Climate Change, Fire and Human Activity Drive Vegetation Change during the Last Eight Millennia in the Xistral Mountains of NW Iberia

Abstract

An 8500-year record of high-resolution pollen, non-pollen palynomorph, microscopic charcoal and selected geochemical data (Ti, Zr and Pb) is presented from an ombrotrophic mire from the Xistral Mountains, Galicia, North-West Iberia. The results suggest that vegetation changes over the last eight millennia are primarily the result of human disturbance, fire and climate change. Climate and fire were the main factors influencing vegetation development during the early to mid-Holocene, including a short-lived decline in forest cover c. 8.2 cal. ka BP. Changes associated with the 4.2 and 2.8 cal. Ka BP events are less well defined. Human impact on vegetation became more pronounced by the late Holocene with major periods of forest disturbance from c. 3.1 cal. ka BP onwards: during the end of Metal Ages, Roman period and culminating in the permanent decline of deciduous forests in the post-Roman period, as agriculture and metallurgy intensified, leading to the creation of a cultural landscape. Climate change appears to become less influential as human activity dominates during the Late Holocene.

Identifying major phases in the use of land, energy and changing landscapes by agrarian societies (7,000 cal BP-Present) in Cantabrian Spain, based on cultural changes and anthropogenic signals

“…Hence, ombrotrophic peat bogs are valuable sedimentary archives for detecting atmospheric pollution in heavy metals and pollen deposition, and thus signals from such archives have been preferential in our research work. The evolution through time of HMC and TTC can be influenced by anthropogenic activities as well as by climatic parameters (Mighall et al, 2023). Hence, both HMC and TTC records were confronted with models of natural vegetation, and with temperature and precipitation indexes in order to refine the extent of climatic and anthropogenic influence on both indicators.…”

“…A wealth of studies on landscape transformations in relation to human activities in Northern Spain have already provided a well-documented landscape evolution storyline throughout the Holocene. Nonetheless, the focal point of such research line is often limited to specific time periods or cultural entities, and considers very specific thematics, such as fire activity (Pérez-Obiol et al, 2016;Carracedo et al, 2018;Uzquiano, 2018), agrarian activity (López-Merino et al, 2010, 2011Fernández Mier et al, 2014), vegetation and environmental reconstitution (Schellekens et al, 2011;Irabien et al, 2015;Pérez-Díaz et al, 2016b), climate evolution (Muñoz-Sobrino et al, 2005;Mighall et al, 2006Mighall et al, , 2023, or human land-use (López-Merino et al, 2014;Pérez-Díaz et al, 2018;González-Álvarez, 2019a,b). All studies acknowledge the difficulty to disentangle anthropogenic influences on landscape changes from natural ones (Mighall et al, 2023).…”