Willy Tegel

Old World megadroughts and pluvials during the Common Era

An atlas of megadroughts in Europe and in the Mediterranean Basin during the Common Era provides insights into climate variability. Climate model projections suggest widespread drying in the Mediterranean Basin and wetting in Fennoscandia in the coming decades largely as a consequence of greenhouse gas forcing of climate. To place these and other “Old World” climate projections into historical perspective based on more complete estimates of natural hydroclimatic variability, we have developed the “Old World Drought Atlas” (OWDA), a set of year-to-year maps of tree-ring reconstructed summer wetness and dryness over Europe and the Mediterranean Basin during the Common Era. The OWDA matches historical accounts of severe drought and wetness with a spatial completeness not previously available. In addition, megadroughts reconstructed over north-central Europe in the 11th and mid-15th centuries reinforce other evidence from North America and Asia that droughts were more severe, extensive, and prolonged over Northern Hemisphere land areas before the 20th century, with an inadequate understanding of their causes. The OWDA provides new data to determine the causes of Old World drought and wetness and attribute past climate variability to forced and/or internal variability.

Climate Change during and after the Roman Empire: Reconstructing the Past from Scientific and Historical Evidence

Growing scientific evidence from modern climate science is loaded with implications for the environmental history of the Roman Empire and its successor societies. The written and archaeological evidence, although richer than commonly realized, is unevenly distributed over time and space. A first synthesis of what the written records and multiple natural archives (multi-proxy data) indicate about climate change and variability across western Eurasia from c. 100 b.c. to 800 a.d. confirms that the Roman Empire rose during a period of stable and favorable climatic conditions, which deteriorated during the Empires third-century crisis. A second, briefer period of favorable conditions coincided with the Empires recovery in the fourth century; regional differences in climate conditions parallel the diverging fates of the eastern and western Empires in subsequent centuries. Climate conditions beyond the Empires boundaries also played an important role by affecting food production in the Nile valley, and by encouraging two major migrations and invasions of pastoral peoples from Central Asia.

Filling the Eastern European gap in millennium-long temperature reconstructions.

Tree ring–based temperature reconstructions form the scientific backbone of the current global change debate. Although some European records extend into medieval times, high-resolution, long-term, regional-scale paleoclimatic evidence is missing for the eastern part of the continent. Here we compile 545 samples of living trees and historical timbers from the greater Tatra region to reconstruct interannual to centennial-long variations in Eastern European May–June temperature back to 1040 AD. Recent anthropogenic warming exceeds the range of past natural climate variability. Increased plague outbreaks and political conflicts, as well as decreased settlement activities, coincided with temperature depressions. The Black Death in the mid-14th century, the Thirty Years War in the early 17th century, and the French Invasion of Russia in the early 19th century all occurred during the coldest episodes of the last millennium. A comparison with summer temperature reconstructions from Scandinavia, the Alps, and the Pyrenees emphasizes the seasonal and spatial specificity of our results, questioning those large-scale reconstructions that simply average individual sites.

Placing unprecedented recent fir growth in a European-wide and Holocene-long context

Forest decline played a pivotal role in motivating Europes political focus on sustainability around 35 years ago. Silver fir (Abies alba) exhibited a particularly severe dieback in the mid-1970s, but disentangling biotic from abiotic drivers remained challenging because both spatial and temporal data were lacking. Here, we analyze 14 136 samples from living trees and historical timbers, together with 356 pollen records, to evaluate recent fir growth from a continent-wide and Holocene-long perspective. Land use and climate change influenced forest growth over the past millennium, whereas anthropogenic emissions of acidic sulfates and nitrates became important after about 1850. Pollution control since the 1980s, together with a warmer but not drier climate, has facilitated an unprecedented surge in productivity across Central European fir stands. Restricted fir distribution prior to the Mesolithic and again in the Modern Era, separated by a peak in abundance during the Bronze Age, is indicative of the long-term interplay of changing temperatures, shifts in the hydrological cycle, and human impacts that have shaped forest structure and productivity.

