Pests and diseases threatening urban trees under a changing climate

The predicted change in our climate is likely to inflict particular stresses on the trees and other plants constituting urban and peri-urban greening schemes, and this may increase their susceptibility to certain pests and diseases. This review highlights the various ways in which climate change may affect the health of urban trees in Britain. In summary, climate change may alter patterns of disturbance from pathogens and herbivorous insects through physiological changes in the host plant. The expected changes in temperature and moisture availability will also directly affect the development and survival of the pests and pathogens, and their natural enemies, competitors and vectors. This may alter the impact of native pests and diseases and increase the populations of some species not currently recognized as pests to epidemic proportions. Perhaps most significantly, climate change is very likely to enhance the suitability of our climate for a range of non-native pests and pathogens, many of which are brought in unknowingly on infected planting stock sourced for new greening schemes. The global trade in 'plants for planting' is a recognized pathway for the accidental introduction of pests and pathogens even though plant health legislation exists to minimize such accidental introductions. The limitations of the procedures currently in place are discussed.