Evaluating the Impact of Drought Using Remote Sensing in a Mediterranean,Semi-arid Region

This paper analyses monthly differences in drought impact on vegetation activity in a semi-arid region in the north-east of the Iberian Peninsula between 1987 and 2000. The study determines spatial differences in the effects of drought on the natural vegetation and agricultural crops by means of the joint use of vegetation indexes derived from AVHRR images, a drought index (standardized precipitation index), and Geographic Information Systems. The results show that the effect of drought on vegetation varies noticeably between areas, a pattern that is determined mainly by the location of land-cover types. The influence also varies each month and, in general, is higher during the spring and summer. Aridity and vegetation characteristics similarly account, in part, for spatial differences in the impact of drought on vegetation. In general, the most arid areas, where vegetation cover and activity are low, are those in which the interannual variability of vegetation activity is more determined by the drought occurrence. In assessing drought impact, this analysis takes into account the effects of drought on the vegetation and also considers spatial and seasonal differences. The results should be useful for the management of natural vegetation and crops and for the development of better drought mitigation strategies.