| Summary: | This research project studies the spatial and temporal relationships between climate and vegetation in the Tarhuna region of northwest Libya, in order to derive mathematical relationships describing vegetation dynamics over the study period 1981/1982-2005/2006. The study area straddles the Mediterranean and arid climate zones, and is prone to vegetation loss and land degradation due to drought and human activity. Rainfall has decreased over the period of study, leading to increased occurrence of drought and a greater risk of vegetation loss and land degradation. Rangeland and rain-fed agricultural land comprise 94% of the study area. Allowing for a two-month time lag, significant positive relationships between monthly climate and vegetation data (as measured by GIMMS NDVI archive) were found for both land cover types; the dominant control is the distribution and concentration of rainfall throughout the year. A positive relationship was found between annual rainfall and vegetation productivity. A water balance model, TVRWBM, was developed, and explained 70% of the variation of vegetation cover in the study area. By applying TVRWBM, three specific locations and time periods were identified where the model does not fit in particular years. Field investigations identified specific human activities as the cause for these anomalies. An attempt was made to use the model to predict future trends in land degradation using both statistical downscaling and GGM model predictions of future climate changes, but, although these methods can recreate temperature trend for the recorded period, they are not able to produce reliable estimates of rainfall. However, IPGG predictions suggest lower rainfall and higher temperatures for the study area in the future, so environmental pressures in the study area are likely to intensify.
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