Doug Tallamy was surprised at how perfect the leaves looked on surrounding shrubs and herbaceous plants. As an entomologist he would have expected to see holes, chewed edges and other evidence of herbivorous insects feeding. It occurred to Tallamy that, as summer waned, unblemished leaves were a sign that insects, such as larval butterflies and moths, were having trouble.
He quickly solved the mystery. The untouched foliage belonged almost exclusively to exotic Eurasian plants. Indigenous insects utilize plants with which they evolved. They don’t readily adapt to newcomers. Landscapers and Botanical Gardens have long promoted insect and pest resistant plants. But native butterflies and moths are too important to be called pests. Their absence represents the loss of several links in the food chain. Simply stated, a lack of diverse native plants, equals a lack of diverse native insects, equals a lack of diverse native birds. Instead of being pleased with perfect pristine plants, Tallamy became concerned about loss of native diversity, enough to look into this further.
The landscape industry has historically focused on exotic plants. The foliage tends to be pest and disease resistant; garden designs and horticultural training often harkens back to European estates with their unique aesthetic qualities, and, as a consequence, inadvertently ignore Native American vegetative options. Habitat considerations have not been a major focus. But for the sake of non chemical pest control, and protecting our native critters, we need to get back to planting natives.
Plants form the foundation of ecosystems. Through the magic of photosynthesis they capture solar energy, producing leaves, stems, roots, seeds, fruits, etc. which support a wide array of us animals. Herbivorous insects represent the crucial connection making the energy in plants available to specific animals, such as birds. Of the critters that occupy planet Earth, some 37 percent are herbivorous insects.
The importance of this cannot be over stated. Ninety six percent of birds feed insects to their developing young. And they need a lot of food for a clutch of famished nestlings. A pair of chickadees, for example, may gather well over 500 caterpillars each day to feed a half dozen hungry mouths. That’s nearly 9,000 butterfly and moth larvae in a span of a couple weeks. And their foraging forays take place within only about a 50 meter radius of the nest. Their success is in all our hands.
Dr. Tallamy, in his 2007 book, “Bringing Nature Home,” does an excellent job of summarizing our growing ecological dilemma as well as offering ways to meet our many environmental challenges.
He points out, for example, that species diversity is directly proportional to area. Islands have precious little diversity, whereas continents support vast numbers of species. Removal of forests and prairies has caused fragmentation and has reduced quality habitats to what are essentially “islands.” Since there is a direct correlation between number of species and area, if fifty percent of America’s pristine land is converted for agriculture, cities, highways, etc., over time there will be a loss of fifty percent of species. Trouble is, today ninety five percent of America’s wild lands have been ‘tamed,’ and put to various uses. Worst case scenario: we could witness the gradual loss of 95 percent of the flora and fauna that greeted the Pilgrims when they landed at Plymouth Rock.
There are well over 300 million people consuming the U.S. landscape and there is no national recognition of the limits of land to sustain this impact or to support even more millions. We simply haven’t left enough intact habitats for most species to avoid extinction. Already there are huge declines in native bird populations. Just within the past 40 years, according to the Audubon Society, Bobwhite quail have declined by 82 percent, eastern meadowlark population has dropped by 72 percent, and evening grosbeaks are down by 78 percent… These ‘canaries in the coal mine’ are sending a clear message. We have a problem.
Nature Preserves, National Parks, National Wilderness Areas, National Wildlife Refuges, state and municipal parks, while important, are not adequate to preserve America’s biodiversity. According Tallamy’s research, if we don’t modify the places in which we live, work, and play to meet not only our own needs, but the needs of other species, nearly all species of wildlife native to America could disappear.
We continue to unwittingly introduce destabilizing microorganisms, insects, mites, weeds, etc. Examples are legion. The chestnut blight which wiped out American chestnut, one of our most important and stately forest giants, was brought here with exotic trees. Gypsy moths were introduced in order to make silk and can defoliate vast areas. The emerald ash borer was introduced in wooden crates and is killing off ash trees. West Nile fever was brought over in a load of tires. The American beech faces a “new old” threat, beech bark disease, which is now spreading westward. The hemlock woolly adelgid is a newly introduced insect that has been killing hemlocks in Pennsylvania and is spreading westward. The list goes on and on.
Gardeners are to blame for many of our wildlife woes, having inadvertently introduced a plethora of exotic invasive species and new plant diseases. But they will also play a huge roll in restoring and protecting our native wildlife.
It’s OK to plant a few horticultural varieties of plants, as long as they aren’t overly aggressive, but for the sake of our birds, it’s crucial to provide abundant varieties of native plants in home landscapes, churches, parking areas, city parks, along roadways, etc. Dr. Tallamy includes in his book a list of preferred regional plants to sustain native insects.
Have your home landscape becomes a model of how we fit in to nature. We’ve seen amazing results when there are adequate numbers of native critters around the home. Spiders control insects, birds control spiders, wasps and spiders control various insects, including flies, lady bugs control aphids, hornets keep garden pests at bay. Diversity is the key.
For more information and/or lists of some of the best native plants see: