Peter R. Leavitt
Professor, Canada Research Chair in Environmental Change and Society
Director, Canadian Institute of Ecology and Evolution and Institute of Environmental Change and Society
Office: LB 265.1
E-mail: Peter.Leavitt at uregina.ca
Research in my laboratory combines ecosystem and in situ experiments, modeling, paleolimnology, and long-term (20 yr) ecological research (LTER) to quantify the factors that regulate the structure and function of lakes and improve strategies for their protection. Our main themes and advances are summarized below.
Paleoecology- We pioneered the use of mass budgets and whole-ecosystem experiments to calibrate the use of algae, pigments, invertebrates and stable isotopes as fossils in lakes. In particular, we are global leaders in the use of pigments from algae and bacteria as indicators of environmental change, including novel compounds that allow reconstruction of past UV radiation (UVR) environments. Our methodology is now used by >10 international institutes and research groups, as well as Canada Research Chair and NSERC Industrial Chair programs. Recently, we developed new methods to reconstruct past nutrient influx, ecosystem variability, water temperatures, and food-web contamination by metals, and have applied our analytical approaches to help protect lakes on 6 continents.
Nitrogen Effects on Lakes- Our research demonstrates that the structure and function of lake ecosystems is regulated on annual to millennial time scales by the influx of nitrogen (N) from external sources, including atmospheric deposition, biological fixation of N2, migratory fishes, terrestrial dissolved organic matter (DOM), forestry, agriculture, and urban pollution. Significantly, industrial N has polluted even remote polar lakes for over 120 years, thereby defining the onset of the Anthropocene. We show for the first time that early lake productivity and ontogeny is regulated by influx of N, not phosphorus (P), in sharp contrast to many modern freshwaters. As well, we uniquely find that N and other subsidies from marine salmon regulates algal beta-diversity, predation regimes, productivity, and basic N biogeochemistry of natal lake ecosystems. Finally, our experimental, LTER and fossil research has resulted in a new paradigm for lake eutrophication by demonstrating for the first time that pollution of P-rich lakes with urea and other forms of N increases production and toxicity of cyanobacteria by up to 500% on diverse temporal and spatial scales. This work resulted in legislation to regulate lake pollution with N, including the 2011 Save Lake Winnipeg Act.
Climate and Lakes- This theme investigates how lakes regulate climatic processes and how, in turn, climate influences lakes and society. Our prairie LTER program reveals that climate warming since 1990 has increased lake pH by 1.5 units and stimulated CO2 capture by lakes to rates equivalent to 50% of provincial agricultural emissions. Further, we show that influx of energy (E) increases spatial synchrony of lake properties, whereas the influx of mass (m) reduces temporal coherence, particularly that of aquatic food webs. Our whole-lake experiments, surveys, and stable isotope analyses reveal that variation in jet stream position, and consequently winter precipitation, is the main climatic mechanism structuring central Canadian lakes, despite chemical and food-web effects of E exchange during summer. Finally, we are developing a series of paleo-climate reconstructions to forecast the risks of droughts on the Canadian Prairies. These conditional probability analyses estimate that the risk of severe (1930s) droughts is as high as 45% by 2030 AD, with expected losses of $650 billion. This information is being used by crop insurance, agricultural and hydroelectric corporations in all Prairie Provinces to evaluate their susceptibility to climate extremes.
Ecosystem Sustainability and Management- Application of basic ecological knowledge is essential to sustain ecosystems and their services. Here we use our novel limnological and statistical approaches to quantify causes of environmental degradation in diverse aquatic ecosystems, including First Nation’s territories, coastal estuaries, prairie lakes, northern freshwater deltas, salmon nurseries, high latitude ecosystems, alpine lakes, and iconic sites worldwide (e.g., Winnipeg, Windermere, Neagh, Champlain, Great Salt, Vattern, Kinneret, Okeechobee). In all cases, we balance novel scientific discovery with clear management recommendations to initiate legislative change and enable sustainable management (see above). Our leadership has resulted in the Energy-mass (Em) flux framework, a new conceptual paradigm adopted by 15 international research groups to quantify the unique and interactive effects of humans and climate on lakes, and formally unify limnology and paleoecology.