Our research group is involved in a number of projects seeking to understand the drivers of paleoenvironmental change during the Quaternary period. Some major themes are described below.
Wetland dynamics in the Holocene and Pleistocene: hydro-climatic change and carbon storage
Wetlands provide numerous ecosystem services. One critical area is carbon storage, yet information is lacking on how carbon storage in peatlands responds to hydro-climatic change. Through analysis of peat cores, our group is developing new reconstructions of Holocene paleoclimatic and paleohydrological changes, and associated impacts on wetland vegetation, peat and carbon accumulation. These results can be integrated into process based models used to predict impacts of climatic changes and other disturbances on these important areas. A major area of focus is the Hudson/James Bay Lowlands, one of Canada’s most extensive and most important wetlands. This region also contains some of the largest and best preserved deposits in Canada which date to Pleistocene Interglacials, and these are also an area of focus. In addition to northern peatlands, we are also working on projects to unravel the history of wetlands in the Great Lakes region, and to quantify the effects of wetland losses due to human impact. Techniques used in these projects include radioisotope dating, pollen analysis (aka palynology), diatom analysis, plant macrofossils, testate amoebae and chemical analysis of peat samples. Research questions include the effects of climatic and water-level changes on wetland plant communities through the Holocene, successional processes in the context of highly dynamic systems, and the identification of invasive species and other biogeographic trends in emergent macrophytes through pollen and herbarium-based research.
Paleoclimatology and paleolimnology in Arctic Canada
Arctic ecosystems are changing rapidly due to global warming, but the impacts of these changes are poorly understood due to lack of information about long-term climate history and ecological responses to climatic changes. Paleoenvironmental records document the effects of past climatic changes on ecosystem dynamics. We are using Holocene-age paleolimnological records from the sediments of Arctic lakes to (1) reconstruct spatio-temporal patterns of Holocene paleoclimates in the Canadian Arctic, (2) quantify the long-term impacts of climatic changes on terrestrial and aquatic ecosystems, and (3) determine relationships between species composition, biological productivity, biodiversity, and responses to paleo- and recent climatic changes. Some of our sites were selected for specific examination of recent human impact; for example we are collaborating on a paleolimnological study to track the multiple effects of urbanization on fish populations in a lake in Yellowknife, NWT.
Other projects have looked at paleolimnological records across geological gradients on Prince of Wales Island, reconstructing climate history for the past two millennia on the Melville Peninsula as part of a collaborative International Polar Year project focussed on both archaeology and paleoenvironments, (“Dynamic Inuit Social Strategies in Changing Environments”), and using paleolimnology, algae and benthic invertebrates to monitor freshwater ecosystem health in Sirmilik National Park on northern Baffin and Bylot Islands.
Our Arctic projects involve the recovery and analysis of sediment cores collected from small lakes and dated using the radioisotopes 210-Pb and 14-C. Diatoms (microscopic algae with siliceous cell walls) are a major emphasis in our work on arctic lakes, owing to their abundance, good preservation and value as specific ecological indicators. Sedimentological analyses include magnetic susceptibility, loss-on-ignition, particle size analysis, and measurements of biogenic silica and humic acid concentrations. The research has strong field and laboratory components, but also emphasizes quantitative approaches to integrating data from many indicators and from many regions using statistics and GIS. Also, the research is tightly linked to modern ecological studies of the indicator organisms.
Holocene landscape development at the boreal – mixed forest ecotone
We are using a series of lake sediment records to analyse the controls on long-term landscape change at sites transitional between the boreal and temperate forest biomes. Forest ecosystems are influenced by climate, but also by disturbance and long-term processes such as succession, soil development and chemical weathering. Many of these sites have also been affected by significant human impact since the onset of the industrial era. Through the analysis of multiple proxy indicators in lake records, the relative importance of these factors can be shown. Major research sites include lakes near Sudbury, Ontario and in the Turkey Lakes Watershed in the Algoma District of central Ontario.
Paleoenvironments in southern Africa
Southern Africa is a critical region for studying the relationship between environmental change and human evolution. The region has experienced phases of significant environmental change resulting from variations in large-scale atmospheric and oceanic circulation patterns. We are working on projects seeking to quantify these changes, and in collaboration with archaeologists, determine how these paleoenvironmental changes may have affected human evolution and adaptation. Paleoenevironmnetal analyses are being conducted at an Early Stone Age site for correlation with archaeological records and regional syntheses with existing data.