ReStory Narrator: Georgina van Biljon
The Berg and Breede Riparian Rehabilitation Programme (est. 2013) is one of the largest active riparian rehabilitation projects in South Africa. Initiated by the Department of Environmental Affairs and Development Planning, the project has planted approximately 2.16 million plants since its inception within an area of 18 ha. The primary aims of this project is to improve ecological functioning of the river, to create jobs (through EPWP) and to buffer the effects of climate change (flooding). The programme has involved over 30 landowners over the years, as key partners in their endeavours and Intaba Environmental Services has been one of the main service providers in this programme.
What is ecological infrastructure (natural capital) in riparian ecosystems?
Ecological Infrastructure refers to the goods and services that the environment provides to us (for free). By way of example, by planting and establishing palmiet (Prionium serratum) in the wet zone of a river, the speed of the river is reduced, decreasing the erosive ability of the water during flooding. It also helps to filter and clean the water due to its dense, mesh-like structure of old leaves that trap sediments (Rebelo et al. 2019). The amount of water lost through A-Pan evaporation (from the surface of the water) is more than what is lost through transpiration of palmiet (Rebelo et al. 2020).
There are multiple benefits associated with establishing the appropriate indigenous plants along riverbanks. Increasing and investing in a biodiverse landscape may act as a buffer against climate change and help to counteract impacts of extreme weather conditions like flooding. In other words, increasing biodiversity also increases the system’s ability to absorb and adapt to stresses. Other benefits of rehabilitation are habitat creation for pollinators, supporting fruit production in adjacent agricultural landscapes. Likewise, an increase in predatory insects that can take refuge in these biodiverse rehabilitated areas can act as natural pest control against aphids and other agricultural pests. Soil micro-organisms (like Collembola) thrive in healthy ecosystems and boost soil health. Restored riparian zones act as corridors for the movement of species across a landscape. These interconnections across landscapes also strengthens ecosystem resilience.
So how are riparian zones rehabilitated?
Firstly, contact a rehabilitation specialist to assist in devising a tailor-made plan according to the site conditions. Riparian zones are highly dynamic, and you need to have holistic understanding of geomorphology, hydrology, botany and horticulture in order to restore it. Attempting to do it yourself may seem like a less expensive option but can lead to some regrettable issues and ultimately end up costing considerably more than professional advice upfront. Remember, experts have had years of experience in the field, over which time they have learned many lessons that help ensure the success of subsequent projects. Johann van Biljon from Intaba Environmental Services says “we have worked with over 50 landowners undertaking river rehabilitation over the last 10 years. One landowner unfortunately planted Bottle Brush trees (Callistemon viminalis) after alien clearing had already taken place”. These trees are a listed invasive species, therefore it is utterly inappropriate as a restoration species (not to mention unlawful). “Another landowner planted hundreds of indigenous trees on second hand drippers from his vineyard and lost nearly all his trees due to irrigation failure in summer”.
Practical lessons learnt on riparian rehabilitation
Eradicate the invasive plants and remove threats to rehabilitation efforts. Learn about invasive alien plants (IAPs) (see resource links below) and ensure that you follow alien clearing methods that are recommended on the ‘Working for Water’ website. Specific herbicides and dosages are registered for different plant species and growth forms, stick to these specific chemicals and dosage rates. If you are not sure how to identify the plant species, use an app like iNaturalist, check out PlantZAfrica, consult your local Department of Agriculture representative or contact SANBI’s Directorate of Biological Invasions. Understanding the potential threats to your rehabilitation efforts is key: Are there livestock overgrazing the riparian zone? Are there too frequent fires? Is there an altered hydrology, due to over-abstraction? Find out the cause of the degradation, what is driving it and whether it may be mitigated.
Understanding riverbank dynamics, flooding and local systems is necessary, as there are different zones along a riverbank, secondary channels and various other hydrological and geomorphology aspects that need to be considered when rehabilitating riparian zones. Certain plants are suited to the wet bank zone and can be completely under water in flooding season, while others are better established in the dry bank zone that is flooded only rarely (e.g. during a 1:20 year flood event). Seek to understand the abiotic (climate, soil, etc.) and biotic factors (vegetation type, keystone species, etc.) in the system, as these all have an influence on how you undertake rehabilitation. The more you know about your natural environment the more you will be able to best navigate the task ahead.
Reshaping of modified or unnaturally shaped riverbanks (caused by erosion or the historical use of machinery) is sometimes necessary, but a challenge to correct. This ‘hard’ rehabilitation methodology may involve reshaping of banks using machinery, construction of gabion structures, weirs, and other structures. Just keep in mind that reshaping of riverbanks can only be done through authorisation from the Department of Environmental Affairs. This application can only be done through a registered environmental consultant and a freshwater specialist.
