Thresholds Database > Grassland to woodland, Chobe National Park, Botswana

Background

Alternate Regimes

1. Grassland

2. Woodland

Mechanism

Switch from State 1 to 2: (e.g. early 1900's) Drought and rinderpest disease reduced herbivore numbers, enabling high grass growth. Hot fires and low elephant numbers allowed for the regeneration of trees.

Switch from State 2 to 1: (1960's) Woodland senesces through old age. Herbivores are maintained at high numbers, which does not allow for the regeneration of woody growth and the system starts returning to grassland.

Management Decisions in Each Regime

State 1: Artificial water points have been provided to mitigate the effects of drought and to help stabilise the system so that animal numbers do not get too high or too low. Animal populations are also spread more evenly over the landscape, reducing spatial heterogeneity. This, with the high numbers of herbivores maintained to promote conservation and tourism, the system is likely to stay in the grassland state (State 1).
Note: The transient phase (10-20 years?) during which there are high densities of both trees and elephants is the "state" of the system most desired by the resource users.