If gum trees are water guzzling, biodiversity-killing alien plants, why are there still thousands standing across the Garden Route? South investigates the misconceptions about and benefits of Eucalyptus trees, as well as the reasoning behind recent legislative changes that no longer require their outright eradication, but still speaks for responsible management by landowners.
WORDS Francini van Staden PHOTOGRAPHS Desmond Scholtz
It holds true that as an alien tree species, Eucalyptus has the potential to compete with indigenous plants. At least
85 different gum species have been introduced in South Africa since the 1800s for commercial forestry and horticultural purposes. There is no longer Eucalyptus afforestation in the Garden Route but the use of these trees as fire belts – harnessing eucalypts’ allelopathic ability to reduce the fuel load at ground level surrounding pine plantations – resulted in thousands of wild trees, and many geometric belts of eucalypts throughout the region. The most prominent species in the Southern Cape remains E. grandus or Flooded Gum, E. diversicolor or Karri Gum and E. globulus or Blue Gum.
“People commonly think other plants cannot grow underneath Eucalyptus trees because they consume all available water, depriving surrounding vegetation of water,” says Professor Josua Louw, director of the Nelson Mandela Metropolitan University (NMMU)’s School of Natural Resource Management. The bare patches often seen below eucalypts arenot the results of water guzzling, but rather eucalypts’ allelopathic ability. “Eucalypts release allelochemicals that prevent or slow down the growth of other plants underneath its mature canopies. They are a particularly serious threat in riparian zones where there are high levels of water availability, but they equally occur in drier zones where they consume less water. Their water consumption rates are furthermore influenced by weather, species, competition and age.”
Scheduling for tolerating and eradicating
Although an introduced alien tree species, not all eucalypts are considered invasive. “In the Garden Route National Park, SANParks consider the Red River Gum (E. camaldulensis) and the Karri Gum as invasive species because of rate of spread,” says SANParks vegetation ecologist Tineke Kraaij. Ecologists are most concerned about those species that invade environments, threatening natural resources such as water, biodiversity, agricultural and soil potential. “Gums, being large trees, consume more water than indigenous fynbos vegetation. Rehabilitation of areas that were planted with gums also proves to be very challenging due to the gums’ ability to coppice vigorously and their allelopathic effects inhibiting natural recovery of the indigenous vegetation.”
The full extent of impacts are not yet fully understood, especially since alien species can have positive economic impacts, as guided by the Alien and Invasive Species Regulations released in October 2014, under the auspices of the National Environmental Management: Biodiversity Act (2004).
This new categorisation lists various Eucalyptus species as Category 2 and 3 species, meaning they can be tolerated under certain circumstances. “These changes in legislative scheduling of eucalypts were made because of its commercial forestry status. Its economic value is further validated, including its functions as windbreaks and a source of nectar for bees. Their carbon sequestration potential could also feature more prominently in the future,” says Josua. There are, however, circumstances where Eucalyptus are categorised as Category 1b – the ‘must-eradicate’ category. Riparian and conservation worthy zones are such priority circumstances, where it is critical to remove and avoid any regeneration to stop unwanted spreading. “The Flooded Gum in particular spreads fast in catchment areas,” says Josua. It also creates a potential erosion problem. “Unlike indigenous riparian vegetation, Eucalyptus cannot bend over; the trees become entirely uprooted during floods, causing severe erosion and river flow disruptions.”
Apart from this amended legislation, the Conservation of Agricultural Resources Act (1983) and the National Water Act (1994) also obligate landowners, whether state or private, to take responsibility. But controlling invasive alien species is a mammoth task. “It is therefore necessary to prioritise the aggressive invaders and habitat types that are most susceptible to the impacts of invasive species,” says Tineke.
Assistance for landowners
The Southern Cape Landowners Initiative (SCLI), an invasive alien clearing focus group, aims to assist landowners with this responsibility. “Our key focus is the Garden Route’s riparian and biodiversity zones, where we aim to lessen the negative ecological impacts of invasive alien species,” says SCLI chairman Cobus Meiring. “We assist landowners where they need information or input for clearing and managing alien species. Although we can assist in referring contractors, landowners remain responsible for the cost of alien clearing, which varies between R4000 and R10 000 per hectare.”
From timber waste to eco-desk
With legislative focus on invasive and alien plant clearing, several alien tree-clearing programmes were initiated over the past decades. This gave rise to value-added industries, such as the Farleigh Eco-Furniture project outside Knysna, which started in 2011. “We harvest Eucalyptus timber that would otherwise have gone to waste for the purpose of manufacturing school desks. The project clears about 500 wild and mature eucalypts per month, from which a hundred school desks are made daily,” says Farleigh mill manager Herman Jungbauer-Rudman. Although aesthetically pleasing, processing Eucalyptus hardwood timber can be problematic. “End splitting, brittle heart, gum canals, cell collapse and dimensional stability are some of its timber challenges, but is still favoured for its high surface wearing quality together with pleasing textures of interlocking grain and curly grain,” explains Richard Müller, wood technology programme coordinator of the NMMU School of Natural Resource Management.
The Farleigh Eco-Furniture project uses timber from historic fire belts surrounding pine plantations throughout the Garden Route. “The plantation fire belts alone will offer another eight years’ worth of timber and there is more available – we haven’t even started considering Eucalyptus that private landowners would want removed,” says Herman. Farleigh Eco-Furniture is an industry pioneer, and following from its success are four more eco-furniture factories starting up throughout the country.
Eucalyptus is a species of potential value, but also of potential harm. Where mature individual trees contribute positively to the landscape or environment, consideration should be given to responsible management rather than removal. Taking a precautionary approach will allow people to tap into the trees’ benefits while still contributing to curbing their negative ecological impacts. The industry and scientists agree: the solution is realising that both economic value and ecological integrity should be played out for sustainable management.
To fell or not to fell?
In the following environments, Eucalyptus trees do not need to be felled:
in arid Karoo environments where they offer benefits such as shade and bee foraging resources;
in cultivated landscapes and outside a 50m radius from indigenous vegetation;
within 50m of existing farmsteads;
in urban environments with a tree trunk diameter of more than 400mm measured at a height of 1000mm;
All commercial forestry plantations are exempted from felling; and
Old or large trees may be protected under the South African Heritage Resources Act (Act 25 of 1999); property owners will need to apply for a permit authorising the removal of such an individual tree.
Where Eucalyptus trees must be felled:
All riparian zones, national parks, conservation areas, or ecosystems categorised as conservation worthy ecosystems in terms of biodiversity management plans.
Professor Josua Louw
NMMU School of Natural Resource Management
044 801 5019