This study reconstructs and interprets the changing range of Atlas cedar in northern Morocco over the last 9,000 years. A synthesis of fossil pollen records indicated that Atlas cedars occupied a wider range at lower elevations during the mid-Holocene than today. The mid-Holocene geographical expansion reflected low winter temperatures and higher water availability over the whole range of the Rif Mountains relative to modern conditions. A trend of increasing aridity observed after 6,000 years BP progressively reduced the range of Atlas cedar and prompted its migration toward elevations above 1,400 masl. To assess the impact of climate change on cedar populations over the last decades, we performed a transient model simulation for the period between 1960 and 2010. Our simulation showed that the range of Atlas cedar decreased by about 75% over the last 50 years and that the eastern populations of the range in the Rif Mountains were even more threatened by the overall lack of water availability than the western ones. Today, Atlas cedar populations in the Rif Mountains are persisting in restricted and isolated areas (Jbel Kelti, Talassemtane, Jbel Tiziren, Oursane, Tidighine) that we consider to be modern microrefugia. Conservation of these isolated populations is essential for the future survival of the species, preserving polymorphisms and the potential for population recovery under different climatic conditions.

The present study aims to review palaeoecological evidence for environmental changes induced by human activities over the last few millennia in the montane landscapes of Morocco. The study is based on well-dated pollen and geochemical records from the Rif and the Middle Atlas mountains, to show spatial and temporal variation in the onset and intensity of exploitation of forest, soil and mineral resources. Before ca. 2000 BP, anthropogenic impact was minimal. At about that time, abrupt changes of the arboreal pollen proportions, with a decline in all tree taxa, indicate a reduction of the forest cover interpreted as being anthropogenic. In the Rif Mountains, increased influx of carbonates (Ca) in the sedimentary records indicates enhanced soil erosion coincident with the reduction in tree cover. In the Middle Atlas, reduced forest cover is linked to geochemical evidence for mining and metallurgy of lead (Pb), copper (Cu) and zinc (Zn). These industrial activities correspond to the expansion of the Roman Empire into Morocco at around AD 40 and show a decline when the Romans were displaced by the Vandals about five centuries later

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