New York City

Dave Johnston has spent two decades as a research scientist who reconstructs ancient ecosystems and their environmental contexts. He studies the evolution of microorganisms and their relationships to the oceans and atmosphere. With techniques such as isotope geochemistry, theoretical models, and experiments with modern microbes, his team examines how the biosphere and chemical cycles have changed throughout our planet’s history. Johnston received a BS in Environmental Studies and Philosophy from Bates College in 2002 and Ph.D. in Geology from the University of Maryland, College Park in 2007 where he worked on developing novel stable isotope systems with James Farquhar. Dave moved to Harvard as a Microbial Sciences Institute Fellow from 2007-2009 blending field geology and redox geochemistry (with Andy Knoll in EPS and OEB) with microbial physiology and experimental microbiology (with Pete Girguis in OEB). 

Dave joined the EPS Faculty in 2009, was promoted to Full Professor in 2016, and was named Dean of Science in May 2026. Johnston served nearly 15 years as co-director of Graduate Studies in Earth and Planetary Sciences, has sat on numerous department committee, and also served on the Dean of Science’s Faculty Advisory Committee and Executive Committee. He is currently the president of the Geobiology Society, a scientific organization that unites researchers from various disciplines.