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The activity of macrofauna on the sea floor is since long known to mediate deposition and erosion of sediment, but so far most studies addressed this effect at a local scale. In the present paper, the contribution of the observed macrofauna distribution (exemplified by a bivalve, the bean-like tellin Fabulina fabula, formerly known as Tellina fabula) on large-scale sediment transport in the southern North Sea is investigated by means of a model study. Macrofauna effects are considered with respect to the critical bed shear stress and erodibility, which are two important factors that control the resuspension rate. Simulation results for a typical winter month revealed for the first time that the suspended sediment concentration (SSC) is increased not only locally but beyond the inhabited zones. This alteration is not confined to near-bed zones but can be observed throughout the entire water column, especially during storm events. These effects are most prominent in the fine silt fraction, coarser and finer fractions are less affected. For a selected storm event in February 2010, we explain the counter-intuitive decrease in near-bed SSC in some areas with a high macrofauna abundance compared to a simulation excluding such macrofauna: A high macrofauna-induced entrainment rate leads to rapid exhaustion of available sediments at the bed in the model and consequently limits the near-bed SSC.

Inferred European Holocene population size exhibits large fluctuations, particularly around the onset of farming. We attempt to find explanations for these fluctuations by employing the concept of cycling, especially that of the Adaptive Cycle. We base our analysis on chronologically and chorologically highly resolved ceramic and site data from the Linear Pottery culture (Germ. Linearbandkermik ) of the early Neolithic of southwestern Central Europe. Typological seriation with dendrochronological anchor dates provides the age model for these data. Ceramic motifs are analysed with respect to the temporally changing diversity in decoration. The temporal sequence of major decoration motifs is interpreted as an indicator of social diversity: when stylistic diversity is low, social diversity is low and vice versa. The sequence of secondary decoration motifs is interpreted in terms of individual lineage emphasis: when this diversity is low, there is strong emphasis on individual lineage and vice versa. The diversity time series are complemented by a relative population size indicator derived from the count of occupational features. Diversity and population size share a shape that is typical for (part of) an Adaptive Cycle, and they differ in their positioning on the time axis — they are time-lagged. By relating the different curves to the (metaphorical) stages of the Adaptive Cycle, we find that these cycles progress at non-identical speed in different aspects of a social system. By relating the social dynamics to well-dated and highly resolved climate fluctuation records, we find evidence that severe climate excursions shaped the location of tipping points in the social system and that these social tipping points precede inferred population decline by several generations.

Highlights: • 18 southern European charcoal records document 16,000 years of fire regime changes. • Since the Neolithic, land uses have artificially maintained high fire frequencies. • Human-induced decreases in forest cover led to a reduction in the biomass burned. • Human-modified landscapes affected ecological processes more meaningly than expected. Abstract: Variability in fire regime at the continental scale has primarily been attributed to climate change, often overshadowing the widely potential impact of human activities. However, human ignition modifies the rhythm of fire episodes occurrence (fire frequency), whereas land use alters vegetation composition and fuel load, and thus the amount of biomass burned. It is unclear, however, whether and how humans have exercised a significant influence over fire regimes at continental and millennial scales. Based on sedimentary charcoal records, we use new alternative estimate of fire frequency and biomass burned for the last 16000 years (here after 16 ky) that we evaluate with outputs from climate, vegetation, land use and population models. We find that pronounced regional-scale land use changes in southern Europe at the beginning of the Neolithic (8–6 ky), during the Bronze Age (5–4 ky) and the medieval period (1 ky) caused a doubling of fire frequency compared to the Holocene average (the last 11.5 ky). Despite anthropogenic influences, southern European biomass burned decreased from 7 ky, which is in line both with changes in orbital parameters leading climate cooling and also reductions in biomass availability because of land use. Our study underscores the role of elevation-dependent parameters, and particularly biomass and land management, as major drivers of fire regime variability. Results attest a determinant anthropogenic driving-force on fire regime and a decrease in fire-carbon emissions since 7 ky in Southern Europe.

Was the spread of agropastoralism from the Fertile Crescent throughout Europe influenced by extreme climate events, or was it independent of climate? We here generate idealized climate events using palaeoclimate records. In a mathematical model of regional sociocultural development, these events disturb the subsistence base of simulated forager and farmer societies. We evaluate the regional simulated transition timings and durations against a published large set of radiocarbon dates for western Eurasia; the model is able to realistically hindcast much of the inhomogeneous space-time evolution of regional Neolithic transitions. Our study shows that the consideration of climate events improves the simulation of typical lags between cultural complexes, but that the overall difference to a model without climate events is not significant. Climate events may not have been as important for early sociocultural dynamics as endogenous factors., Revised version submitted to the Journal of Archaeological Science, special issue on The World Reshaped: impacts of the Neolithic transition. 10 pages, 4 figures, 1 table + supplementary material