[PCA] Exotic Invasives

Hopkins, Jerry Jerry.Hopkins at dnr.state.oh.us
Wed Dec 27 07:29:24 CST 2006


Perhaps a current example of an artificially introduced species would be helpful. The Emerald Ash Borer (Agrilus planipennis Fairmaire) is a native of Asia where it attacks stressed trees of several genera and species. It was likely transported to North America in packing material. In it's new home (here), it attacks healthy ash trees. That is, all healthy ash trees. This small insect is not trying to invade it is simply exploiting an opportunity in an ecosystem that did not share its co-evolution and contains no developed checks and balances. However, the effect is that this small insect is going to effectively remove an entire genus (Fraxinus) of trees from the North American hardwood forests. That is about 8% of a typical forest population depending on the locality. For reference the chestnut blight removed one species, Castanea dentata.

The problem is not that species migrate it is that species are sometimes artificially transported to a new habitat skipping the co-evolutionary process that limits its movement by natural selection. This is not a condemnation of the ornamental horticulture industry. It is simply a suggestion that we think carefully when forming opinions on this issue. I used the example of an exotic insect since the cause and effect occur relatively quickly are easier to observe. The same principle applies to plant species but it takes longer to see the effect. Think: kudzu.   

Jerry C. Hopkins
Nursery Operations Supervisor
Marietta State Nursery
740-373-6574 at Marietta
jerry.hopkins at dnr.state.oh.us
 

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