Importance of Native Plants in the Ecosystem Garden
It has been my feeling for many years that native plants were the key to developing habitats for wildlife in our gardens, but there was no “proof.” Although much has been written on this subject, none of it was based on a scientific exploration of the subject, mainly because there was none. But now all of that is changing, thanks in large part to Doug Tallamy and his students at the University of Delaware. The publication of Bringing Nature Home: how native plants sustain wildlife in our gardens was just the beginning.
This book makes the best argument I have ever read about the absolute importance of the use of native plants in our gardens, and should be required reading for every landowner.
Tallamy clearly lays out the connection between native plants and insect biomass. No native plants means no insects, which means no birds, bats, frogs, toads, or other amphibians. Plants are the only organism able to take the energy of the sun and transform it into a form that can be used by other organisms. The largest group of these organisms is the insects which provide a crucial link in turning energy into protein, so critical for the continuing success of all other species.
Insects provide the necessary link in the passage of energy from the sun, through plants to insects, which are a huge part of the food web for other wildlife. Most song bird species, whatever the adults may eat, require insects to successfully rear their young. The protein that is obtained from insects is not available in any other form. Without the plants, the insects cannot survive. Without the insects, the birds are lost.
Exotic Plants Do Not Support Much Wildlife
Mr. Tallamy presents a very compelling argument as to why exotic plants are less desirable, why invasive plants represent such a danger to our ecosystems and may carry diseases that our native plants have no immunity to, and why native plants are so necessary to the survival of all other species.
“Proof” of the necessity of native plants in the conservation garden continues to be collected at the University of Delaware. One of Tallamy’s students, Karin Burghardt, studied the difference in avian (bird) numbers and larval lepidopteran (butterfly caterpillar) biomass between suburban sites landscaped primarily with native plants versus more traditionally landscaped sites with exotic plants.
She found that the higher the percentage of native grasses, forbs, and shrubs there was at a site was directly correlated to higher numbers of native nesting birds, butterflies, and moths. Correspondingly, those sites with a higher percentage of exotic plants had far fewer native nesting birds and lepidoptera. This is very reminiscent of the research on the coffee farms in Mexico, Central, and South America, where it was found that higher proportions of the native forest correlated very strongly with higher numbers of birds, insects, and other wildlife.
What do we take away from this? We need to break away from the “sameness” model and incorporate more locally native plants into our landscapes. If you are trying to attract birds and butterflies, you need to have native plants!
Native plants Support Huge Numbers of Butterflies and Moths
Another of Tallamy’s students, Kimberley Shropshire, took on the enormous task of plodding through thousands of academic research studies and compiling, for the first time, a list of plants with the numbers of lepidoptera (butterflies and moths) using each as a host plant.
She correlated the plants in each study with each species of lepidoptera that relied on that plant. Reading this spreadsheet is a fascinating experience, and a dream come true for me: to have a list of plants and know for a fact just how much each plant really does benefit wildlife. So now we can resoundingly answer the question I am asked more than any other: Which plants should I choose? And the answer is now so easy: choose locally native plants based on how many species each can support!
Tallamy’s book should be required reading for every homeowner and gardener (and all other land owners/managers, too). Have you read it? What do you think?
 Burghardt, K. T., Tallamy, D. W., & Shriver, W. G. (2009). Impact of native plants on bird and butterfly biodiversity in suburban landscapes. Conservation Biology, 23(2), 219-224.
 Tallamy, D. W., & Shropshire, K. J. (2009, in press). Ranking Lepidopteran Use of Native Versus Introduced Plants. Conservation Biology.
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