The Holocene British and Irish Ancient Forest Fossil Beetle Fauna: Implications for Forest History, Biodiversity and Faunal Colonisation
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ARTICLE IN PRESS Quaternary Science Reviews 25 (2006) 1755–1789 The Holocene British and Irish ancient forest fossil beetle fauna: implications for forest history, biodiversity and faunal colonisation Nicki J. Whitehouse Palaeoecology Centre, School of Archaeology and Palaeoecology, Queen’s University Belfast, Belfast BT7 1NN, Northern Ireland, UK Received 15 June 2004; accepted 10 August 2005 Abstract This paper presents a new review of our knowledge of the ancient forest beetle fauna from Holocene archaeological and palaeoecological sites in Great Britain and Ireland. It examines the colonisation, dispersal and decline of beetle species, highlighting the scale and nature of human activities in the shaping of the landscape of the British Isles. In particular, the paper discusses effects upon the insect fauna, and examines in detail the fossil record from the Humberhead Levels, eastern England. It discusses the local extirpation of up to 40 species in Britain and 15 species in Ireland. An evaluation of the timing of extirpations is made, suggesting that many species in Britain disappear from the fossil record between ca 3000 and 1000 cal BC (ca 5000–3000 cal BP), although some taxa may well have survived until considerably later. In Ireland, there are two distinct trends, with a group of species which seem to be absent after ca 2000 cal BC (ca 4000 cal BP) and a further group which survives until at least as late as the medieval period. The final clearance of the Irish landscape over the last few hundred years was so dramatic, however, that some species which are not especially unusual in a British context were decimated. Reasons behind the extirpation of taxa are examined in detail, and include a combination of forest clearance and human activities, isolation of populations, lack of temporal continuity of habitats, edaphic and competition factors affecting distribution of host trees (particularly pine), lack of forest fires and a decline in open forest systems. The role of climate change in extirpations is also evaluated. Consideration is given to the significance of these specialised ancient forest inhabitants in Ireland in the absence of an early Holocene land-bridge which suggests that colonisation was aided by other mechanisms, such as human activities and wood rafting. Finally, the paper discusses the Continental origins of the British and Irish fauna and its hosts and the role played by European glacial refugia. r 2006 Elsevier Ltd. All rights reserved. 1. Introduction seen perhaps most dramatically in areas such as New Zealand, where the environmental impact of settlement It is observable that not only the moose and the wolf caused faunal extirpation, dramatic changes in erosion disappear before the civilised man, but even many rates, sedimentation and deforestation (e.g. McGlone, species of insects, such as the black fly and the almost 1983; Martin, 1984; McGlone and Wilmshurst, 1999). In microscopic ‘‘no-see-em’’. How imperfect a notion have contrast, the European lands from which many of the we commonly of what was the actual condition of the settlers originated had already been significantly modified place where we dwell, three centuries ago! Henry David and shaped by millennia of cultural activities, but where Thoreau, January 29, 1856 (Homan, 1991, p. 132). the effects of human impact had had no less of a dramatic Henry Thoreau’s comments relate to some of the impact—albeit over a more protracted period of time. enormous changes to the American flora and fauna which The study of sub-fossil beetles has highlighted the scale arose within a few centuries of the arrival of Europeans. of these environmental impacts in Europe, particularly The palaeoecological record covering this period highlights over the last 5000 years of the Holocene (Buckland and the dramatic environmental impact of such settlers (e.g. Coope, 1991). Transitions from forested to cleared land- Baker et al., 1996; Schwert, 1996; Bradbury et al., 2004), scape (termed ‘‘culture steppe’’ by Hammond (1974)) have been observed from several sites (e.g. Girling, 1985, 1989; E-mail address: [email protected]. Dinnin, 1997). Much of this record has been obtained via 0277-3791/$ - see front matter r 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.quascirev.2006.01.010 ARTICLE IN PRESS 1756 N.J. Whitehouse / Quaternary Science Reviews 25 (2006) 1755–1789 fossil beetles from archaeological investigations, from both geographical focus of the paper is Great Britain and rural and urban archaeological sites (e.g. Girling, 1976, Ireland, where there has been a long tradition of 1979; Hall and Kenward, 1980; Robinson, 1991, 2000; palaeoentomology (particularly in the former rather than Kenward and Hall, 1995; Hall et al., 2003). There have also the latter) and a correspondingly good data set, although been palaeoecological studies which have examined ‘‘nat- reference is also made to research carried out elsewhere. ural’’ deposits, indirectly associated with archaeological Figs. 1 and 2 show the