Mediterranean landscape 6,000 years ago

Collins, Davis, and Kaplan map differences in Mediterranean and southern European vegetation beween 6,000 years ago and the present. The goal: to determine just how different the Mediterranean landscape was 6,000 years ago, before the rise of Western civilization. The findings: it was different, but less than is commonly believed.

Aim: To contribute to the intense debate surrounding the relative influence of climate and humans on Mediterranean-region land cover over the past 6,000 years, we assess the Holocene biogeography and vegetation history of southern Europe by means of an extensive pollen record dataset.

Location: The Mediterranean biogeographical zone and neighbouring parts of Iberia, the Alps, and Anatolia, between 30° N, 48° N, 10° W and 45° E.

Methods: We compiled a southern European pollen record dataset using available pollen databases (121 sites) and other sources (76 sites), with improved spatial coverage and dating control compared with earlier studies. We used only those sites that had pollen data for both 0 ka and 6 ka. We reconstructed mid-Holocene and present-day biomes, arboreal pollen percentages, and distribution and relative abundance of 11 key woody taxa, with anomaly maps.

Results: Northern temperate forest biomes extended further south at the mid-Holocene than at present, but not as far as earlier studies suggested. Sclerophyllous vegetation occurred along the Mediterranean coast throughout the region at 6 ka. Arboreal pollen percentages were up to 50% higher than at present. At 6 ka, Olea, Fagus and Juniperus had smaller distributions and/or abundances; Abies, Cedrus and both deciduous and evergreen Quercus had larger distributions and/or abundances; Phillyrea, Pistacia and Cistus showed minimal difference; and Pinus showed a cosmopolitan distribution with variable abundance.

Main conclusions: Temporal difference analysis is more meaningful when only sites containing samples for all time slices are analysed. During the mid-Holocene, southern Europe was more heavily forested with temperate vegetation than it is at present, but drought-tolerant xeric vegetation was still widespread along the southern margins of the region. Although human land use may have caused land degradation between the mid-Holocene and the present, the mere presence of xeric vegetation in the Mediterranean region does not require human impact. This challenges the commonly held belief that modern Mediterranean vegetation represents a “degraded” state.

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