites (Photo 2 &3), we (Stellenbosch University & City of Cape Town) investigated optimal (passive and active) restoration treatments, seed ecology, small mammal ecology and soil microbial ecology in relation to the restoration treatments conducted. (Photo: City of Cape Town).

Photos 5 A & B. Fell & Burn, Active Restoration (Seeded) – 2013 (Photo: Stuart Hall) and 2019 (Photo: Pat Holmes). In this treatment, massive recruitment response from acacia post-fire swamps indigenous recruitment; aliens dominate seed banks; fire beneficial where remnant patches survived (higher restoration potential areas). Follow-up manual acacia clearing is most effective but too expensive to be viable large-scale. Herbicide foliar spray kills some indigenous species, but is less costly for dense acacia recruitment. Herbicide must be applied to cut stems to prevent coppicing in A. saligna but must be done carefully to minimize collateral damage. Sowing back of serotinous Proteaceae post-fire greatly improves vegetation structure in cases where some fynbos soil-stored seed banks persist. In dense acacia-invaded fynbos, post-fire sowing of a comprehensive fynbos mix is required to improve fynbos recruitment yet guild structure & community composition do not approach reference site conditions after a single sowing (Hall et al. 2017; Hall 2018).

Photos 6 A & B. Fell & Stack, Passive Restoration in low restoration potential area – 2014 (Photo: Stuart Hall) and 2019 (Photo: Pat Holmes). Fell & stack treatment sufficient if >10% cover structurally intact fynbos is present, but very low recruitment following alien removal in closed stands with <10% fynbos cover. Legacy effects of Acacia results in medium-term altered soil chemistry and potential to promote secondary invasions by herbaceous species (Krupek et al. 2016; Hall 2018; Nsikani et al. 2019)

**Photo 7.** From 2019, a new group of C.I.B affiliated students has started to work on site, including Duduzile Ngwenya (PhD, SU: How to scale up active restoration: Circumventing natural processes as a management tool in Sand Fynbos), Tevan Lehman (MSc, SU: Exploring the concept of applied nucleation as a restoration tool in previously-invaded Cape Flats Sand Fynbos in the Blaauwberg NR) and Aneesa du Plessis (MSc, CPUT: Do pollinators return after invasive alien plant clearing and restoration in Cape Fynbos?)

Key references

Hall, S., Newton, R., Rebelo, P., Gaertner, M., Esler, K.J. (2017) Heat and smoke pre‐treatment of seeds to improve restoration of an endangered Mediterranean climate vegetation type. Austral Ecology, 42(3): 354-366.

Hall, S. (2018) Restoration potential of alien-invaded Lowland Fynbos. PhD Dissertation, Stellenbosch University. Supervisor: Prof. K.J. Esler; Co-supervisors: Prof Patricia M. Holmes; Dr M. Gaertner. 143p.

Holmes PM, Esler KJ, Gaertner M, Geerts S, Hall SA, Nsikani MM, Richardson DM, Ruwanza S (2019) Biological invasions and ecological restoration in South Africa In: van Wilgen BW, Measey GJ, Richardson DM, Wilson JR, Zengeya, T (eds) Biological invasions in South Africa. Springer, Berlin [Book In Press].

Krupek, A., Gaertner, M., Holmes, P.M., Esler, K.J. (2016) Assessment of post-burn removal methods for Acacia saligna in Cape Flats Sand Fynbos, with consideration of indigenous plant recovery. South African Journal of Botany 105:211-217.

Nsikani, M.M., Gaertner, M., Kritzinger-Klopper, S., Ngubane, N.P., Esler, K.J. (2019) Secondary invasion after clearing invasive Acacia saligna in the South African Fynbos. South African Journal of Botany 125: 280-289.

Partners

The City of Cape Town, Key contact: Dr Charmaine Oxtoby; Biodiversity Management Branch I Environmental Management Department I Spatial Planning and Environment Directorate; ch**************@ca******.za

Stellenbosch University, Centre for Invasion Biology and Dept. Conservation Ecology & Entomology. Key Contacts: Professor Karen J Esler (ConsEnt; kj*@su*.za ), Professor Pat Holmes (ConsEnt & C.I.B, ho***************@gm***.com ).

Funders

Centre for Invasion Biology (2012 – Ongoing)
City of Cape Town (Operational and in-kind, 2012 – ongoing)
Millenium Seed Bank programme (2012 – 2015)
Hans Hoheisen Trust (2019-2021)

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