Palynological evidence for vegetational history in semi-arid areas of the western Mediterranean (Almeria, Spain)

Three sedimentary sequences from the southeastern littoral of the Iberian Peninsula have been palynologically studied. The results obtained show that during the Holocene no significant forest cover existed in the studied area, so that the different phases identified mainly show an alternation of shrub formations and steppe communities probably determined by limitations that are fundamentally bioclimatic. Highest values of arboreal pollen at the bottom of the San Rafael sequence would correspond to an older period, when the area appears to be dominated by shrub communities with a high proportion of wild olive, whereas at the beginnings of the Holocene it is dominated by steppe formations. Between 7000 and 4500 yr BP the Holocene optimum is recorded, with a significant degree of vegetational cover. This period ends abruptly with a radical transformation of the landscape that reflects the establishment of the steppe conditions that persist today, which lead to the marginalization of the maquis and the impact of intense erosion processes on a gradually deforested countryside.