Biodiversity and Land Use: How Ancient Practices Shaped Britain
Exploring how the interplay between the natural environment, climate and human land use has shaped the landscapes of the British Isles.
Understanding how climate and human action have affected vegetation cover and natural habitats is key to defining the complex relationships between land use and biodiversity. In this article we present our project on land use change and shifting patterns in biodiversity.
At a time when human actions, climate change and habitat transformation are a growing concern, defining how ancient land use affected the natural world may provide important lessons as we face an unprecedented climate crisis.
The scope of the project
The three-year project began in the spring of 2019 and aims to define and understand patterns of biodiversity and land-use throughout the British Isles during the Holocene, which is the present geological epoch beginning after the end of the last Ice Age, about 11,500 years ago.
It is a collaboration between Historic England, the University of Plymouth and the University of Birmingham, and is funded by the Leverhulme Trust as the Biodiversity and land use project.
We are pooling and harmonising previously compiled datasets for three environmental indicators: pollen, plant macro-remains and insects. Records are mostly obtained from online databases and other published sources. The project is also reaching out to archaeological companies for data not captured in existing databases, as development-funded archaeology is generating an ever-increasing wealth of information. We aim to involve data contributors in the research and welcome new contributions. We have held two archaeobotanical workshops so far where participants have brought their own data and learnt about the database which we are using to record and standardise the information. We plan to hold a virtual workshop online this summer.
Charred and waterlogged plant remains
Anne de Vareilles and Ruth Pelling (Historic England) are collating archaeological records of charred and waterlogged seeds, fruits and nuts. These remains are retrieved during excavations and give us an insight into arable practices, the biodiversity of arable fields, and settlement environments. Waterlogged plant remains found in anaerobic sediments (devoid of oxygen) are informative of the vegetation and biodiversity within a past settlement.
Charred plant remains are usually created when by-products from cereal processing and food preparation activities, such as crop weeds and cereal chaff, are burnt and discarded. These remains can tell us about the types of crops grown and how they were cultivated, thereby providing information on land use. The ecology of arable weeds can reveal details about the types of soils cultivated and the labour dedicated to the preparation and maintenance of fields.
As an example, small, intensively cultivated plots intrinsically interconnected within a mixed husbandry regime (as has been suggested for the Neolithic period) will not have had the same imprint upon the natural landscape and biodiversity as the large, extensively managed open-field systems (known as champion field-systems) of the medieval period.
Waterlogged plant remains found in anaerobic sediments (devoid of oxygen) are informative of the vegetation and biodiversity within a past settlement. Records of waterlogged and charred remains are uploaded into ArboDat, an Access database administered in the UK and Ireland by Historic England and designed to standardise, store and share archaeobotanical data. Using this programme enables us to search for patterns in land use across time and space, from the smallest site, to regional trends and wider developments within the British Isles over many millennia
David Smith (University of Birmingham) uses fossil insect remains from his own research, published sources and the BugsCEP database (built to store records of insects in the past) to describe changes in site habitats, vegetation and land use.
Similarly to waterlogged plant remains, insect remains are only preserved in anaerobic conditions, and are therefore not as abundant as charred plant remains. However, they are of great interpretative value, providing refined climatic and ecological details. Some insects are very particular to their environment, living in highly specific conditions. As such, they can reveal the temperature, humidity and organic matrix (fur, grain, straw, wood, dung, and so on) of the habitat they once lived in. These details are useful in defining site environments and detecting small-scale variations in biodiversity. Such trends can also be observed for wider landscapes around settlements where another spectrum of insects reflects patterns of land use.
Jessie Woodbridge and Ralph Fyfe (University of Plymouth) are amalgamating, digitizing and harmonising published fossil pollen datasets and diagrams from across the British Isles. Their two main sources of pollen data are Michael Grant’s British Pollen Database BPOL, and the European Pollen Database.
