Editor’s Note: This article is based on a talk given by the author on Earth Day, 2012, at the Liberty Hyde Bailey Museum in South Haven, Michigan.
When we speak of saving the earth we usually mean saving life on the earth. The earth as a geological reality has already been ravaged for the resources we think we need. But our concern now is for the many species in the community of life on earth that are threatened. Many are facing extinction. Scientists who study life, past and present, such as paleontologists, ecologists, or evolutionary biologists, are telling us that we are already in the midst of the sixth great extinction. This loss of biodiversity increased as humans gradually became the dominant form of life. Unlike previous massive extinctions, such as the fifth extinction some 65 million years ago when a huge asteroid struck the earth and ended the age of dinosaurs, humans are now causing the current loss of bio- diversity — the sixth extinction.
CURRENT THREATS TO BIODIVERSITY
Humans are threatening biodiversity in a variety of ways. The paleoanthropologist, Richard Leakey, has summarized three ways in which humans cause the extinction of other forms of life: first by killing them for food, second, by introducing alien species into new ecosystems, and, third, by destroying the habitat of other creatures, as in deforestation. In other words, humans have taken over the land. But we can change how we live on the land by replacing alien species with native plants and reforesting our lawns. I will try to explain why this is important and necessary.
In this country, according to Douglas Tallamy, we have turned 54 percent of the land into cities, roads and suburbs. Only 41 percent of the land is now occupied by various forms of agriculture. Suburbanites control a significant percentage of the land in America and they can and should learn to share it with other forms of life. Our industrial way of life will also be threatening biodiversity in the near future as we literally change the climate. The gases given off by burning fossil fuels are causing global warming, and as the climate changes and weather becomes more unpredictable, it will add to the loss of species in a massive way.
There is much we can do to strengthen biodiversity as we prepare for climate change, and this is the main topic of this paper. But first I have to raise some questions about that most cherished icon of the suburb in America: the lawn. We have planted over 40 million acres of lawn in this country, and we spread more fertilizer on our lawns annually than India uses on all its cropland.
40 percent of all pesticides in this country are used on lawns. Americans spend 45 billion dollars a year on their lawns; they are a big business with a lot of vested interests. Lawns are watered liberally so they stay green and grow fast. And then they are mowed regularly with inefficient engines that produce as much pollution in an hour as driving a car 650 miles. All for vanity, since the lawn is an ecological desert.
Lawn grass, such as Kentucky blue grass (not native to Kentucky), is nearly always an alien species that provides food for no insects. Even worse, lawns may support the larvae of an alien pest, the Japanese beetle, according to Tom Small, who recently published a book on the value of native plants. Lawns are a nearly total ecological liability. Lawns should be replaced with native trees and bushes and wildflowers, which are not only beautiful but are able to provide food for a wide variety of insects. And these, in turn, provide feed for birds.
These food chains are essential for a viable ecosystem. But as people yielded to the appeal of exotic varieties peddled in garden catalogs, they often planted varieties that were not digestible by the insects that evolved here. According to the entomologist, Douglas Tallamy, our native flowering dog- wood supports 117 species of moths and butterflies, while the Kousa dogwood from China supports no insect herbivores at all. Our native oak trees support the growth of over 500 species of insects, more than any other tree. The Monarch butterfly loves the nectar of the so-called butterfly bush, Buddleia davidii, a non-native plant, but they need native milkweed in order to reproduce. In other words, specific insect larva evolved with certain specific plants and only their leaves are chemically digestible by the insects that evolved with them. Alien plants or trees that did not evolve with our native insects are often touted as being resistant to insect damage. But when we choose such alien plants that are resistant to insect damage, like the Norway maple, many insects are deprived of sustenance.
