Abstract:
Globally, over the last 30 years, there has been an increase in the number of reports of tree mortality related to anthropogenically driven climate change. Changes in climate not only directly affect plant and tree growth but also influence insects and microbes (pests and pathogens) that interact with plants. Increased temperatures have, for example, led to an explosion in mountain pine beetle (Dendroctonus ponderosae) populations resulting in the death of more than 10 million hectares of Pinus contorta in Canada and the United States of America. This review considers the known and predicted impact of anthropogenic climate change on insects and pathogens in forest environments where large scale tree die-offs have been experienced. Most of these reports are from the Northern Hemisphere, but there are also instances in the Southern Hemisphere, including South Africa where tree die-offs are occurring and where climate is believed to play a role. For example, Euphorbia ingens trees in South Africa have been reported to be dying-off in unprecedented numbers. In this case, it has been suggested that opportunistic pests and pathogens, driven by changes in climate, may be contributing to the death of these trees. Climate change associated tree die-offs are not only of concern in the natural forest environment but are also important in planted forests where commercial impacts are relevant. Overall, climate change has become an important issue relating to tree diseases and it must be taken into consideration when investigating the factors involved in unexpected tree die-offs.