location of sites discussed. features, but which carry a record of human impact on the Coleoptera nomenclature follows Lucht (1987), whilst landscape. The anaerobic conditions ensure excellent plant nomenclature follows Stace (1991). Information preservation of fossils whilst the often rapid build-up of on insect biology has been obtained from the entomo- deposits provide good temporal resolution. Floodplain logical database BUGS (Buckland et al., 1997, www. deposits, for instance, are immensely valuable, as they bugs2000.org), whilst distributional information has been provide records of fluvial histories, floodplain evolution largely obtained by a search through specialised catalogues and change, vegetation composition and structure as well housed in the Royal Entomological Society’s library, as the nature and scale of human impact (e.g. Osborne, London. Where necessary, reference is made to the current 1988, 1995; Dinnin, 1997; Andrieu-Ponel et al., 2000; threatened status of some of the beetles discussed. These Plunkett et al., 2003; Smith and Howard, 2004). Bogs and are species which are included in the Nature Conservancy fens are also rich sources of fossil insect assemblages, Council’s British Red Data Books: 2, Insects (Shirt, 1987). although fen peats tend to be richer in insect remains than This is a comprehensive statement on the status of most acid peats (e.g. Buckland, 1979; Klinger et al., 1990; Elias, threatened insects in Great Britain. The book contains 1994; Roper, 1996; Whitehouse, 1997a, 2004; Ponel et al., three major categories based upon degrees of threat, RDB 2001; Marra, 2003). Results of such investigations highlight (Red Data Book) 1, 2 and 3 (respectively, endangered the enormous changes effected upon the British and Irish vulnerable and rare). A further classification of Notable faunas, particularly since the onset of agriculture. More- species (A and B) (Hyman, 1992, 1994) is also used. over, they also provide an insight into the rapid colonisa- Notable A species are those which do not fall within RDB tion and expansion of these islands by insects as the ice categories but which are none-the-less uncommon and are sheets retreated. thought to occur in 30 or fewer 10 km2 of the National This paper presents a new contribution towards our Grid, whilst Notable B taxa are those which are thought to understanding of the colonisation, dispersal and decline of insect species and what this can tell us about the nature and role of human activities in the shaping of the European landscape and their effects upon the insect fauna. In particular, the contraction of old forest communities and species (Urwaldtiere) is examined in detail. This contribu- tion augments discussions originally highlighted by Os- borne (1965, 1997), Buckland and Kenward (1973), Buckland (1979), Girling (1982, 1985), Whitehouse (1997a, b), Dinnin and Sadler (1999) and Smith and Gransmoor Humberhead Levels Whitehouse (2005), and brings together information Wood Hall published in a wide variety of sources which will be of Chelford Dimlington interest not only to palaeoecologists but also researchers Bole Ings interested in Holocene forest history and ecology. It differs from previous accounts by considering previously pub- Rodbaston Wilsford lished (Coope et al., 1979; Reilly, 1996, 2003; Caseldine et West Bromich Lea Marston al., 2001; Whitehouse, in press) and unpublished Irish research (e.g. Rogers, 2004). It also discusses in detail the Upton Warren biology of saproxylic species (species where ‘‘the immature Dorney stages develop in some part of the wood-decay succession Runnymede or on the products of it’’, Alexander, 2002, p. 10) and Sweet Track Hampstead causes for the dramatic changes seen amongst the fauna, Heath including climatic factors and their wider significance. It Hollywell Coobe also provides distributional and habitat information of individual species which have not previously been pub- lished and adds to the last major review of these species 0 100 200 km undertaken by Buckland (1979). Finally, the paper addresses issues concerned with the mechanisms behind the initial colonisation of insect biota, particularly to Fig. 1. Map of England and Wales, showing location of sites discussed in Ireland, and considers the Continental origins of taxa. The the text. ARTICLE IN PRESS N.J. Whitehouse / Quaternary Science Reviews 25 (2006) 1755–1789 1757 appropriate to report these as cal BC dates in the same manner. Deer Park Farms 2. The ancient forest fossil beetle record Sluggan Bog Ballymacombs Belfast More 2.1. The development of Urwald and the expansion of the Strangford beetle fauna Aghnadarragh Lough The Lateglacial period (ca 13,000–10,000 BP) is impor- Drumurcher tant in any consideration of the beetle fauna of the present interglacial. Hammond (1974) suggests that as much as half Corlea of the present-day fauna had already established itself Dublin before major afforestation. Investigations by Coope (1979) indicate that thermophilous species arrived extremely rapidly during the early phases of warming. Southern Derryville parts of Britain acted as a glacial refuge for at least some cold-adapted species since these areas were not covered by ice sheets.