We would like to inform guest’s as well as nationals on the growing issue regarding the encroachment bush issue currently burdening Namibia’s landscape. This topic is not taken lightly by most or actually all landowners of Namibia. Discussed here is the species known in Latin as Acacia mellifera, English: Blackthorn, Oshiwambo: Omunkono, Otjiherero: Omusaona, Khoekhoegowab: !noes and in Afrikaans as Swarthaak. Bush encroachment is the invasion and/or thickening of aggressive undesired woody species resulting in an imbalance of the grass to bush ratio, a decrease in biodiversity, a decrease in carrying capacity and concomitant economic losses. Namibia is the aridest country south of the Sahara, with scarce and unpredictable rainfall, and perennial rivers only on its borders. Over 80% of Namibia’s land area relies solely on groundwater for any economic productivity. Extensive bush encroachment, together with the effects of climate change, is putting further pressure on water resources. The Namibian agricultural sector has the potential to increase economic production provided that extensive thinning of encroacher bush is implemented – in order to restore the former carrying capacity and restore the natural recharge potential of groundwater. However, the potential benefits of bush thinning extend into other economic sectors as well.
“Near the village of Gawukeni, in the Eastern Cape Province, South Africa. Shrubs and low trees have invaded the abandoned fields in the centre of the image resulting in extensive ‘bush encroachment’ which is widespread in the region. The original photo was taken by D.M. Commins in 1958 and the repeat photograph by PCU PhD candidate James Puttick 53 years later in 2011.” (by University of Cape Town)
Bush encroachment is severely hampering the red meat industry of Namibia and it is also negatively affecting biodiversity and the recharging tempos of certain aquifers. More than 40 million hectares of Namibian rangelands and Savannah has been degraded by encroacher bush. There is a considerable market demand for biomass in the world and the use of waste wood or unwanted woody biomass has become a sought-after commodity, mainly because of its low to a positive impact on the environment when used as a heat source. Read this article giving a deep insight into Farmers struggling to manage this ever-growing problem.
BOTANIC DESCRIPTION: Acacia mellifera is a low, branched tree with a more or less spherical crown. Black bark on stem becomes ash-grey to light brown on the branches, bearing small, short, sharply hooked spines in pairs. It has a shallow but extensive root system radiating from the crown, allowing the plant to exploit soil moisture and nutrients from a large volume of soil. The roots rarely penetrate more than 1 m. Apparently, this bush has somehow made it to Namibia, hence it isn’t an indigenous Plant within the southern parts of Africa (debated along Botanist’s hence their Latin classification of “Acacia” ?). It nevertheless is creating a massive problem within the southern Africa Fauna & Flora. Creating huge problems for the Agricultural and Wildlife field.
Acacia mellifera is a commonly occurring shrub on rangelands throughout the savannah in western, eastern and southern Africa. The terrain preference is rocky hillsides with rainfall along seasonal watercourses, mixed with other trees. If left unattended, especially if grazing is heavy and no fires check its spread, it may form dense, impenetrable thickets, 2-3 m high and sometimes hundreds of metres across, slowly taking over good grazing land. This species is extremely drought-tolerant.
The removal of encroaching bush from the Namibian rangelands would not only be regarded as an attempt to restore the savannah and its biodiversity, it would also be advantages to the subsurface water resources of affected areas. It is therefore important that methods to economically harvest biomass from encroaching bush is currently being addressed by the Namibian Ministry of Agriculture. Due to the certain years of drought throughout Namibia, the Swarthaak bush is now growing fiercely and this further overcrowds the lands and leaves no space for the natural grass to grow. Farmers and Landowners then learned that they have to come up with a brilliant solution to this problem and save their cattle from dying and at the same time de-bush their land. Bush encroachment hinders productivity on some of the commercial farms sampled, reduces underground water, and has negative effects on the Namibian economy. Results shown on Government surveys carried out with selected targeted farms demonstrate that farmers are using a range of methods to combat bush encroachment, each with limited results: Methods include 1. Burning, 2. Removal via Machinery, or via 3. Pesticides / Chemical applications (least favoured hence it filters down to the groundwater reserves).
It is generally accepted that the decline in the carrying capacity of our rangelands could be as much as 100% or more (a decrease from 10 ha per LSU too, for example, 20 to 35 ha per LSU). It is generally studied and so with accepted that on a day with good rainfall the Blackthorn or Swarthaak takes up at least 70% of the available rainwater. Therefore, at a conservative production loss of only 3 kg carcass weight per hectare and at 2002 prices (2018 prices currently not available). Namibia is suffering a loss in income of more than N$700 million per annum (LSU = Life Stock Unit). Bush encroachment should, therefore, be regarded as a societal problem to be addressed with strong support at a national level (the calculations estimate is predicated on a triple increase on the mentioned amount for the year 2018). Water shortage is always giving a constant problem and worries for the Namibian Farming community. Unfortunately, the issue of water shortage is becoming a massive global issue, for this Blog Post we are going to focus on the mentioned issue at hand. Read this informative Newspaper article for a deeper insight regarding this urgent matter!
The overwhelming factor determining the spatial distribution and productivity of forest savannas and grassland is soil moisture balance. This balance and, therefore, the soil water content have largely been disturbed by invader bush, resulting in very little efficiency in respect of water use on natural rangelands. Research findings in African savannas showed that rangelands in poor condition, i.e. bush-encroached, need three to four times more water to produce the same amount of grass compared with veld that is in an optimum state.
This problem is further accentuated given the erratic climatic features of Namibia, where – • low average rainfall • high evapotranspiration • large fluctuations in rainfall between and within years, and • low rainfall predictability have a drastic impact on the stability of people’s livelihoods.
Please do not confuse the Camelthorn Tree (Acacia erioloba) with the Swarthaak (Acacia Mellifera) these are two very different botanical species. The Camelthorn Tree of Namibia is much beloved and gives the impression to seem harmless, offering a delicious meal for hungry desert-dwelling wildlife. But don’t underestimate these beautiful trees, they are indeed very clever. On the moment when wildlife animals start snacking on the Acacia leaves, this beautiful tree goes into self-defence mode by secreting a sharp garlic-like odour as a defence mechanism which in turn repels animals. The Camelthorn tree is extremely slow growing due to the harsh Namibian environment. It deserves the utmost respect and should not be seen as an encroaching botanical species like the Swarthaak. The Acacia Erioloba carries the same pre-name “Acacia” but is not an invasive species!!
+ People making a change:
In many ways, we therefore kindly ask the International society to have a look at the below-linked undertaking and offer their support as far as possible. These individuals are trying a serious attempt to create a change and all help is much appreciated…
Some interesting Namibian Newspaper articles and .pdf’s regarding Bush encroachment:
Namibian Company link selling Encroachment Bush by-products or services:
Although there are a couple more companies out there trying to help with the bush encroachment problem, the impact on the issue still remains far too small to make a true difference.
Image rights for explanatory Graphics / Posters (middle): DAS Namibia