Dr. Thomas Larsen

I am interested in understanding how changes in resource availability and biogeochemical cycling disrupt ecosystems and the communities inhabiting them. My goal is to create benchmarks of resource availability by comparing past and current disturbance regimes and to reference conditions prior to and during the Anthropocene. These benchmarks are important for forecasting how ecosystems will equilibrate to anthropogenic changes, devising strategies for sustainable use of natural resources, and mitigating adverse effects of global change. The pervasiveness, magnitude, and variety of human impacts leave little doubt we have entered a distinct era from an environmental viewpoint. While geologists may be concerned about the detectability of the Anthropocene in future geological records, this consideration is in my opinion not relevant for (paleo)ecological research as humans have modified ecosystems ever since we accelerated megafauna extinctions during the Pleistocene. Hence, a key component of my research is characterizing nonstationary environments and relating these changes to how humans currently use and have used resources in the past.

To create benchmarks of past and current ecosystems, my research has a strong methodological component. Notably, I am one of the lead developers of a method termed stable isotope fingerprinting of amino acids that can overcome many of the challenges of reconstructing diets and nutrition with prevailing tracer methods. These carbon stable isotope patterns can trace the biosynthetic origins of proteinogenic amino acids to algae, bacteria, fungi, and plants. The method is also showing great promise of categorizing taxa within these phylogenic groups and resolving the dietary niches of consumers. They are particularly well suited for deep investigation of diets and primary producers across time and space because the fingerprints remain largely invariant across different environmental conditions. Recent research also shows that the amino acid isotope patterns can inform about the relative composition of dietary macronutrients. I also use nitrogen stable isotope ratios of amino acids to infer the trophic positions of consumers. As the research leader of the Biochemistry Group here at SHH, I take a keen interest in other biomolecular techniques to understand natural ecosystems and past lifeways such as reconstructing animal domestication, human demographics, dairying, and documenting how plants were used in the past for their scents and psychoactive properties. To that end, we identify and characterize dietary lipids, fecal steroids, and a suite of secondary metabolites from ancient sediments and artifacts.