peatlands 1 taitto.indd - International Peat Society

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Figure 3: The Bargerveen in the Netherlands, showing the Subboreal-Subatlantic climate transition (indicated). The correlation of increased 14 C (which means solar infl uence), wet shift in peat bogs and climatic detoriation is also observed for the strong 14 C excursions, observed during the so-called Little Ice Age (ca. 1600 AD; see Figure 2). In addition, the increased production of cosmogenic isotopes Figure 4: Variations in the natural 14 C content (see fi gure 2), zoomed in for 1000-500 BC. Also shown is a selection of botanical data from Engbertsdijksveen, the Netherlands. The sharp rise in the 14 C signal (a solar proxy) coincides with a climatic detoriation, as observed in a shift in Sphagnum species. 48 PEATLANDS International 1/2006 ( 14 C, but also 10 Be) appears to be associated with cooler climate throughout the complete Holocene. It is important to note that the observed teleconnections are an indication that “solar forcing” of climate change plays a more important role than previously thought. The mechanism is still not understood, however. To extract palaeoclimatic information from peat bogs, a variety of research programs are implemented. As a good example, we mention the EC-funded project Accrotelm (Abrupt Climate Changes Recorded Over The European Land Mass). For detailed information we refer to www. glos.ac.uk/accrotelm. Peat bogs and cultural finds In the extensive peat bogs of Northwestern Europe, archaeological fi nds shed light on past cultures. Such fi nds mostly took place during the era of peat cutting. From the 17th - early 20th century, peat was a major source of energy in Northwestern Europe. A fi ne example of an archaeological fi nd is shown in fi gure 5: a wooden bog road from the Neolithic (ca. 2100 BC), found in the peatlands of Nieuw Dordrecht, province of Drenthe, the Netherlands. A mystery is that the road does not lead anywhere; the construction was stopped for some reason. Wooden wheels, shoes, stone tools, pottery, ornaments and even unique remains of a temple (Barger-Oosterveld) have surfaced from the peat during the cutting era, illuminating cultures of the past from the Stone Age, Bronze Age and Iron Age. Bog bodies The most dramatic fi nds are people - the well known bog bodies. These bodies are known from the peats of (mainly) Ireland, England, Germany, the Netherlands and Denmark. Unfortunately, many bog bodies did not survive their discovery very long. Quite a few were reburied; others were destroyed (or even powdered into a medicine: “mumia”). But several bodies did fi nd their way into museums. Some bog bodies were found in an excellent state of preservation, like the famous Tollund Man in Denmark. Others, like the Yde girl (fi gure 6a), were damaged during the peat cutting and decayed partly after their discovery, before conservation measures could be applied. The Yde girl is the most famous bog body of the Netherlands, perhaps because her head has been reconstructed (Figure 6b). The body was found in 1897 near the village of Yde (province of Drenthe, the Netherlands). She obviously died through strangulation with a woollen band, still visible around her neck. Her age is established as 16 years old. Establishing the age of bog bodies was for a long time a major problem, as most of them came to light unaccompanied by objects that could be dated on the basis of typological evidence. In addition, 14 C dating is hampered by the prolonged “chemical treatment” of the samples by the peat acids. Recently, a large series of bog bodies were 14 C dated by systematic analysis of materials like clothing (fur, textile), skin, leather (shoes), hair,
Figure 5: Bog road (consisting of trees) constructed in a peat bog ca. 4100 years ago near Nieuw Dordrecht, the Netherlands. wood and bone (when available) using the equipment shown in fi gure 1. It appears that most bog bodies date from the Late Iron Age / Roman period (ca. 2nd century BC - 4th century AD). For example, Radiocarbon measurements indicate that the Yde girl shown in fi gure 6, dates between 40 BC and 50 AD. Final remarks Peat bogs are powerful archives of the past. Their botanical remains form a record of the ecological circumstances like climate. In addition, intriguing prehistoric cultural evidence came to light during the peat cutting era. This illustrates the old saying that “in order to understand the present one needs to understand the past”. The most spectacular archaeological fi nds are the bog bodies, several of which had been executed (like the Yde girl, but also Tollund man and others), as proven by strangulation ropes. Most archaeologists think that these bodies are offerings, but this remains speculation. It is certain, however, that the peat bogs did function as places to offer. There is no other explanation for the occurrence of many pots with valuable amber beads (sometimes thousands), and Nordic bronze musical instruments (lures) which are found in pairs in the peat and which must have been extremely valuable for prehistoric man. In terms of the palaeoclimate, peat bogs suggest that past variations in the activity of the sun have been important contributing factors for climate change. This issue - “solar forcing” of climate change - is now back on the scientifi c agenda, in addition to the more generally recognised “CO 2 (greenhouse) forcing”. It is obviously crucial that the role of “solar forcing” be taken into account in evaluating the anthropogenic contribution to climate change of our planet. � Selected literature M.Blaauw, B.van Geel, and J.van der Plicht, 2004. Solar forcing of climatic change during the mid-Holocene: indications from raised bogs in the Netherlands. The Holocene 14, 35-44. B.van Geel, J.van der Plicht, M.R.Kilian, E.R.Klaver, J.H.M.Kouwenberg, H.Renssen, I. Reynaud- Farrera, and H.T.Waterbolk, 1998. The sharp rise of 14 C ca. 800 cal BC: possible causes, related climatic connections and the impact on human environments. Radiocarbon 40, 535-550. R.A. Kerr, 2001. A variable sun paces millennial climate. Science 294, 1431-1433. J.van der Plicht, W.A.B.van der Sanden, A.T.Aerts and H.J.Streurman, 2004. Dating Bog Bodies by 14 C-AMS. Journal of Archaeological Science 31, 471-491. J.D. Haigh, 2001. Climate variability and the infl uence of the sun. Nature 294, 2109-2111. J. van der Plicht Center for Isotope Research Groningen University Groningen, the Netherlands and Faculty of Archaeology Leiden University Leiden, the Netherlands e-mail: j.van.der.plicht@rug.nl Figure 6: a) Yde Girl, the bog body of a 16 year old girl found in 1897 near the village of Yde, the Netherlands. Note the woollen band used to strangle the girl, visible around her neck. b) reconstruction of the head of the Yde girl. 49
Page 1 and 2: PEATLANDS International Peatlands a
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Page 47: Trees as calendars The varying 14 C
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