Fossil insect remains as indicators of the primeval forest; a modern analogue approach.
Lead Research Organisation:
Queen's University Belfast
Department Name: Geography Archaeology and Palaeoecology
Abstract
Native woodland is a scarce resource of high cultural, scientific and nature conservation importance throughout Europe. In a recently published hypothesis, a Danish woodland ecologist, Frans Vera, has argued that the current European management policy towards 'closed' canopy woodland is affecting the continued viability of specialised plants and animals of the forest. Many sites are highly valued for these specialised species. Vera argues that large herbivores played an important role in maintaining substantial open areas in the 'wildwood' of primeval Europe, so that the forest, far from being closed, was in fact quite open. This is contrast to the established thinking that the 'wildwood' was a closed canopy forest and so management of ancient woodland sites, which aims to maintain and/or restore sites to their natural ecological state, has been geared towards this assumption. The implications of Vera's argument are clear: if he is correct, we have been managing these precious sites (and their species) in an incorrect manner and are thus are danger of compromising their future. In order to establish whether the 'wildwood' was indeed closed or open, we can turn to the fossil record of plants and animals living at the time of the 'wildwood' to establish which of these two theories are broadly correct. Fossil beetles are very useful indicators of past environments and especially woodland environments. Previous work by the applicants has already established that beetles have considerable potential to establish whether Vera's ideas are borne out by the evidence, but we need to refine our understanding of what the fossil insect record means and how we interpret it. Essentially, we need to have a better idea of what 'open' or 'closed' woodland may look like in the fossil beetle record. In this project, we will collect recent fossil insect data from a range of ancient woodlands with different canopy structures (open, intermediate and closed) and well-recorded management systems, including grazing and mowing. The recent fossil data will be collected from sediment samples taken from the loose sediments at the base of small ponds in the middle of these ancient woodlands. A proportion of whatever insects are living in the woodlands will end up being deposited here. These recent fossils will probably represent individuals living in the vicinity over the last couple of decades. We will know from managment records that the areas sorrounding the ponds have not substantially changed over this period. By studying the recent fossil beetles and relating these statistically to the surrounding wooded areas, their canopy structure and management, we will be able to identify a fossil 'fingerprint' of what each site looks like in the fossil record. This will allow us to determine the broad characteristics of these types of woodlands which may be found in the fossil record. We have to study recent fossils rather than modern collected beetles as we are concerned with the interpretation of the fossil record, rather than the interpretation of the modern insect fauna. Of course, our study sites will not provide us with a complete range of potential types of woodlands which may have existed in the past, but they should allow us to separate 'open' from 'closed' canopy woodland and, possibly, establish the importance of management influences on their insect faunas. Finally, we will then collate and re-analyse published European fossil beetle data dating to c. 9,000-5,000 years ago and some selected earlier sites, in the light of refined understanding of beetle characteristics from forest environments. This will allow us to produce a more robust environmental reconstruction of native 'wildwood' and test whether the natural 'wildwood' was indeed closed or open canopy, providing contradictory or supporting evidence towards the landscape structure identified by Vera and its continued viability.
Organisations
Publications
Bunting M
(2008)
Adding time to the conservation toolkit: palaeoecology and long term wetland function dynamics
in Biodiversity and Conservation
Smith D
(2014)
Can dung beetles from the palaeoecological and archaeological record indicate herd concentration and the identity of herbivores?
in Quaternary International
Whitehouse N
(2008)
Fossil insects and ecosystem dynamics in wetlands: implications for biodiversity and conservation
in Biodiversity and Conservation
Whitehouse N
(2010)
How fragmented was the British Holocene wildwood? Perspectives on the "Vera" grazing debate from the fossil beetle record
in Quaternary Science Reviews
Whitehouse N
(2006)
The Holocene British and Irish ancient forest fossil beetle fauna: implications for forest history, biodiversity and faunal colonisation
in Quaternary Science Reviews
Whitehouse, N.J.; Smith, D.N. And Bunting, J.M.
