Fragility of Western Mediterranean landscapes during Holocene Rapid Climate Changes

In this paper we explore the evidence for Holocene Rapid Climate Changes (RCCs) in Western Mediterranean records, examining similarities and differences in the timing and nature of impacts on different components of the natural environment (vegetation, fluvial and coastal sedimentation, fire activity, soil formation). Marine, lacustrine, and fluvial archives of the Western Mediterranean (Iberian Peninsula and Northwest Africa) provide evidence for both pervasive millennial-scale climatic variability and abrupt (decadal- to centennial-scale) transitions. We focus in particular on three RCCs characterised by high-latitude cooling, glacier advances and North-Atlantic ice-rafting events: the mid-Holocene RCC interval 6–5 cal ka BP, the late-Holocene RCC interval 3.5–2.5 cal ka BP, and the historical RCC interval known as the Little Ice Age (LIA, 1300–1950 AD). Evidence from multiple records indicates wide-ranging impacts of RCCs in the Western Mediterranean region. The three RCC intervals were characterised, however, by contrasting hydrological situations in the Western Mediterranean, with prevailing dry conditions including marked aridification events during the RCC intervals 6–5 and 3.5–2.5 cal ka BP, and prevailing or recurrent wet conditions during the LIA. We examine issues of proxy sensitivity in palaeoecological and geomorphological records and evaluate examples of contrasting geomorphological responses to regional climatic triggers between humid and semi-arid sectors of the Western Mediterranean. Finally, we consider the long-term sensitivity of the region to rapid climate change, the role of threshold changes, and the extent to which this region represents a “fragile” landscape.

Research highlights
► Evidence for Rapid Climate Changes (RCCs) in the Western Mediterranean is reviewed.
► We focus on Holocene RCCs at 6–5 and 3.5–2.5 cal ka BP, and the Little Ice Age (LIA).
► RCC impacts are detected in multiple archives (e.g. marine, lacustrine, fluvial).
► We show contrasting climatic signatures for the earlier RCCs (dry) and LIA (wet).
► Climatic triggers for geomorphological instability during RCCs are evaluated.