Remove bush and increase grazing capacity

Bush encroachment has affected large areas of savannah to such an extent that keeping livestock is no longer viable. Lindi van Rooyen looks at rehabilitation of grasslands.

Remove bush and increase grazing capacity
- Advertisement -

One of the greatest challenges facing livestock production, including game farming, in southern Africa, is bush encroachment. This is according to Arnaud le Roux, animal health and vegetation specialist with the Endangered Wildlife Trust. Bush encroachment occurs when woody plants, such as sickle bush and silver cluster leaf, take over, making it difficult for other plants to survive. Arnaud says that in a ‘structured’ (healthy) savannah, large trees can suppress the establishment of new seedlings, while maintaining the benefits of woody plants. These are soil enrichment and the provision of food for browsing herbivores. Bush encroachment upsets this balance.

Removing trees
Tree-on-tree competition must be kept in balance to curb or prevent encroachment. This is done by removing some trees, and all alien vegetation. Areas around the trees retained must be protected against encroachment. In this way, they can flourish and eventually create a stable structure in the environment.

Be careful which trees you remove, though, warns Arnaud. Certain trees must be retained to keep out exotic species. Clearing the area too ‘enthusiastically’, can be as bad as doing nothing at all, and will also result in an unstable environment that is detrimental to biodiversity.

- Advertisement -

Management plan
“It’s important to create a management plan to get rid of encroaching trees,” says Arnaud. First measure the area you’re ‘repairing’, then count all the trees. The number and species of trees you remove will depend on land usage. “Breeding camps require quality grass and specific trees at a certain density, depending on the number of animals. Selective mechanical and chemical control can be used to remedy encroachment in this case.” The people doing the bush clearing need to be shown exactly which trees to take out, once the plan has been put into place.

Chemical control methods
Frits van Oudtshoorn of Africa Land-use Training warns against the rapid establishment of tree seedlings after the removal of some of the mature woody plants. “In many cases, the resultant re-establishment of new woody seedlings may, over time, develop into worse encroachment than before. A follow-up is therefore needed,” he explains.

Take care when it comes to chemical control, as herbicides can contaminate the environment for many years. Herbicides can kill the wrong plants if not applied carefully, warns Frits. There are two main groups of herbicides: selective and non-selective. Those with one or more of these active ingredients are used in bush control: Picloram, Bromacil, Glyphosate, Tebuthiuron and Triclopyr.

Burning techniques
When it comes to removing trees and shrubs mechanically, large machinery such as a bulldozer is generally less selective, but faster than smaller machinery, such as brush-cutters, axes and chainsaws. Regular burning limits the growth of young woody trees and shrubs. Without it, encroaching species will take over. Fire, which often does not kill the plants, is used to ‘manipulate’ the bush canopy. It is done either to bring the canopy within reach of browsers or to facilitate the control of coppicing woody plants with chemicals.

In general, burning stimulates growth by removing litter and allowing more sunlight to reach plants, while increasing the soil temperature. A ‘hot’ fire on a hot, slightly windy day, will produce the best results. However, Arnaud warns that fire can also contribute to bush encroachment because heat causes the hard seeds of woody species to crack open, thus stimulating germination.

“To counteract this problem, browsers can be used before the fire as they will eat the seeds. “The management plan must continue after the fire and burning should only be used if perennial grasses are well-established,” he explains. Also, for safety sake, be sure that all burning takes place under expert supervision and complies with the relevant legislation.
Browsing animals, such as goats, eland, kudu, bushbuck and black rhino, as well as mixed feeders such as elephants, impala and nyala are effective in controlling woody vegetation naturally.

But Frits warns that goats are usually the only browsers that can be found in the required numbers and can be managed effectively to assist with bush encroachment. He adds that overgrazing, particularly the lack of veld rest, weakens grasses. This allows more bush saplings than usual to reach maturity and produce seed. “A healthy grass layer is vital for protecting the soil and suppressing seedlings,” he stresses.

Long-term commitment
Effective restoration of encroached areas is not a short-term project, but a long-term commitment. “Chopping down a few trees and using a bit of poison here and there won’t solve the problem. There’s no quick-fix – you need a management plan as well as a budget if you want to succeed,” says Arnaud. “But,” he adds, “the rewards pay off as the land becomes more productive and animals can flourish.”

This article is a short overview of measures to curb bush encroachment. For more information, contact Arnaud le Roux on 082 3256578 or Frits van Oudtshoorn on 078 228 0008.