Planting methodology or ‘soft’ rehabilitation. Intaba has found that a combination of sowingof indigenous seeds and planting seedlings gives the best results. This also depends on your budget, site conditions and plant material available. If seeds are to be used, you need to understand sustainable harvesting methods, timing of seed maturation, seed treatment and germination methodologies in order to maximise successes. A permit from Cape Nature is needed to collect seed and plant material from natural areas. Plant selection and sourcing is further described below.
Timing of planting/sowing is also crucial. Planting and sowing are best done at the beginning of the rainy season, so that the plants have enough time to establish a good root structure to survive the dry season. However, if you have good irrigation and water supply, this can be manipulated. IAPs are very good at colonising disturbed ground, so it is best to plant and sow indigenous plants as soon as possible after IAPs have been removed in order to minimise the second wave of IAP infestation and/or secondary invaders from establishing.
Plant selection is a crucial aspect of riparian rehabilitation. You should only use local indigenous plants that occur naturally in the same river catchment, in the same riparian habitat and within the same specific soil type as on the rehabilitation site. This is necessary to preserve genetic integrity of plant species in the rehabilitation site and within the river itself. You don’t want to introduce a plant species that doesn’t naturally occur in that ecosystem, as these can potentially be invasive and out compete the local plants. A local freshwater ecologist/botanist or riparian rehabilitation specialist should be able to devise a suitable plant list for you. There are a few specialist rehabilitation nurseries and companies in the Western Cape, see list below.
Sourcing of plants. It is not easy to find locally-sourced plants on the market. Most plants that are produced in commercial nurseries are grown to look great, but may not be adapted to surviving in more harsh conditions. Many so-called “indigenous” species are hybrids of natural varieties that may, in fact, pollute the genetics of subsequent generations and even affect their wild relatives. It is best to ask a rehabilitation specialist where to source the right plants.
Irrigation is recommended for achieving higher success rates for active planting of plants on riverbanks. Preferably in-line drippers, as these are more reliable and don’t require much maintenance. Irrigation is needed in the first year to help the young plants survive during the dry months.
Soil additives will also help with the establishment of plants in eroded and degraded river systems to boost soil organic carbon. This is especially important if IAPs biomass was removed from the rehabilitation site (taking its stored carbon with it). You must use good quality organic compost, as pathogens and weeds that survive in second-rate compost can become an issue. Inoculated biochar is also another alternative that boosts soil health, but it is best to inoculate your biochar with local micro-organisms sourced from pristine habitats as close to the rehabilitation site as possible.
Fortunately, there is a global drive to restore degraded
ecosystems (the UN has just launched the Decade on Ecosystem Restoration 2021–2030),
with potential funding and support. There are some subsidised/semi-subsidised
programmes and organisations which are working on restoring rivers in South
Africa, namely Western Cape Department of Environmental Affairs and Development
Planning, Western Cape Department of Agriculture (LandCare), SANBI, FSC –
ReforestAction, GreenPOP, Wildlands, among others. Also there are global
organisations like the Society for Ecological Restoration (SER) that have
devised global standards for restoration and have resources to assist people
and organisations in devising restoration plans. The SER is developing an
African Chapter and this will hopefully support the UN Decade on Restoration.
In order to restore degraded ecosystems and rivers, you need to have a vision that it is never too late to make a change for the good. We are part of our environment and our future depends on it.
Society for Ecological Restoration (SER): https://www.ser.org/
Intaba Environmental Services: www.greenintaba.co.za
Invasive Alien Plants (IAPs): www.invasives.org.za
Indigenous plants: http://pza.sanbi.org/
Berg River Improvement Plan (WC DEA&DP): https://www.westerncape.gov.za/eadp/berg-river-improvement-plan-brip
Rehabilitation Nurseries/Contractors/Specialists in the Western Cape:
Prince Albert: Renu-Karoo Nursery (Sue Milton); Tulbagh: Intaba Environmental Services (Johann van Biljon); Stellenbosch: Envirowise (Lynda Muller); Worcester: Landcare Field Reserve & Nursery; Karroo Botanical Gardens; West Coast – Vula Environmental Services; Veld & Fynbos Nursery; Cape Peninsula – Cape Ecological Services (Patricia Holmes); Good Hope Gardens Nursery; Cape Flats Fynbos Nursery; Urban Landscape Solutions; Overberg: Green Futures Nursery.
Rebelo, A.J., Jarmain, C., Esler, K.J., Cowling, R.M., Le Maitre, D.C. 2020. Water-use characteristics of Palmiet (Prionium serratum), an endemic South African wetland plant. Water SA, 46(4):558–572.
Rebelo, A.J., Morris, C., Meire, P., Esler, K.J. 2019. Ecosystem services provided by South African palmiet wetlands: A case for investment in strategic water source areas. Ecological Indicators, 101:71–80.