IAP2-22-447

Reconstructing Arctic climate change and its impacts on reindeer populations

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. Reindeer/caribou (Rangifer tarandus) are also integral to Indigenous culture and identity. However, the viability of future 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 provide 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 records will be developed from naturally accumulating lake sedimentary archives that will be independently dated. The project will use geochemical analyses of newly-collected lake sedimentary archives from the regions such as the Finnish and Canadian Arctic 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 from Arctic case study regions and how they have changed over the Holocene
• Reconstruct Holocene climate dynamics in study regions
• Characterise the impacts of reindeer herding on lake nutrient cycling and vegetation change
• Evaluate the role of environment change in shaping Arctic reindeer herding dynamics.

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Image Captions

Winter fieldwork view of Finish lakes in reindeer roundup area.,Lake coring from the ice in Finland. More fieldwork can be conducted as part of this project depending on the interests of the candidate.,Colourful lipid biomarker extracts can be seen here in the round bottom flasks. The project will analyse these extract to reconstruct changes in climate and reindeer populations.

Methodology

The project focuses on using organic geochemical analyses of lake sediments. During fieldwork in the Arctic, the student will survey lake study sites, analyse water column physiochemistry and 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) and nitrogen isotopes to track faecal input into the lake. The student will use carbon isotopes and leaf wax n-alkanes to reconstruct vegetation changes and hydrogen isotopes to reconstruct past hydroclimate (Holtvoeth et al., 2019). Depending on how the project develops there will be opportunities to explore other lipid biomarker analyses to complement the proposed palaeoenvironmental analyses. For example, analyses of GDGTs could be included to reconstruct changes in temperature. There is scope for the successful candidate to shape the direction of the laboratory analyses based on their interests (e.g. the project lends itself well to sedimentary ancient DNA/palaeoecological analyses). Full training will be provided in all analytical and fieldwork methods by the supervisory team.

The project benefits from working closely with project partners and organic geochemists Dr Darci Rush (Royal Netherlands Institute for Sea Research, NIOZ) and Dr Melissa Berke (University of Notre Dame). There are opportunities for the successful candidate to conduct a placement for training in Orbitrap GC-MS analyses in the Netherlands and/or compound-specific stable isotope analysis in the USA.

Project Timeline

Year 1

Review existing literature on Arctic reindeer herding and long-term environmental change. Plan and conduct fieldwork in the Arctic (e.g., 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 stable isotope analyses. Conduct initial 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 and stable isotopes). Complete radiocarbon analysis and produce core chronologies. Present initial results at a national conference (e.g., BOGS/QRA). Submission of review chapter for publication. Write up of methods chapter.

Year 3

Finalise laboratory work with an opportunity for further analytical training at the Royal Netherlands Institute for Sea Research and/or University of Notre Dame, USA. Data analysis and interpretation. Present results as an international conference (e.g., EGU/AGU/IMOG). 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 full training provided on sediment core logging, radiocarbon dating, XRF scanning, stable isotope analysis and lipid biomarker extraction, processing and analysis at Durham University state-of-the-art research laboratories. The analyses can be shaped to the interest of the successful candidate (e.g. to include sedimentary ancient DNA/palaeoecology) and there is scope to design an international placement at the Royal Netherlands Institute for Sea Research to be trained in state-of-the-art Orbitrap GC-MS analysis.
• 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 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 research group meetings and seminar series, DurhamARCTIC institute meetings and events, and 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. 207, 101-133.

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.

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 declines of caribou and reindeer. Global Change Biology. 15, 2626-2633.

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