Representing regions in dendrochronological data

An international team of archaeologists, historians, and scientists has used felling-date data to conduct an investigation into medieval and early modern building activity.

Dendrochronology is a method of dating wood by analysing the annual growth patterns present in tree rings, and then comparing the results with tree ring samples with known dates to reveal the exact year in which the rings were formed. When the outermost and youngest (‘waney edge’) ring is present, dendrochronologists can even determine the precise year in which a tree was felled. The technique can help date individual buildings (see CA 334 and 358), but now an international team of 58 archaeologists, historians, geographers, and environmental scientists has used felling-date data to conduct a larger-scale investigation into medieval and early modern building activity rates as indicators of social, demographic, and economic change at both regional and Europe-wide scales.

The researchers collected 54,045 felling dates from pieces of timber – such as roof trusses and ceiling joints – used in European building construction between 1250 and 1699. They found that building activity rates broadly mapped periods of socio-economic significance: there were generally high levels around the mid to late 13th century, followed by a decline from c.1295, which intensified c.1340 (corresponding to the so-called ‘Late Medieval Crisis’ of c.1300-1415, when much of Europe was hit by famine, disease, war, and schism). After this, building rates recovered inconsistently, only reaching 13th-century levels again at the end of the 15th century, and peaking in the mid-16th century. There was then another decline towards the end of that century and into the 17th, with the sharpest drops coinciding with one of pre-industrial Europe’s bloodiest conflicts, the Thirty Years’ War (1618-1648), followed by another building boom in the late 17th century.

Changes in European building activity (13th to 17th centuries). Annual felling dates are presented as index values (in green) and distinct phases are highlighted by a black line. Image: Ljungqvist et al.

These results, published in Frontiers in Ecology and Evolution (Ljungqvist, Seim et al;, expand upon a 2018 study by Ljungqvist et al. (published in the Journal of Archaeological Science:, which analysed dendrochronological data from across the former Holy Roman Empire and France. The 2018 researchers found that reductions in building activity corresponded with higher numbers of plague outbreaks and increased grain prices, highlighting the significance of dendrochronological data as a source of information about periods of societal crisis and prosperity. In the more recent study, though, the team has expanded the area under survey, using geostatistical analysis to investigate and compare building activity rates across Europe’s multiple regions.

The researchers grouped their dendrochronological data into seven clusters with relative geographic, cultural, and economic unity: the British Isles, the Nordic countries, France, the Benelux countries, northern central Europe, southern central Europe, and Switzerland. Geographic information system (GIS) analysis was then used to analyse the building activity rates, revealing significant variation across the regions. The largest disparities were linked to the timing and duration of the ‘Late Medieval Crisis’ in different areas, and to the varied impacts of the Thirty Years’ War. That said, the team still found strong correlations between building activity in the British Isles and southern central Europe, and between building rates in both northern and southern central Europe.

For the British Isles, the researchers found no indication of a building activity decline in the early 14th century – as opposed to France, the Benelux countries, and northern central Europe. Moreover, the late 15th-century building boom recorded for France, the Benelux countries, and central Europe was found to be absent for the British Isles, Switzerland, and the Nordic countries. Similarly, the distinctive increase in building activity reported for the Benelux countries, northern central Europe, and Switzerland in the mid-16th century was not mirrored in the British Isles (though building activity there did increase in the 1530s). Nor did building activity there decline during the Thirty Years’ War (which never reached the British Isles), as it did in central and eastern Germany and in southern central Europe, where there were areas of high population loss.

While the societal, economic, and demographic changes outlined in the study have previously been identified through traditional historical and archaeological analyses, this dendrochronological perspective contributes new data on European building-activity rates, for which there are few written sources. This was found to correlate positively with evidence of mining activity, and negatively with the price of grain, confirming that dendrochronological data can be considered a useful source for exploring societal and demographic changes at macro-historical and regional levels.