Remote sensing of recent changes in northern peatlands

Background

Peatlands are organic-rich wetlands, where waterlogged conditions allow carbon-rich detritus to accumulate. Despite covering less than 3 % of the Earth’s land surface (Xu & Morris et al., 2018), peatlands are thought to store between a sixth and a third of all global soil carbon (Gorham, 1991; Page et al., 2011). By far the largest concentrations of these important landscapes are in the mid- and high-latitudes of the northern hemisphere, particularly northern Canada, Scandinavia and Western Siberia (Tarnocai et al., 2009). These areas have experienced rapid climate change in recent decades, and are projected to continue to warm more rapidly than almost anywhere else on the planet over the coming century (Collins et al., 2013; Cohen et al., 2014). Concern exists that the northern peatland carbon store may be vulnerable to rapid changes in climate, and that thousands of years’ worth of accumulated carbon may be returned to the atmosphere as these systems begin to warm and dry (Ise et al., 2008; Ciais et al., 2013).

Despite this importance of northern peatlands to global biosphere-climate feedbacks, large knowledge gaps exist about how these ecosystems are currently changing in response to recent climate change. This project will assess changes in the hydrology, vegetation and geomorphology of northern peatlands during recent decades, on spatial scales ranging from the continental to individual field sites. There is potential for measuring changes in peatland surface wetness, for instance the widespread development of thermokarst lakes, using a range of classification approaches (e.g. normalised difference wetness index (NDWI), segmentation-based classification); while changes in vegetation, increasingly apparent in a “greening Arctic”, may be assessed using the normalised difference vegetation index (NDVI). There is the opportunity to quantify surface lowering using either repeat optical DEMs, altimetry or interferometry, and at smaller spatial scales, geomorphological changes such as expansion and contraction of peatland pools could be assessed by analysing repeat aerial photography, including drone surveys, and possibly also historical air imagery that is available in Alaska, northern Scotland and other peat-rich regions. This more detailed analysis is likely to employ cutting-edge techniques such as Structure-from-Motion and laser scanning that have been extensively employed elsewhere by the supervisory team (e.g., Smith et al., 2016) as well as more traditional field-based techniques. Gridded instrumental climate data will be used to explain any temporal trends yielded by these analyses along with other geomorphological and topographical controls.

There will be exciting opportunities for the student to visit remote field sites, including in the Arctic, to ground-truth interpretations of satellite data and to collect aerial drone photographic surveys. The student will also be encouraged to build collaborations with the broad group of international experts working in this topical area.

Objectives

This project will use a powerful combination of remote sensing techniques at a range of scales, and instrumental climate data, to study recent changes in northern peatlands at a range of scales. More specifically, the project will address the following objectives:

  1. To detect and quantify recent changes in the vegetation and surface wetness of northern peatlands across large areas of the northern hemisphere, using satellite imagery.
  2. To detect and quantify changes in vegetation, surface wetness and geomorphology in northern peatlands, at smaller spatial scales (e.g., regional scales to specific peatland sites) during recent decades, using a time series of drone photography mosaics and Structure-from-motion.
  3. To establish the role of recent climate change in driving these recent changes in northern peatlands.

Fit to NERC Science

This project is closely aligned with two NERC research areas: 1) Terrestrial & Freshwater Ecosystems, particularly Earth surface processes and ecosystem-scale processes; and 2) Climate & Climate Change, including using instrumental climate data to understand recent environmental change in northern peatlands.

Potential for High Impact Outcome

The project will contribute to one of the most pressing environmental issues of our time – the vulnerability of one of the world’s most carbon-dense ecosystem types to recent and ongoing climate change. The research has been designed so that each of the objectives (above) will lead directly to an important, high-profile journal article that the student will lead. The student will be guided in this endeavour and all other aspects of the project by the supervisors, who have a track record of publishing in some of the world’s most prestigious scientific journals, and who have pioneered relevant methods in the geosciences (e.g., Smith et al., 2016).

Training and Supervision

The student will work under the supervision of Dr. Paul Morris, Dr. Duncan Quincey and Dr. Mark Smith in the School of Geography, where they will become a member of the River Basins Processes and Management research cluster. The project will provide the student with high-level training in (i) peatland science; (ii) state-of-the-art remote sensing techniques (e.g. Structure-from-Motion); (iii) interpretation of instrumental climate data; and (iv) advanced data analysis skills. The student will be supported throughout by a comprehensive PGR skills training programme that follows the VITAE Research Development Framework and focuses on knowledge and intellectual abilities; personal effectiveness; research governance and organisation; and engagement, influence and impact. Training needs will be assessed at the beginning of the project and at key stages throughout. The student will be encouraged to participate in the numerous training and development courses that are run within the university to support PGR students, including statistics training (e.g. R, SPSS), academic writing, grant writing, and other relevant skills (see http://www.emeskillstraining.leeds.ac.uk/). Supervision will involve regular meetings between all supervisors, while an independent Research Support Group will provide the student with external guidance at regular intervals throughout their studies.

Student profile

The student should have a keen interest in contemporary environmental change, demonstrable research skills in remote sensing and GIS techniques, and a strong background in a physical geography, Earth sciences, plant sciences, environmental sciences or a related discipline.  Some experience of research into peatlands and/or wetlands is also desirable but not essential.

References

Ciais P.C. et al. (2013) Carbon and Other Biogeochemical Cycles. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Chapter 6. Eds.: Stocker T.F., et al. Cambridge University Press.

Cohen J., et al. (2014) Recent Arctic amplification and extreme mid-latitude weather. Nature Geoscience, 7: 627–637.

Collins J., et al. (2013) Long-term climate change: projections, commitments and irreversibility. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Chapter 12. Eds.: Stocker T.F., et al. Cambridge University Press.

Gorham E. (1991) Northern peatlands: Role in the carbon cycle and probable responses to climatic warming. Ecological Applications, 1: 182–195.

Ise T., Dunn A.L., Wofy S.C. & Moorcroft PR (2008) High sensitivity of peat decomposition to climate change through water-table feedback. Nature Geoscience, 1: 763–766.

Page S.E., Rieley J.O. & Banks C.J. (2011) Global and regional importance of the tropical peatland carbon pool. Global Change Biology 17: 798–818

Smith M.W., Carrivick J.L. & Quincey D.J. (2016) Structure from motion photogrammetry in physical geography. Progress in Physical Geography, 40: 247–275.

Tarnocai C., et al. (2009) Soil organic carbon pools in the northern circumpolar permafrost region. Global Biogeochemical Cycles, 23: GB2023.

Xu J., Morris P.J., Liu J. & Holden J. (2018) PEATMAP: Refining estimates of global peatland distribution based on a meta-analysis. Catena, 160: 134–140.