Richard M. Bailey

Research pages

Complex environmental systems

In addition to work on Quaternary environments and ancient people, I have a strong interest in the more general properties of complex environmental systems, and particularly the nature of emergent properties  which lead to threshold-type behaviour. This interest has recently been focused on the modeling of semi-arid vegetation cover. The motivation for this is the central role played by vegetation in affecting the state of arid and semi-arid landscapes (past, present and future). Learning about past regime changes is an important component in our efforts to understand the more general workings of the Earth system. Understanding present day environmental systems and predicting transitions which may occur in the future (under increased climatic and human pressures, for example) is important in many contexts, and none more so than for the >1 billion people who depend on semi-arid vegetation for their livelihood.

 

Ongoing project: Cellular automata modeling of semi-arid vegetation

 

Many landscapes in semi-arid regions of the world are covered by vegetation which self-organizes in to a range of patterns. The patterns are most-likely due to the coupled effects of close-range facilitation and long-range competition for resources. Semi-arid vegetation is known to undergo rapid threshold-type collapse when under intense environmental stress and it is possible that changes in patterning may give leading indicators of immanent population collapse—this topic is the focus of much ongoing research in various institutions worldwide. Examples of vegetation patterns are shown below (all are screen captures from Google Earth, with a horizontal scale of ~500 m), from various locations within the African Sahel region (dark shades are the vegetation). I have used a newly-developed cellular automata model in which similar patterns occur naturally as a consequence of simulated changes in environmental stress. This model has been sued to explore the spatial and temporal evolution of patterning and plant density. Examples of model output are shown below.

 

Bailey, R.M. Spatial and temporal signatures of fragility and threshold proximity in semi-arid vegetation. (under review)