We Need to Prevent Forest Loss by Invasive Pests

Forests are being damaged and lost worldwide by damage from invasive pests that could be prevented. Usually there is a time lag between arrival of an exotic pest and its recognition as a devastating outbreak. Such outbreaks can only be prevented by preventing the introductions of the pests.


Emerald ash borer and white pine blister rust are examples of the many insects, nematodes and pathogens that have been introduced from other countries and, after variable time lags, are now devastating North American forests. A non-native pathogen (Cronartium ribicola) has driven white-bark pine in Alberta down to the endangered list. This fungus was originally imported on white pine from Europe about 1910 and has spread into all the five-needled pines in North America.


Such pests can eliminate a host tree and thus eliminate all the other organisms dependent on that host. Elimination of a tree species from a forest also can change the structure of the ecosystem in that forest. Gaps are filled by other tree species and both the ecosystem and the spatial structure are changed and unlikely to return to the original.


Non-native pests invade mainly as a result of international trade without proper regulation of imported materials. Frequency of damaging outbreaks of imported forest pests is more closely related to Gross Domestic Product than it is to percentage forest cover in the nation.


Emerald ash borer arrived in shipping pallets. Pests are commonly introduced in living plant material imported by the nursery and plantation trades. Pests can be spread by movement of the same materials across the receiving continent.


Lists of prohibited pests do not prevent their entry because so many pests are unknown to science and can’t be identified until it is too late. Reduction in import of “luxury” plant materials and products and quarantine for up to two years of such products when they are imported is the only workable preventative.


For more information see: Roy et al., Frontiers in Ecology and the Environment 2014; 12(8): 457-465.


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