Bush encroachment

At Malilangwe, certain animal species, like jackal, kori bustard, reedbuck, grass owl and secretary birds, depend on open grasslands for their survival. These grasslands, however, are threatened by encroachment of woody shrubs. On the reserve, woody plant cover in grasslands increased by 36% from 1963 to 1991. A combination of drought, heavy grazing by cattle and the exclusion of fire allowed woody shrubs to take over.

The increased level of carbon dioxide in the atmosphere since the 1960’s may have favoured the growth of woody plants relative to grasses, to the extent that certain species of shrubs now grow three times faster than they did in the past. This may be another reason why bush encroachment has been a problem in southern Africa for the past 60 years.

The reintroduction of fire at Malilangwe in 1994 has helped to control the establishment of new shrub seedlings, but fire has not been capable of killing already established plants. Although the above ground parts of shrubs are killed, they rapidly regrow by coppicing from their bases. For this reason, clearing by machine has become necessary in certain areas.