A farmer's experience with bush encroachment

Farmer David Addenbrooke has worked in the Zimbabwean beef industry for around four decades. Here, he relates his experience with bush encroachment and offers farmers some advice on battling this scourge.

- David Addenbrooke

When it comes to bush encroachment, I prefer the term 'woody plant proliferation', as this is a process of changing vegetation and changing habitat over which every farmer has very little control.

The causes of woody plant proliferation shift constantly, depending on many factors. Zimbabwe offers a unique example of these changing circumstances. In the pie charts accompanying this article, I have taken the unscientific liberty of interpreting what I consider to be the principal driving forces behind woody plant proliferation in Zimbabwe.

Of course, as I have only been around since 1956 and only actively observant since 1978, the period from 1900 to 1980 has a few holes in it.

THE INFLUENCE OF FIRE/SOIL TEMPERATURES ON GERMINATION OF WOODY PLANT SPECIES

The wattle tree (Acacia mearnsii) originated in Australia. At maturity, around seven years old, the bark can be stripped off and taken to an extraction factory to recover the tannins. Trees are then skilfully cut to fall in longitudinal lines across the land/block.

The largest logs are taken to fire boilers at the extraction factory, for example, or to make furniture, while the remaining brush and logs are left to dry in preparation for burning within the block. Once the summer rains are acknowledged as 'under way,' these lands are set alight. To ensure that there is satisfactory and evenly dispersed heat, the fire is set as a 'ring' around the entire land.

Within a period of 10 to 20 days, the land changes from a black and burnt landscape to a carpet of green wattle saplings.

Research shows that while not all