Thresholds Database > Climate change with rooting depth, The Sahel, Africa

Certainty of shift: Proposed
Location: Africa, The Sahel
System Type: Social-Ecological
Regime Shift Category: 3a
Ecosystem Type
Spatial Scale
Type of Resource Use
Livestock Production
Number of Possible Regimes
Ecosystem Service
Time Scale of Change
Resource Users
Reversibility of Shift


An extended period of drought has persisted in the Sahel since the 1960's.

Alternate Regimes

1. Self-sustaining wet climate equilibrium with deep-rooted perennial grasses

2. Self-sustaining dry climate equilibrium with shallow rooted grasses

Fast or Dependent Variable(s)
Slow or Independent Variable(s)
Rooting depth
Disturbance or Threshold Trigger(s)
Variable climate, grazing pressure
External / Internal Trigger


The combination of natural climate variability and the change in land cover have combined to result in dryer climatic conditions in the Sahel. Vegetation type, rooting depth and climate are linked in the model, such that moist growing seasons are associated with abundant root biomass. Less root biomass has less above ground growth and a smaller leaf area. Less water is therefore transpired to the atmosphere, providing less atmospheric moisture to the biosphere, resulting in the system remaining in a dryer state.

Management Decisions in Each Regime

Jacqui Meyers


CSIRO Sustainable Ecosystems,
PO Box 284,
Canberra ACT 2601

descriptive, Ecosystem Management, Physical/Climate, deforestation


Wang, G. L., and E. A. B. Eltahir. 2000. Role of Vegetation Dynamics in Enhancing the Low-Frequency Variability of the Sahel Rainfall. Water Resources Research 36, no. 4: 1013-21.

Higgins, P. A. T., M. D. Mastrandrea, and S. H. Schneider. 2002. Dynamics of Climate and Ecosystem Coupling: Abrupt Changes and Multiple Equilibria. Philosophical Transactions of the Royal Society of London Series B-Biological Sciences 357: 647-55. (D)