Several months ago the redoubtable Nancy Smith of the Western New York Land Conservancy loaned me her copy of Douglas Tallamy's Bringing Nature Home. Nancy was so enthusiastic about this book that I reluctantly promised to read it.
The book sat on my shelf until a week ago when I decided that I owed Nancy at least a scan of its contents. Within ten minutes I realized that this is one of the most important nature books published in my lifetime. I urge everyone interested in our role on this planet to read this book and I only hope its message will be conveyed to homeowners.
Tallamy's message may seem simplistic. He urges us homeowners to purchase native plants for our gardens and to replace the alien plants already there with natives.
I think that all of us support that general idea. We would like to promote native plants as a kind of ecological patriotism. But Tallamy, an entomologist, places the idea in its larger context. His message subtext: each native plant supports a wildlife community; an alien plant supports no such community.
What does this mean? Consider two examples. First, that beach grass (phragmites) that is taking over our marshlands from our native cattails. In its native Australia phragmites supports 170 species of herbivores, here it supports five.
That's the alien downside. A single species, our native black cherry supports 400 herbivore species.
Your first reaction may be: wait a minute, most of those herbivores are bugs and who wants more bugs? The answer is: we should all want them. Many of those insects turn out to be the larvae of beautiful moths or butterflies. Those and others also serve as food for birds.
If you want birds in your garden during their breeding season, you need to have insects for them to feed on. They are necessary to support the birds' increased energy needs for reproduction and the growth of their young. After a winter of feeding many bird species, when spring arrives, you may feel that the birds have abandoned you. This is very likely because either you lack native plants with their associated insects or you use insecticides to suppress them.
Because they provide so little sustenance to the biotic community, alien plants lead to sterile gardens and Tallamy tells us that a sterile garden "is teetering on the brink of destruction. It can no longer function as a dynamic community of interacting organisms. Its checks and balances are gone. Instead, the sterile garden's continued existence depends entirely on the frantic efforts of the gardener alone."
Of course, what applies to our gardens applies to our parks and woodlands as well. Tallamy again: "A healthy woodland is a collection of plants and animals that are more or less in balance. Yes, there are insect herbivores eating the plants that grow there, but keeping those herbivores in check are dozens of species of insect predators, parasites and diseases. These, in turn, are eaten daily by the birds, amphibians, and small mammals that reside, or simply hunt in the woodlot. With rare exceptions, no one member of the food chain dominates another; if one species in an essentially sound system does start to run rampant, it is soon brought into equilibrium by the other members of the community. That is why all of the leaves in native forests aren't eaten by insects, why we don't see huge defoliation events (except when an alien species like the gypsy moth is on the loose) and why a forest in balance brings us a sense of aesthetic pleasure. If you carefully inspect individual leaves in a forest, you will find that a small portion of most of them have, in fact, been eaten by insects; but the overall effect is still one of beauty, not destruction."
We need to change our thinking of gardens and parks from collections of individual plants to wildlife communities.
I urge you to begin replacing the
your gardens with natives. You can get help in identifying native plants from
these local nurseries: