Roy van Beek

Many stream valleys in Northwestern Europe were once peat-filled during the Holocene. Nonetheless, they are often not considered as peat valleys in restoration projects, as they are now covered by thick clastic deposits. This sediment influx is often attributed to past deforestation and intensification of agriculture on adjacent hill slopes. However, this explanation fails in lowlands such as the Netherlands. How the clastic material formed in those stream valleys is still unclear. This study aims to determine the origin of thick humic sand covers in formerly peat-rich stream valleys. Two stream valleys in the sandy southern Netherlands were studied, the Keersop and the Kleine Dommel. The formation of the humic sand covers was studied by mapping the soils and subsurface lithology, luminescence dating and a review of archaeological and historical information. Our interdisciplinary research design has revealed direct human controls on historical floodplain transformations from peat-dominated to clastic-dominated in both valleys. The results show that the humic sand covers display many similarities with other Plaggic Anthrosols in the region, which developed after fertilisation of arable lands since the Middle Ages. Both contain humic sand, traces of charcoal and ceramics, and both can contain light-coloured sand inclusions. Our datings show the soils in the Kleine Dommel valley were anthropogenically raised during the late 17th or early 18th centuries. We argue that artificial raising of stream valleys with sands was a common practice in the southern Netherlands, intended to support agriculture on the existing peaty soils by improving their bearing capacity and drainage. This identified human-induced lowland floodplain transformation from peat-dominated to clastic-dominated underlines that these past human alterations should be considered when restoring stream valley ecosystems.

Despite repeated calls for action from various sources, peatland archaeological sites continue to deteriorate; the passive strategy of preservation in situ is failing. Here, the authors consider four challenges to peatland preservation—physical degradation, mapping and monitoring of sites, communication, and policy frameworks—with climate change ultimately causing further problems. Drawing on positive policy developments in England, they argue that advocacy for peatland archaeology needs to be louder and clearer: archaeology must become an integral consideration in all climate-change mitigation and land-use planning, rather than an afterthought, if the fragile heritage of European peatlands is to be preserved.

Integration of natural and cultural resource management is urgently needed to combat the effects of climate change. Scientists must contend with how human-induced climate change and rapid population expansion are fundamentally reworking densely inhabited coastal zones. We propose that a merger of archaeology, environmental science, and land management policy—different yet intertwined domains—is needed to address dramatic losses to biocultural resources that comprise coupled cultural-natural systems. We demonstrate the urgency of such approaches through analyses of coastal archaeological regions within the U.S. Atlantic and Gulf coasts where sea level rise is a primary threat, and we extend our findings globally through an assessment of primary risk factors and forecasts for archaeological sites in the Netherlands, Peru, and Oceania. Results show that across the U.S. Gulf Coast and in Oceania, where little hard infrastructure is in place to protect archaeological sites, hundreds of low-lying coastal sites will be lost under future climate scenarios. In other coasts, like that of the Rhine-Meuse Delta (the Netherlands), risks range from erosion caused by periods of flooding to the degradation of wetland sites caused by extreme droughts. In coastal Peru, population pressures pose the primary risk to archaeological sites through rapid agro-industrial growth, urban expansion, and El Niño climate variability. Across all risks, we propose that management strategies to mitigate losses to biocultural resources must be approached as a restoration process of linked sociocultural and physical environmental systems.

Dikes are among the most significant ancient human-made earthworks for flood control, land reclamation, and water management for millennia. However, determining the age of dike construction and development based on traditional dating methods (e.g., historical documents, archaeological find materials, and radiocarbon dating), is challenging, due to the paucity of materials and historical records. Luminescence dating may provide an alternative as it uses ubiquitous quartz or feldspar minerals to directly determine the burial age of sediments. In this study, we applied quartz optically stimulated luminescence (OSL) and feldspar single-grain post-infrared infrared stimulated luminescence (pIRIR) dating on two dikes: the Waal dike (near Wolferen-Sprok) in the Netherlands and the Scheldt dike (near Bornem) in Belgium. Our results confirm that luminescence dating provides reliable age estimates, consistent with other independent proxy data such as radiocarbon dating, archaeological artifacts, and historical evidence, and may refine site chronologies. Based on the age results, the history of dike construction and evolution was reconstructed. Additionally, the well-reset OSL signals for dike-related sediments suggest that fresh flood deposits were used for construction. This study highlights the potential of luminescence dating as a robust tool for reconstructing the history of dike construction and understanding ancient engineering.

Plaggic anthrosols demonstrate the significant and widespread influence of agriculture on the landscape of northern Europe and testify to increased land-use intensity over the last millennium. However, a lack of established chronologic methods to interrogate these soils has hindered research on their formation history, so the timing and process of plaggic anthrosol development remain poorly quantified. Recently, luminescence dating methods have emerged as a tool for tracing the past movement of grains, including within the soil column. This study combines two primary luminescence methods – single-grain feldspar infrared stimulated luminescence (IRSL) along with post-infrared infrared stimulated luminescence (pIRIR) measurements and small-aliquot (or multi-grain) quartz optically stimulated luminescence (OSL) – to reconstruct the formation of a plaggic anthrosol at Braakmankamp (eastern Netherlands). Toward this aim, we present a new method to identify well-bleached single grains of feldspar using the ratio of the grain's IRSL and pIRIR signals as a filter. The results provide both methodological and applied archaeological insights. Both small-aliquot quartz OSL and single-grain feldspar pIRIR ages yield reliable ages for plaggen deposits when the new filtering approach is used to remove poorly bleached feldspar grains from the analysis. Single-grain pIRIR feldspar has the added benefit of revealing complex soil formation histories for naturally bioturbated deposits, including those at the base of the plaggen layer. Augmenting this information with conventional quartz OSL dating builds confidence in the geo-chronologic record and allows us to reconstruct the timing and processes of plaggic anthrosol formation in Braakmankamp. According to the luminescence dating results, land clearance occurred around 900–1000 years ago, and accumulation of plaggen material began around 700–800 years ago. The average accumulation rate of plaggen material is estimated at ∼ 1.1 mm yr⁻¹.