Climate-related Transboundary Pests and Diseases

Global trade, both in variety and quantities of goods moved, is increasing year by year. For example,WTO statistics indicate that between 2000 and 2005, global sea and air freight rose by around 20percent with volumes now exceeding 7 billion tons per year. Trends in eco-climatic variables underdifferent climate change scenarios also show marked differences in key drivers such as temperature,rainfall, soil moisture, etc. This juxtaposition of dramatically increased trade-driven international pestmovement and more gradual shifts in climatic suitability in previously unsuitable regions of the worldis providing new opportunities for plant pests to enter and establish in new locations. Within the dramatically increased trade statistics, it is possible to determine which commodities are thehigh risk pathways for international movement of pests of phytosanitary concern. While wood, woodproducts and wood packaging have been recognised as key pathways and are subject to stringentphytosanitary controls, it is now becoming increasingly apparent that it is the ‘plants for planting’pathway that poses the greatest current and future risk. Trade in live plants, often complete with rootballs and associated soil, is increasing rapidly and globally. Full circumnavigation of the globe is nownormality for live plants and, while there are phytosanitary rules in place, they tend only to reflectknown pests. Those pests not on the lists of recognised organisms will consequently tend to be missed. Transport along a pathway does not, of course, always result in successful establishment of pests innew locations. Previously, many organisms could not establish because of climatic unsuitability,reflecting the ecological and climatic barriers that determine distributions of pests in their naturalranges. The fact that distributions of pests in their native ranges is now changing and has been linked toclimate change, indicates that climatic suitability for pests moving along trade pathways is alsochanging. Particular examples include the pine processionary moth, Thaumetopoea pityocampa, whichhas moved northwards in Europe over the past 50+ years and mountain pine beetle, Dendroctonusponderosae, which is causing devastation well north of its previous range in NW Canada. Both haveclimatic components in explaining their range shifts. Prediction of which pest will become damaging innew locations is not easy but lessons can be learnt from the ways in which pest organisms are adaptingto climate shifts in their current locations. Overwinter temperatures, synchronicity of insect emergencewith bud burst of hosts in the spring, reduced tree defences arising from climatic stress and warmersummers accelerating development are all aspects that provide insights into future pest adaptations to climate change. There is no doubt that the complex interactions between climate, pest and host tree willrequire detailed study to increase our understanding and allow development of pest managementstrategies for the future. However, it does seem inevitable that the increased opportunities for pests toencounter new and suitable eco-climatic zones for establishment will result in many new infestationsand challenges in pest management.