Reconstructing long-term relationships between reindeers and environmental change in the Arctic

Overview

Herd herbivores are essential components of Arctic ecosystems. They play important roles in sustaining local food webs, maintaining terrestrial ecosystems and acting as food sources for Indigenous peoples. Wild reindeer/caribou (Rangifer tarandus) are especially integral to Indigenous culture and identity. However, the viability of herding in the Arctic under current and projected climate change is cause for concern (Nakashima et al., 2012). Historical Rangifer population records collected since the 1960’s have provided valuable insights into the species vulnerability (Vors and Boyce, 2009). The Dolphin and Union herds in the Cambridge Bay area of the Canadian high Arctic have experienced sharp declines (>50% over the last twenty years). In parts of Fennoscandia (e.g. Finnish Kevo sub-Arctic), herds have experienced a staggered, rather than sharp, rate of decline. Increased Rangifer mortality rates are linked to (1) increased thaw-refreezing events that form impenetrable ground surface ice layers, preventing access to vegetation food sources; (2) reduced sea ice, which disrupts migration routes with consequences for food availability, infection rates and likelihood of drowning; and (3) competition with other land users and alterations in food web dynamics. Regional differences in rates of Rangifer decline may relate to differences in environmental conditions. For example, sea ice plays an important role in Rangifer migrations in Cambridge Bay, whilst the importance of changes in precipitation, temperature and freezing events in Fennoscandia has been highlighted. Rangifer population pressures will continue to increase under projected climate warming.

This PhD project aims to assess the regional sustainability of current herds and herding practices under environmental changes by developing long-term records of Rangifer population and climate. These millennial-scale records will be developed from naturally accumulating lake sedimentary archives that can be independently dated. The project will use a combination of geochemical and palaeoecological analyses of lake sedimentary archives from the Canadian high Arctic and Finland to provide multi-proxy evidence for changes in temperature, precipitation, Rangifer herd dynamics, nutrient cycling, and vegetation change. The specific objectives of the PhD are to:
• Characterise the timings and intensities of reindeer herding in Finland and the Canadian high Arctic and how they have changed over the Holocene
• Reconstruct Holocene hydroclimate and vegetation dynamics
• Characterise the impacts of reindeer herding on lake nutrient cycling and vegetation change
• Determine the contribution of environment change in shaping Arctic reindeer herding dynamics.

Methodology

The project focuses on using organic geochemical and palynological analyses of lake sediments. During fieldwork in Finland and Canada, the student will undertake bathymetric surveys of lake study sites, analyse water column physiochemistry, recover Holocene sediment cores from the lake centre. These sediments will undergo lithostratigraphic analysis using loss-on-ignition (LOI), mineral magnetics and XRF scanning. To assess changes in the timings and intensities of reindeer herding activities the student will date the lake sediments using radiocarbon and use lipid biomarkers (sterols, bile acids) (Prost et al., 2017) to track faecal input into the lake. The student will also use pollen and leaf wax n-alkanes to reconstruct vegetation changes and hydrogen isotopes and bacteriohopanepolyols (BHPs) to reconstruct past hydroclimate (Holtvoeth et al., 2019; O’Connor, 2020). Depending on how the project develops there will be opportunities to explore other lipid biomarker analyses to complement the proposed palaeoenvironmental analyses. For example, the analyses of GDGTs could be included to reconstruct changes in temperature.

The project benefits from working closely with project partner Dr Kimberley Davies (Bournemouth University, UK), who will create landscape and vegetation models using pollen data.

Project Timeline

Year 1

Review existing literature on Arctic reindeer herding and long-term environmental change. Plan and conduct fieldwork in Finland and Canada to extract lake sediment cores. Start laboratory analysis on sediment cores, which will include sediment descriptions, physical properties analysis (elemental chemistry (XRF) and LOI) and sub-sampling the core for lipid biomarker and pollen analyses. Conduct initial rangefinder radiocarbon dating of the cores. Complete first year progression paper to detail the project overview, research questions and methodology.

Year 2

Continue laboratory analysis (lipid biomarkers, pollen analysis). Complete radiocarbon analysis and produce core chronologies. Present initial results at a national conference (e.g., QRA). Submission of review chapter for publication. Write up of methods chapter.

Year 3

Finalise laboratory work with an extended visit for training in BHP lipid biomarker analyses at the Royal Netherlands Institute for Sea Research. Data analysis and interpretation. Present results as an international conference (e.g., EGU/AGU). Write up of results chapters and begin overall thesis writeup.

Year 3.5

Preparation and completion of final chapters of the thesis and submission of papers for publication.

Training
& Skills

This project will develop cross-disciplinary transferable skills in problem solving, project management, experimental design, data analysis and visualisation and report writing.

High-levels skills will be developed in:
• Field techniques with training in lake surveying and coring.
• Laboratory analyses with training provided on sediment core logging, radiocarbon dating, XRF scanning and lipid biomarker extraction, processing and analysis at Durham University state-of-the-art research laboratories. Pollen extraction and identification training will take place at Newcastle University and training on BHPs will take place at the Royal Netherlands Institute for Sea Research.
• Computational/statistical analyses with training on computer programming in R for data visualisation and statistical analyses provided at Durham and Newcastle Universities.

The candidate will also benefit from broad skills training provided in-house at Durham (e.g. science communication, thesis writing, writing for grants and publications, presentation skills) via the Geography Department and the award winning Career and Research Development (CAROD) group. Furthermore, a broad range of environmental science training is provided within the IAPETUS Doctoral Training Partnership. Training requirements of the individual will be identified and met through the development of a personal training plan.

The presence of national and international collaborators ensures that the student has excellent opportunities to develop a strong multidisciplinary research network. Research skills and awareness of on-going research will be developed through regular participation in Durham’s Physical Geography weekly seminar series and other research group meetings, and participation in external national and international conferences to support development as an independent researcher.

References & further reading

Holtvoeth, J., Whiteside, J., Engels, S., Freitas, F., Grice, K., Greenwood, P., Johnson, S., Kendall, I., Lengger, S., Lücke, A., Mayr, C., Naafs, B., Rohrssen, M. and Sepúlveda, J. 2019. The paleolimnologist’s guide to compound-specific stable isotope analysis – An introduction to principles and applications of CSIA for Quaternary lake sediments. Quaternary Science Reviews.

Nakashima, D.J., et al., 2012. In “Working Group II of the Intergovernmental Panel on Climate Change”, United Nations Educational, Scientific, and Cultural Organization (UNESCO), Paris, France, and United Nations University (UNU), Darwin, Australia, 82 pp.

O’Connor, K. 2020. Biomarker and stable isotopes of plants, soils and water from a Northern Alaska Transect for paleoclimate calibrations. Doctoral Dissertation, University of Notre Dame.

Prost, K., Birk, J. J., Lehndorff, E., Gerlach, R., and Amelung, W. 2017. Steroid Biomarkers Revisited – Improved Source Identification of Faecal Remains in Archaeological Soil Material. PLOS ONE 12, e0164882-e0164882.

Vors, L.S. and Boyce, M.S., 2009. Global Change Biology 15, 2626-2633.

Further Information

Please contact Dr Helen Mackay (helen.mackay@durham.ac.uk) when applying to this project. Note that there is scope to tailor specific components of this project towards the individual interests of the student.

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