How long do we think humans have been planting forests? A case study with Cedrus libani A. Rich

The cedar of Lebanon, Cedrus libani A. Rich, is distributed around the shores of the eastern Mediterranean in Turkey, Syria and Lebanon. The most anamolous aspect of its distribution is its presence in two patches in the Black Sea Region, approximately 500 km to the north of its main distribution in Turkey. Cuneiform tablets speak of an area which was turned into a land of cedar during the Hittite era, suggesting that the two patches might have been planted at that time. Genetic studies agree that these two patches originated at a later date than the cedars further south. Here, we make use of another means to test the hypothesis that the northernmost distribution of the cedar of Lebanon was due to reforestation during the mid-Holocene period. We determine distributional patterns for the species using a maximum-entropy algorithm and identify the most important environmental factors in shaping its distribution. We project the distribution of the species under the climatic conditions of the present, the mid-Holocene and the Last Glacial Maximum. We find the distribution range of the cedar of Lebanon to have shifted over time, encompassing western and southern Anatolia in the Last Glacial Maximum, then shrinking and retracting to the western Anatolia range in the mid-Holocene. The current range of the species was arrived at after the Holocene period. The projections support the possibility that the remnant forests in northern Turkey could have been created through reforestation, and that the Hittite myth may be substantiated.