Conservation and sustainable bush-thinning
Okonjima Nature Reserve aims for a healthy, balanced ecosystem of bushveld and grass, as excessive bush thinning is not as good as one may think.
STAFF REPORTER
WINDHOEK
The Okonjima Nature Reserve in Otjozondjupa Region has been practising bush thinning for conservation and tourism and has perfected its process for maximum results and minimum environmental impact.
Based on the reserve is the Africat Foundation, which also conducts ecological research focusing on rare and endangered species.
“I have learnt the hard way at times; it is very sad to see the effects of the incorrect ways of doing bush thinning,” says Wayne Hanssen, the co-owner of Okonjima and AfriCat founder.
Hanssen says that as a tourism and conservation operation, there have been many benefits to perfecting their process.
“If you have a game farm, the biggest conservation benefit of bush thinning is that you do not need to keep as much game on your farm. If you have not thinned, you need so many more of each species, and this leads to overgrazing. You need about 10 hectares per animal, any more than that and the game will destroy your grasses in the years of drought. So bush thinning allows you to have much fewer animals on your farm and have a quality game drive.”
Combining strategies for diversified ecosystems
At AfriCat a combination of methods is used for maximum results. “I have seen that there is not one method that works alone. It is a combination of methods and adaptations,” says Hanssen.
“If you live in an area with upwards of 400 mm of [annual] rainfall, then a completely open grassy plain is a floodplain. A naturally occurring flood plain has a different composition of soil due to the regular flooding; tree roots battle to penetrate this soil and only certain grasses would be found in these areas. In our area, we live with bushveld, and you want some bushveld on your game farm because it has value to your wildlife.”
According to him, having a combination of bush and grass is of vital importance.
“There is a benefit to having some bushveld, and not only grass plains. Ecosystems flourish in a mixed-use space. Bushveld becomes shelter for animals in the cold, and we have found that animals survive on bush until the rains come and the grasses grow. In times of drought, even some of our pure grazers switched to browsing.”
With this understanding of the value of a diversified ecosystem, Hanssen recommends the method they have used at Okonjima Nature Reserve, being a combination of using a tyre dozer and roller.
“With bush rolling you selectively drive over the bush, roll it flat and then leave it right there. When you roll flat, you protect the soil and give the grass opportunity to germinate where no animals can get to it. It also prevents soil erosion by providing shade for the soil, and guides rainwater into the ground. Shade, water and protection.”
The science behind Wayne’s method
Hanssen, an avid researcher, explains the added benefits of his methods to the ecosystem.
“Acacia mellifera (Blackthorn or Swarthaak) and Dichrostachys cinerea (Sicklebush) are the two biggest problem species with bush encroachment, but I was amazed to learn that the acacia tree is actually a legume, and so it has the ability to take nitrogen out of the air and through bacteria in the soil, can put nitrogen back into the soil.”
He says when an acacia is flattened, you will find a burst of regrowth in the vegetation around the rolled bush, as the roots release nitrogen into the soil, and you will have a burst of growth in grass species around the area that you have rolled. Nitrogen, phosphorus and potassium are the three most important nutrients for plants. This combined with the protective nature of leaving the rolled bush in the veld, provides a sanctuary for diverse grass regrowth.
“For any farm you want about 80 to 100 Acacia mellifera per hectare. So, depending on the thickness of your bush, you want to leave all the trees but take out about 60% of your mellifera species. Mellifera has a shallow root system with a high extraction of water out of the soil, but don’t take everything out, because you will destroy the soil.”
Hanssen is also vehemently against using poisons, because of their long-term negative effects. He explains that even up to ten years later, poison can make its way into the underground root system of your trees and they can die. This can happen when using poison on one part of your farm that gets carried with rainwater into places not intended.
“The rains take the poisons into the root systems of your big camelthorns and they die off years later. Their root system is so widely spread. It was devastating for us to lose these trees, so I am dead against herbicide for bush thinning.”
WINDHOEK
The Okonjima Nature Reserve in Otjozondjupa Region has been practising bush thinning for conservation and tourism and has perfected its process for maximum results and minimum environmental impact.
Based on the reserve is the Africat Foundation, which also conducts ecological research focusing on rare and endangered species.
“I have learnt the hard way at times; it is very sad to see the effects of the incorrect ways of doing bush thinning,” says Wayne Hanssen, the co-owner of Okonjima and AfriCat founder.
Hanssen says that as a tourism and conservation operation, there have been many benefits to perfecting their process.
“If you have a game farm, the biggest conservation benefit of bush thinning is that you do not need to keep as much game on your farm. If you have not thinned, you need so many more of each species, and this leads to overgrazing. You need about 10 hectares per animal, any more than that and the game will destroy your grasses in the years of drought. So bush thinning allows you to have much fewer animals on your farm and have a quality game drive.”
Combining strategies for diversified ecosystems
At AfriCat a combination of methods is used for maximum results. “I have seen that there is not one method that works alone. It is a combination of methods and adaptations,” says Hanssen.
“If you live in an area with upwards of 400 mm of [annual] rainfall, then a completely open grassy plain is a floodplain. A naturally occurring flood plain has a different composition of soil due to the regular flooding; tree roots battle to penetrate this soil and only certain grasses would be found in these areas. In our area, we live with bushveld, and you want some bushveld on your game farm because it has value to your wildlife.”
According to him, having a combination of bush and grass is of vital importance.
“There is a benefit to having some bushveld, and not only grass plains. Ecosystems flourish in a mixed-use space. Bushveld becomes shelter for animals in the cold, and we have found that animals survive on bush until the rains come and the grasses grow. In times of drought, even some of our pure grazers switched to browsing.”
With this understanding of the value of a diversified ecosystem, Hanssen recommends the method they have used at Okonjima Nature Reserve, being a combination of using a tyre dozer and roller.
“With bush rolling you selectively drive over the bush, roll it flat and then leave it right there. When you roll flat, you protect the soil and give the grass opportunity to germinate where no animals can get to it. It also prevents soil erosion by providing shade for the soil, and guides rainwater into the ground. Shade, water and protection.”
The science behind Wayne’s method
Hanssen, an avid researcher, explains the added benefits of his methods to the ecosystem.
“Acacia mellifera (Blackthorn or Swarthaak) and Dichrostachys cinerea (Sicklebush) are the two biggest problem species with bush encroachment, but I was amazed to learn that the acacia tree is actually a legume, and so it has the ability to take nitrogen out of the air and through bacteria in the soil, can put nitrogen back into the soil.”
He says when an acacia is flattened, you will find a burst of regrowth in the vegetation around the rolled bush, as the roots release nitrogen into the soil, and you will have a burst of growth in grass species around the area that you have rolled. Nitrogen, phosphorus and potassium are the three most important nutrients for plants. This combined with the protective nature of leaving the rolled bush in the veld, provides a sanctuary for diverse grass regrowth.
“For any farm you want about 80 to 100 Acacia mellifera per hectare. So, depending on the thickness of your bush, you want to leave all the trees but take out about 60% of your mellifera species. Mellifera has a shallow root system with a high extraction of water out of the soil, but don’t take everything out, because you will destroy the soil.”
Hanssen is also vehemently against using poisons, because of their long-term negative effects. He explains that even up to ten years later, poison can make its way into the underground root system of your trees and they can die. This can happen when using poison on one part of your farm that gets carried with rainwater into places not intended.
“The rains take the poisons into the root systems of your big camelthorns and they die off years later. Their root system is so widely spread. It was devastating for us to lose these trees, so I am dead against herbicide for bush thinning.”
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