Pollen datasets are being transformed into records of vegetation diversity change using the REVEALS approach, an analytical method that incorporates information about pollen productivity and dispersal (Trondman et al. 2015). Diversity and ‘evenness’ indices reflect species richness and indicate how equally distributed species were within a landscape. Spatial patterns in diversity can reveal information about ecological ‘memory’ and can show how landscapes have been transformed through time. Comparisons with macro-botanical and insect datasets allow us to investigate the impacts of human land use on past and present vegetation cover and diversity. Together, pollen, plant-macrofossils and insect remains can disentangle effects of natural phenomena, like climate, from those induced by human activities.
Fluctuations in past human populations
Periods of human population increase have been associated with major land cover transformations in the past.
Fluctuations in past human populations in the British Isles have been estimated by Andy Bevan and others (University College London) from the densities of securely-dated archaeological sites. These data are being used within this project to explore the relationships between population change, land use, land cover and biodiversity.
The project is still in the data gathering phase, although some initial results can be shared. Trends in land cover and vegetation diversity over the Holocene have been mapped using 272 fossil pollen datasets.
Variations between woodland cover and more open landscapes are seen in diversity and evenness indexes. For example, dense woodland cover is seen to reduce by about 30 per cent with the arrival of a new farming population at around 4000BC, leading to increased floral and faunal diversity.
However, there are archaeological periods when population ‘booms’ do not correlate with trends in vegetation diversity, suggesting that it is not simply the number of people using the land, but rather how the land is used that affects land cover and biodiversity. The distribution of sites with charred plant macro-remains is, in itself, an indication of the extent of farming across the British Isles in any given period.
The range of crops and associated weeds show variations in uniformity during the last 6000 years, with periods of greater conformity (eg. Roman) and those of greater diversity (eg. early medieval) in the range of crops and their methods of cultivation. Such practices will have affected biodiversity in the agricultural landscape, which can be described in finer detail from insect remains. Insects are a great proxy for land use and vegetation, capable of showing, for example, the development of field systems seen through the increase in open-ground and dung associated species.
Excavations over many decades have produced an immense amount of evidence for ever changing and evolving landscapes. Archaeological sciences can extract information from plant and insect remains to demonstrate changing conditions on individual sites. This information can be pooled from various locations to illustrate patterns of change at a broader scale and provide a bigger picture of how British landscaped developed through time.
Collating pollen, plant macro-remains and insect datasets allows a more nuanced picture to be defined of the history of human land use, its relationship with land cover and biodiversity and the ‘ecological legacies’ imprinted upon modern landscapes.
About the authors
Dr. Anne de Vareilles
Anne is a Post-Doctoral Research Fellow on the project, employed by Historic England. Anne is an experienced archaeobotanist with a research background on European plant macrofossils, and the development of agriculture in prehistory.
Dr. Jessie Woodbridge
Jessie is a Post-Doctoral Research Fellow on the project at the University of Plymouth. Jessie's research background is focussed on reconstruction of Holocene palaeoenvironmental change using palaeoecological techniques based on peat and lake-sediment archives.
Buckland, P.I. & Buckland, P.C. (2006). BugsCEP Coleopteran Ecology Package. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series # 2006-116. NOAA/NCDC Paleoclimatology Program, Boulder CO, USA.
Buckland, P.I. (2007). The Development and Implementation of Software for Palaeoenvironmental and Palaeoclimatological Research: The Bugs Coleopteran Ecology Package (BugsCEP). PhD thesis, Environmental Archaeology Lab., Department of Archaeology & Sámi Studies. University of Umeå, Sweden. Archaeology and Environment 23, 236 pp + CD.
Trondman, A.-K., Gaillard, M.-J., Mazier, F., Sugita, S., Fyfe, R., et al. 2015. 'Pollen-based quantitative reconstructions of Holocene regional vegetation cover (plant-functional types and land-cover types) in Europe suitable for climate modelling'. Global Change Biology 21: 676-697, doi: 10.1111/gcb.12737
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You can download this article in PDF format as part of Historic England Research magazine Issue 16.