(2007)
Eurasian Perspectives on Environmental Archaeology
| Description | This project was concerned with establishing vegetation structure using beetle fossils to examine the 'Vera grazing hypothesis' and early Holocene forest structure. The 'Vera hypothesis' has been concerned with the role of grazing animals in maintaining open areas in the primeval forest and has considerable implications in terms of how we manage woodland landscapes and ecosystems. Meaningful landscape interpretation of fossil insect data has, until now, been hampered by a lack of modern empirical studies to compare with the fossil record. Using modern 'fossil' beetles from 84 recent surface sediment samples, from 4 study sites (Dunham Massey, Epping Forest, Hatfield Forest and Windsor Great Park), we identified in excess of 3,500 minimum of individuals (MNI), representing more than 630 beetle species. Multiple surface sediment samples were taken from each pond, in tandem with vegetation surveys and GIS. We also removed samples for pollen analysis. We successfully established modern beetle/vegetation relationships for closed, intermediate and grazed/pasture ancient woodland at our study sites, providing us with the ability to determine canopy structure, open/pasture and grazing using the fossil record. This was established by analysing the key beetle functional groups recovered in the fossil record (wood/tree categories, pasture/open, dung, as a % of terrestrial MNI). There is a sharp difference between the proportions of beetles from 'parkland', 'intermediate', and 'full canopy' dense woodland. High tree/wood values (> 25%) characterise closed canopy sites, accompanied by very low pasture/open indicators (5-7%). Extensive parkland and wood-pasture landscapes are characterised by lower tree/wood values of c. 9-18%, with values of >30-50% of open indicators common. Relatively dense, 'intermediate' intensely grazed pasture woodland is characterised by higher tree/wood values (18-25%), relatively high pasture/open indicators (13-30%) and dung values of between 10-30%. Values of 1% dung beetles suggest areas from which grazing is excluded, whilst "naturalistic" grazing is indicated by c. 6-11% dung beetles. Thus, we demonstrated that it was possible to distinguish between the various characteristics of the study sites and that there is a statistically significant correlation between beetle faunas and canopy structure at each pond site, allowing us to be confident that we can distinguish between closed and open canopy woodland in the fossil record, although intermediate woodland types are less easy to distinguish. Further modern studies will be required to refine our models. When we compared the modern vegetation data, grouped into concentric 10m wide rings centred on the mid-point of each pond, with the % tree/wood beetle data, we established that the relationship between beetle taxa and abundance of woodland canopy is not linear, rather that it is a distance-weighted function and differs from the movement and catchment of pollen into the same ponds. This finding is important, as this provides us with an objective, statistically robust assessment of how well the fossil beetle record reflects past landscapes compared with pollen records and their inter-relationships. We re-analysed 28 early and mid-Holocene fossil beetle records (9500-2000 cal BC) using our refined analogue. Between 9500-6000 cal BC, the fossil record supports quite extensive open areas and a relatively dense "pasture woodland" during this period. Between 6000-4000, high tree/wood and very low pasture/open values are consistent with dense canopy woodland. Between 4000-2000 cal BC, there are major increases in pasture/open indicators, suggesting that grazing animals are not am important component of the landscape until the beginnings of agriculture and therefore not key players in structuring the "wildwood". This finding suggests that the "Vera hypothesis" is not supported by the fossil beetle data, but reveals a significantly more heterogeneous landscape during the earlier Holocene than previously argued, maintained by a range of processes (e.g. forest fires, wild blow, flooding). This is a significant finding. |
