Although it is well known that occasional insect plagues can severely affect forests, scientists have not studied the effect of normal background insect feeding to the same extent. New research modelled the impact of increases in insect damage on a species of birch tree (Betula pubescens) native to northern Europe. The model uses existing and predicted climate change data and suggests that insects could affect the mix of tree species in the future.
Eastern areas of northern Europe could see insect damage to leaves increase by up to five per cent and, in Scandinavia, an increase in temperature of one degree centigrade in summer could almost double insect damage to the leaves of this birch species.
Insects cause primary leaf damage but leaf destruction also has a secondary effect. The affected tree competes less effectively with other tree species. This means that the future composition of forests could be affected by increases in normal levels of insect damage. This suggests that increases in insect feeding should be considered when predicting how forests will alter as a result of climate change.
Rising temperatures will allow more insects to survive the winter, and also influences their growth and reproduction. There is already growing evidence that insects are spreading further North in Europe, so northern forests will increasingly be exposed to southern insect pests.
This northern march of insects has wide ranging implications for productivity, forest composition and distribution, forest management and biodiversity. The drastic leaf loss associated with an insect outbreak has already been shown to have an impact on ecosystems. This studies shows that background insect damage could have also a strong impact in the long-term. Both types of insect damage should be considered when assessing how an ecosystem is likely to respond to climate change, and these should be included in vegetation modelling.