by Doug Tallamy, Timber Press, 2007, 2009
The following is a review of this book, written by Bob Kortright for the October issue of the Toronto Field Naturalist newsletter, reprinted with their permission. Although this book is not recent, its message certainly is timely. Doug Tallamy can also be heard in person at the Toronto Botanical Garden, Tuesday, October 25, at 7:30 p.m. His topic is “Rebuilding Nature’s Relationships at Home”. TBG lectures
Tallamy’s book provided a long overdue treatment of a vital and underappreciated subject – the importance of replacing non-native plants with native ones. Given the evidence he marshals, it could have been titled How Traditional Horticulture is Wiping out our Wildlife, because traditional horticulture is largely based on non-native plants, which cover an ever-increasing fraction of the landscape around us. While the impact of invasive plants on native plants is acknowledged, at least by naturalists, I think most of us still don’t appreciate that non-native plants have contributed to the decline of our birds and other wildlife, whether they are invasive or not.
Non-native plants support fewer insects than native plants, because native insects did not evolve with them, so usually cannot eat them. Most of our birds depend almost entirely on insects to feed their young. There are some insects feeding on non-native plants (either generalist herbivores or non-native insects that were imported with the non-native plants.) And there are a few non-native plants that are similar enough to related natives that our insects do not appear to be able to tell the difference. But, why would we import Asian crabapples when our native crabapples are so similar that our insects cannot tell the difference? Especially when every plant we import carries the risk of bringing a plant disease or pest like the ones that have devastated our elms and the American Chestnut, and are devastating our butternuts, beech, and ash.
However, the fact that some insects eat some plants of alien origin does not change the argument –- non-native plants support fewer herbivores than native plants, and therefore fewer omnivores and carnivores in turn. So, we need native plants to sustain our wildlife.
While our society is unlikely to reject the use of non-native plants in agriculture, I see no excuse for using non-native plants in our gardens and parks, for which there are excellent native substitutes. Non-native tree, shrub and vine species which are invading natural areas (ailanthus, Siberian elm, Manitoba and Norway maples, black locust, European birch, Asian bittersweet and Asian honeysuckles, European buckthorn…) should be removed and replaced with native species as soon as possible, unless they are providing shade and where they are unlikely to spread to natural areas.
by Bob Kortright