Bush encroachment & Erosion control – Read more here

Humans cause huge disturbance to the natural bush by cultivating fields, building roads, dams and carrying out farming practices. These activities can alter the bush to such an extent that is becomes us-useable to the indgenous species. Over-grazing by cattle leads to the natural plant cover being damaged and the soil exposed. Incorrect burning practices and drought can also contribute to soil exposure. Weathering processes then lead to leaching and nutrient run-off making the soil useless and un-productive. Other natural areas effected by human interference become vulnerable to bush encroachment where the natural balance between grass and woody components is altered. Causes of bush encroachment include over-grazing, drought, misuse of burning, an absence of browsers or incorrect positioning of waterholes. Severely eroded and degraded areas may take years to recover naturally, if they recover at all.

Project aims:

Rehabilitation of previously over grazed and damaged/encroached areas to achieve well structured, diverse, healthy and productive vegetation.

What’s being done?                                                                                                                                                                                                                                                                                 

  • Bush encroachment – Bush encroached areas on Pidwa are identified and can then be managed in a number of ways. Most commonly, encroaching species are removed by mechanical means. These species can also be targeted with biological control (using a natural pest or browser pressure), fire control or as a last resort using chemicals.
  • Erosion – Eroded sites are identified and targeted for rehabilitation. Firstly, the exposed and leached soil is picked either using hand picks or machinery. Where possible the gradient of any slopes is reduced to minimise surface run-off. Next the soil must be covered with plant matter; removed bush encroached species are often perfect for this and usually carry spines and thorns enhancing their effect. This plant cover performs many functions starting with a physical barrier to any animals moving across the soil while it’s trying to recover. It also prevents evaporative loss, slows surface run off and protects against splash erosion. Even when dead, the plant cover contributes to the soil improving its structure, water holding ability and nutrient content. Eroded areas can be seeded artificially but this is not essential; grass seeds will naturally be blown to the area. The planting of small trees can also assist rehabilitation as the roots will begin to bind the soil and cycle nutrients.


 The role of volunteers:

  • Bush encroachment control – Areas for control are identified and volunteers assist with removal of encroaching species. Pangas and bow saws are used and the branches are then transported to where needed. Where possible an erosion site is rehabilitated in conjunction with bush encroachment control taking place so the branches can be used as plant cover on the eroded area.
  • Erosion rehabilitation – Volunteers prepare the eroded soil by picking and reducing the gradient of any sloping ground. Branches of encroaching species are then packed on top of the soil in a very particular way to maximise protection. Where needed, extra seed is spread and sapling trees sometimes planted.
  • Monitoring – Once an eroded area has been rehabilitated it cannot just be left. Continual monitoring must take place to check that the process has worked and any areas where it hasn’t must be re-done. Any sapling trees planted will need watering until such a time that they are able to establish their own roots.


© Askari Wilderness Conservation Programme

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