LOSS OF ECOLOGICAL INTEGRITY
I realize that we live in a society that does not love insects. Insecticide manufacturers thrive by fostering “insectophobia.” When we see an insect we scream, “Eek, a bug!” and reach for the spray can. But the way to deal with “bad” insects is to strengthen biological pest control with insect predators and parasites. This can reduce populations of insects that cause us trouble. Spraying broad spectrum pesticides that kill insects indiscriminately is counter-productive. Insects serve a vital ecological function: they eat plants and store the energy from plants and make it available as they are eaten by birds and other animals. And insects are nutritious, with more protein than beef. Finally, the biodiversity of a vital ecosystem is what sustains our lives as well. Humans also depend on the web of life. As insect populations decline, so do the birds they would otherwise feed on.
The World Conservation Union has estimated that 12 percent of all bird species are extinct because of habitat loss and invasive species. Since 1960 we in this country have lost visible. The introduction of an alien plant or insect, into an area where it has no natural enemies, means that it can easily become a troublesome invasive. Local examples include especially plants like the autumn olive or the multiflora rose, which gradually crowd out native plants.
In other regions of the country plants like the kudzo vine or mile-a-minute have become serious pests. I am trying to eradicate autumn olive on my land because it is so invasive and it does not provide food for insects. Let’s turn now to some of the many advantages of adding more native plants to our suburban lots. Because native shrubs and perennial wild flowers are deeply rooted, they are more drought resistant, save water, and sequester more carbon. These are important characteristics as we face global warming. As we plant such perennials on our lawns we also reduce carbon emissions by having less lawn to mow. Even more important is the fact that native perennials add to biodiversity by providing food for a wide diversity of insects. Finally, a greater diversity of insects can provide more biological pest control with predators and parasites and thereby reduce the need for insecticides. As an organic farmer and gardener I have always trusted in a natural balance in raising crops, and it works. It will work even better if we have more plants to feed insects.
BIOPHILIA CAN HELP TO SUSTAIN BIODIVERSITY
Edward O. Wilson, the famous biological writer, feels confident that we all share what he calls biophilia, a love of nature, and that we humans want to protect, restore, and enjoy biodiversity. Many of us prefer to live in natural or rural areas. Liberty Hyde Bailey did promote the subdivision of land for rural residents at a time when the automobile made life in the suburbs possible. I believe we want to co-exist with birds and small animals. We enjoy watching butterflies, and many are beautiful even in the caterpillar stage of their development. If we damaged the bio- diversity of our region by planting alien species, we did so mostly out of ignorance. Or at least I did so when I planted exotic flowers without thinking about whether they would be good for insects.
Now that we know the importance of native species, our love of nature can be reinforced by a sense of moral obligation. We should do the right thing in the light of the knowledge we now have. And the right thing, in summary, is to plant native perennial flowers, shrubs and trees on parts of our lawn. Because of bio- philia, many people have already done so. This is the kind of ecological restoration that can be done only in our suburban yards, and it will contribute to more biodiversity even as it makes our places more beautiful. Saving the Earth,
How can we begin this ecological restoration? First, we must get informed. A good source of information is the book that Tom Small, a retired English professor, published last year: Using Native Plants to Restore Community. It is a beautiful book full of practical advice. Tom, and his wife Nancy, recently deceased, organized the Kalamazoo Area Chapter of The Wild Ones which is dedicated to the promotion of native plants. Several states have chapters of The Wild Ones. Another book I found very helpful was written by Douglas Tallamy, a professor of entomology, and his studies of insect and plant interactions demonstrate the importance of providing more native plants that insects can digest.
His book is entitled Bringing Nature Home: How you can Sustain Wildlife with Native Plants. As the importance of native plants catches on they are becoming widely available through commercial sources. It is, however, important to be sure they are native in your local area. Many County Conservation Districts make native wildflowers, bushes and trees available at their spring sales. It is also important to recognize that we can not count on government programs to restore native plants because most of the land available for native plants is owned and controlled by rural or suburban residents. As we face a changing climate, which adds new threats to biodiversity, we can help to preserve species with more native plants.