Database
 

Thresholds Database > Climate change with deforestation, West Africa

Certainty of shift: Proposed
Location: West Africa (southern coast), Nigeria, Ghana, Ivory Coast
System Type: Social-Ecological
Regime Shift Category: 3a
Ecosystem Type
Forest/Woodland
Spatial Scale
Sub-continental/Sub-regional
Type of Resource Use
Forestry
Number of Possible Regimes
2
Ecosystem Service
Food and fibre (agriculture, forestry), fuel (wood)
Time Scale of Change
Years
Resource Users
 
Reversibility of Shift
Irreversible

Background

This study illustrates that relatively small areas of land cover can determine the equilibrium state of the atmosphere-biosphere system of an entire region. Increases in population have resulted in land clearing for agriculture and timber harvesting for domestic and commercial use. In the early 1900's, rainforest covered about 500,000km2. by the end of the 20th century, less than 10% of the primary rainforest remained.

Alternate Regimes

1. Monsoons

2. Reduced rainfall


Fast or Dependent Variable(s)
Rainfall
Slow or Independent Variable(s)
Net surface radiation, entropy flux
Disturbance or Threshold Trigger(s)
Logging
External / Internal Trigger
External

Mechanism

Deforestation along the southern coast of West Africa may result in a reduction in regional rainfall and a possible collapse of monsoon circulation. Deforestation reduces the net surface radiation and entropy flux, resulting in a decrease of boundary layer entropy and rainfall over the coastal land, limiting the northward extension of the Intertropical Convergence Zone.

Management Decisions in Each Regime



Contact
Jacqui Meyers

Email
jacqui.meyers@csiro.au

CSIRO Sustainable Ecosystems,
PO Box 284,
Canberra ACT 2601

Keywords
descriptive, conceptual model, Ecosystem Management, Physical/Climate, deforestation

References

Zheng, X. Y., and E. A. B. Eltahir. 1997. The Response to Deforestation and Desertification in a Model of West African Monsoons. Geophysical Research Letters 24, no. 2: 155-58. (M)

Zheng, X. Y., and E. A. B. Eltahir. 1998. The Role of Vegetation in the Dynamics of West African Monsoons. Journal of Climate 11, no. 8: 2078-96. (M)

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)