Early Neolithic Water Wells Reveal the World's Oldest Wood Architecture

The European Neolithization ∼6000−4000 BC represents a pivotal change in human history when farming spread and the mobile style of life of the hunter-foragers was superseded by the agrarian culture. Permanent settlement structures and agricultural production systems required fundamental innovations in technology, subsistence, and resource utilization. Motivation, course, and timing of this transformation, however, remain debatable. Here we present annually resolved and absolutely dated dendroarchaeological information from four wooden water wells of the early Neolithic period that were excavated in Eastern Germany. A total of 151 oak timbers preserved in a waterlogged environment were dated between 5469 and 5098 BC and reveal unexpectedly refined carpentry skills. The recently discovered water wells enable for the first time a detailed insight into the earliest wood architecture and display the technological capabilities of humans ∼7000 years ago. The timbered well constructions made of old oak trees feature an unopened tree-ring archive from which annually resolved and absolutely dated environmental data can be culled. Our results question the principle of continuous evolutionary development in prehistoric technology, and contradict the common belief that metal was necessary for complex timber constructions. Early Neolithic craftsmanship now suggests that the first farmers were also the first carpenters.

Potential and limitations of Burgundy truffle cultivation

Burgundy truffles (Tuber aestivum syn. Tuber uncinatum) are the highly prized fruit bodies of subterranean fungi always occurring in ectomycorrhizal symbiosis with host plants. Successful cultivation can be achieved through artificial mycorrhization and outplanting of mostly oaks and hazel on suitable terrain. Here, we review ecological requirements, the influence of environmental factors, and the importance of molecular techniques for a successful cultivation of T. aestivum across Europe. The historical background and current knowledge of T. aestivum cultivation are discussed in light of its socioeconomic relevance.

Tree-Ring Amplification of the Early Nineteenth-Century Summer Cooling in Central Europe

Annually resolved and absolutely dated tree-ring chronologies are the most important proxy archives to reconstruct climate variability over centuries to millennia. However, the suitability of tree- ...

Evaluating the wood anatomical and dendroecological potential of arctic dwarf shrub communities

Supplementing broader-scale dendroecological approaches with high-resolution wood anatomical analyses constitutes a useful technique to assess spatiotemporal patterns of climate-induced growth responses in circumpolar tundra vegetation. A systematic evaluation of dendrochronological and wood anatomical features in arctic dwarf shrubs is, however, still missing. Here, we report on nearly thousand samples from ten major dwarf shrub species that were collected at 30 plot-sites around 70°N and 22°W in coastal East Greenland. Morphological root and stem characteristics, together with intra-annual anatomical variations are outlined and the potential and limitation of ring counting is stressed. This study further demonstrates the possibility to gain annually resolved insight on past dry matter production and carbon allocation in arctic (and alpine) environments well beyond northern (and upper) treelines, where vegetation growth is particularly sensitive to environmental change.

Timber Logging in Central Siberia is the Main Source for Recent Arctic Driftwood

Abstract Recent findings indicated spruce from North America and larch from eastern Siberia to be the dominating tree species of Arctic driftwood throughout the Holocene. However, changes in source region forest and river characteristics, as well as ocean current dynamics and sea ice extent likely influence its spatiotemporal composition. Here, we present 2556 driftwood samples from Greenland, Iceland, Svalbard, and the Faroe Islands. A total of 498 out of 969 Pinus sylvestris ring width series were cross-dated at the catchment level against a network of Eurasian boreal reference chronologies. The central Siberian Yenisei and Angara Rivers account for 91% of all dated pines, with their outermost rings dating between 1804 and 1999. Intensified logging and timber rafting along the Yenisei and Angara in the mid-20th century, together with high discharge rates, explain the vast quantity of material from this region and its temporal peak ca. 1960. Based on the combined application of wood-anatomical and dendrochronological techniques on a well-replicated data set, our results question the assumption that Arctic driftwood mainly consists of millennial-old larch and spruce. Nevertheless, data from other species and regions, together with longer boreal reference chronologies, are needed for generating reliable proxy archives at the interface of marine and terrestrial environments.

Digitizing Historical Plague

TO THE EDITOR– Outbreaks of bubonic plague initiated by the flea-borne bacterium Yersinia pestis have repeatedly afflicted the Old World since the onset of the ‘Justinian Plague’ in 541 AD [1]. The second European pandemic, the ‘Black Death’ rapidly killed around half of the population during 1347–1353 AD. Both pandemics then persisted with recurrent local outbreaks over several centuries. The reason for the eventual cessation of each pandemic remains mysterious [1], particularly in light of continued activity in Asia [2] where the infection is enzootic in its natural rodent hosts [3]. Socio-political influences have often compounded the complexity of plague ecology, likely increasing the spillover of infection into human populations [1–3]. The threat from the plague bacillus, which still induces several thousand human cases annually, may well increase under projected climate change [1] – and, ominously, within the context of bioterrorism [4]. Knowledge of plague ecology, epidemiology, and pathophysiology is,