| Exploitation Route | This research can be exploited within the field of nature conservation in forested areas, pasture woodland and parkland areas to manage saproxylic invertebrates and mimc natural processes. Firstly, the research provides valuable insights into the structure of native forest. This research indicates that the British wildwood was characterised by significant spatial heterogeneity and that many of our ancient forest beetle inhabitants exploited this diverse range of habitats and ecological processes. In order for our modern forests to be well-managed for their invertebrates, similar ecological processes need to be allowed to be introduced. Secondly, the work provides an insight into species decline and causes of decline and ways in which loss of biodiversity may be halted and even reversed; thirdly, it provides insights into how the forest can best be managed to ensure survival of saproxylics and encourage their return. In terms of forest structure, forest managers need to be clear about what they are trying to achieve. The debate concerning the level of open-ness of forests and the role of grazing animals is particularly pertinent and it may no longer be appropriate to manage forested areas with the aim of developing closed canopy forest. Indeed, many forest invertebrates require a mixed mosaic landscape rather than full canopy forest. These habitats, often in glades and on forest edges, provide significant nectar sources near breeding habitat. Other taxa require sunny, open habitats with large amounts of dead wood, the type of habitat offered by pasture woodland suggested by Vera (2000) for past forests. Ancient wood pastures and parklands provide some of the most valuable habitats for many saproxylics rather than closed forest. The mixture of different species found in the fossil record during the early Holocene, periods when forests were largely free of human disturbance, suggests that substantial open areas did indeed exist although their extent may have varied across different forest types and areas. From a management perspective, it is therefore crucial that forest managers are aware of the history of a forest area and its current status. They should manage the area in the most appropriate way for the species which are present, whilst being aware of opportunities for species colonisation from nearby sites and potential to create new habitats. Any management activities and their impacts on invertebrates should be monitored to ensure that biodiversity is not adversely impacted by management activities. Where it is established that the species mix is such that pasture woodland would be beneficial, managers may allow the development of open glades as well as areas with a more closed canopy. In this scenario, allowing some level of grazing by wild or domesticated animals as a management tool is likely to be beneficial, although stock levels may need to be controlled in terms of their density, by season and their effects monitored to ensure that over-grazing does not occur. A consideration of baseline flora and fauna prior to the introduction of grazing will be essential, followed up by survey at intervals after the introduction of grazing. The use of animals as a management tool has often been perceived in negative terms by forest managers, but the development of the grazing debate and ongoing experimental work indicates the potential of this sort of approach, particularly in the management of large reserves, allowing managers to help maintain structural and species diversity within forest and encourage regeneration of light-demanding taxa . Current large scale ecological projects where this approach has proven beneficial include the Oostvaardersplassen reserve in the Netherlands and the New Forest, Hampshire, UK. It is likely that a range of other disturbance factors, in addition to animal grazing, can play important parts in creating open areas and maintaining ecological processes. Forests in the past appear to have been subject to a range of natural disturbances such as forest fires and storm damage, often creating open, sun-exposed places with considerable amounts of dying and dead wood. Forest fires, in particular, appear to have played an important role in maintaining an open character in at least some early Holocene forests, especially where dominated by flammable pine and birch. As a result of such fires, local vegetation patches and islands may have emerged locally quite frequently, creating semi-permanent open spaces and opening up the canopy of the forest. Again, whilst many foresters are understandably cautious about forest fires, from an ecological perspective they can be extremely useful and add to ecosystem diversity. Emulation and controlled use of these natural dynamics may be one key area in which managers may increase ecosystem structure, range and biodiversity. |
| Sectors | Communities and Social Services/Policy,Environment |
| Description | Can we determine open-ness in the palaeoecological record? Interpreting Holocene landscapes using modern analogue |
| Amount | £70,000 (GBP) |
| Organisation | Government of Northern Ireland |
| Department | Department for Employment and Learning Northern Ireland (DELNI) |
| Sector | Public |
| Country | United Kingdom |
| Start | 09/2011 |
| End | 08/2014 |
| Description | PhD awards: Refining the climatic, landscape, and ecological context of early human occupation in the early Middle Pleistocene |
| Amount | £70,000 (GBP) |
| Organisation | University of Plymouth |
| Sector | Academic/University |
| Country | United Kingdom |
| Start | 10/2013 |
| End | 09/2016 |