Modelling crop productivity and variability for policy and impacts of climate change in eastern Canada

A simple scalar crop growth index, GrowEst, was used to calculate plausible weekly crop growth indices for 101 sites over 40 years in eastern Canada. The experimental design allowed the calculation of regional growth and regional variability over time. The research is reported in three sections: development of GrowEst for eastern Canada, policy applications, and scenarios of the impacts of climate change. From the growth index we propose a single statistic, the median integrated seasonal growth index, MIGI to describe the overall fitness-for-growth of a particular site across years, or of a particular year across a geographical area such as eastern Canada. The growth index generally increased from 1960 to 2000 due mostly to increasing temperatures. When mapped, the highest potential growth was adjacent to the Great Lakes and along the St Lawrence River Valley. Variability through time was lowest at locations where the indices were highest. Comparison of these data with historical regional yields indicated that potential yields may not have been captured by current technologies. Two potential policy applications of GrowEst modelling were demonstrated: the determination of crop insurance payments taking account of potential yields and spatial variability; and in urban land-use planning. Future scenarios were calculated from five climate change models for time periods up to 2099. All scenarios caused increases in growth indices. Most predicted that the length of the growing season would increase by 5–7 weeks but that incidences of moisture deficit would also increase. We conclude that climate change is most likely to cause increases in potential productivity which may be largely negated by increasing moisture deficits. Opportunities are identified for innovation to capture current and future potential yield and to reduce yield variability.