Why do populations fluctuate across a spatiotemporal landscape? This question is the common thread that links my various research interests. Understanding spatiotemporal population dynamics is critical to species conservation and management, yet the dynamics are not well understood, largely because population dynamics are inherently complex and often not amenable to experimentation. Models allow us to infer process from pattern when the experimental means are impractical or impossible. My research approach is to work at the interface of empirical data (observational and experimental) and theoretical modeling. I build data-driven models with the aim of understanding both the patterns and the underlying mechanisms driving complex spatiotemporal population dynamics across large spatial scales and use the models to test hypotheses about causal mechanism(s).
While professor Johnson has interest in the population dynamics of a wide range of organisms, his research has focused on insects. Forest insects are the focus of the majority of my research. Forest insects are great model systems because they are abundant and easily manipulated, much is known about their biology, and their dynamics are rich in interesting patterns such as fluctuations of five orders of magnitude (i.e. outbreaks), periodic cycles, spatial synchrony, and traveling waves (temporal lags in spatial synchrony where population peaks shift across a spatial gradient).