Potential impact of climate change on European agriculture: a case study of potato and Colorado potato beetle

Abstract: European agriculture is facing the challenge of managing the impact of climate change on food security. Agriculture in a northern temperate climate is likely to benefit from higher temperature and longer growing season while, in the south, crop productivity is likely to decline. Such changes in climate could also affect the population dynamics of insect pests. The Colorado potato beetle (CPB) is one the most destructive and widespread pests affecting potato plants, and can substantially reduce the potato harvest if left uncontrolled. Potato (Solanum tuberosum) is one of the main food crops in Europe. It is therefore important to investigate the potential for climate change adaptation in Europe by assessing the effects of a temperature increase on CPB and potato crop phenology. The main objective of this thesis is to examine how the inter-annual variability of weather impacts on crop and pest phenology, and their interrelationship under global warming in Europe. We developed phenological models, one for the Colorado potato beetle and one for the potato. The models were developed to assess potential effects of a warmer climate on timing of i) CPB emergence after winter hibernation, ii) voltinism, iii) diapause, iv) food availability (e.g. potato model based on different temperature response functions) and finally v) crop-pest synchrony over Europe. We calculated the timing of completed development of the first and second CPB generation, and assessed the geographical and inter-annual variation in the number of generations per year. The results show that two generations per year may occur more frequently at the current distribution border at 55°N, increasing the risk of northward migration to the Scandinavian countries. In this region, the current climate is not warm enough to sustain the completed development of one generation in all years, and the region does not host a permanent population. For the potato, the model was parameterised on the basis of three planting dates, which were used to assess the management impact on the timing of emergence and maturation of both early and late potato. The estimates of phenological development were assessed by comparing two developmental thresholds (0°C and +2°C) and three temperature response functions. The results show that a linear temperature response function is essentially sufficient for current climate conditions in northern Europe, so optimum and upper thresholds should be considered in climate change impact assessments to predict realistic growth. The model was run with temperature data bias corrected according to quantile mapping method, and indicated a slightly higher risk of temperature stress than the corresponding runs with temperature data corrected by linear scaling. In conclusion that ensembles approach, using data from more than one climate model, can reduce the epistemic uncertainty. This study also highlights the importance of knowledge about species-specific temperature response and reliability of climate model data in order to reduce the uncertainties.