Transients, temperature and invasive species

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Management based only on the long term, or equilibrium, state of ecological systems can overlook important issues arising from temporary, or transient, behaviour. We may mistakenly conclude a conservation action is unsuccessful because the ecosystem takes years to respond, or we may believe that an invasive species will have no impact because the long term climate conditions are unfavourable. For example, emerald ash borer can cause large urban tree removal costs (estimated at $1 billion in Canada) even if this invasive insect does not permanently persist in northern cities, since trees die within 5 years of infestation. My overall research goal is to understand and predict the management implications of transient behaviour in ecological systems. One cause of transients is temperature fluctuation. Climate change is making temperatures more variable and autocorrelated, so that, for example, several years with warmer than average winters will occur together. Responses to these fluctuations could drive systems away from equilibrium states. Understanding how temperature fluctuations will affect whole ecosystems, however, first requires predicting impacts on individual species. The transient behaviour of single species is also important for management. In Canada, invasive species costs to fisheries, agriculture and forestry are ~$20 billion per year. The number of invasive species has been increasing since the 1950s as a result of global trade, but climate change is accelerating the impacts of highly temperature-dependent invasives such as insects. Of course, not all non-native species persist in new environments, and models of long term climate tolerances are often used to predict risks. This approach, however, does not address the probability that invasive species could increase in the short term. For the next 5 years, my team will investigate the effect of temperature fluctuations on the transient behaviour of invasive populations. Species like plants, insects and fish are strongly impacted by temperature, which can change age at maturity, the number of offspring, and probability of survival. We will incorporate temperatures of the environments where these species live (e.g., the underbark microclimate for woodboring insects) into population models to predict short term growth and persistence. We will test our predictions on model species in controlled conditions, and apply them to emerging invasives such as Asian longhorned beetles and black carp. This research will advance our understanding of transients, provide methods for predicting the impact of temperature fluctuations on ecological systems, and forecast risks from invasive species. Students on my research team will transfer the quantitative skills they acquire to agencies tasked with managing invasive species, such as the Department of Fisheries and Oceans and the Canadian Forestry Service, thus ensuring that our findings have an impact on science policy that benefits Canadians.