Dec. 22, 2018
Bringing Nature Home: How You Can Sustain Wildlife With Native Plants
Go native! Dr. Douglas Tallamy’s message is simple: “By favoring native plants over aliens in the suburban landscape, gardeners can do much to sustain the biodiversity that has been/is our richest asset.” Creating functioning ecosystems in our growing suburbs is key to saving the planet. Dr. Tallamy visited the University of Mississippi in Oxford this spring for a full day of day of discussion, free public lecture, and an evening fundraiser for the Strawberry Plains Audubon Center.
Dr. Tallamy is professor and chair of the Department of Entomology and Wildlife Ecology at the University of Delaware. Insects are an important part of this book for a very valid reason: they are the basis of the food chain for a variety of species. John Losey and Mace Baughn have valued the ecosystems services provided by insects at $57 billion per year. If insects were to disappear, our own extinction would not be far behind.
Tallamy explains clearly and explicitly the impact that humans have on the natural world – just in the way we landscape and how monoculture lawns and exotic ornamentals put our survival at risk. The exciting good news is that we can all bring positive results to the planet and our own well being just by enhancing our understanding of the vital role of plants and modifying our gardening and landscaping habits.
Plants are Earth’s lifeblood; neither we nor anything else can live without them. Plants form the first trophic level: the energy that sustains all life. We invariably take the benefits plants provide for granted: the oxygen we breathe; the mass of roots in the forest that filter the rainwater, providing us with fresh water; and the primary role of plants in the food chain. Nearly every creature on the planet owes its existence to plants – the only organisms capable of capturing the sun’s energy through photosynthesis and turning that energy into food for the rest of us.
The diversity of animals in a particular habitat is very closely linked to the diversity of plants in that habitat. Did you know that plants’ leaf chemistry is their most important factor determining taste? Greater numbers of plant species mean more opportunities for animals to obtain their energy without interfering with one another. Plant diversity creates niches to which animals adapt over evolutionary time.
The second trophic level compromises all the animals that eat plants: the herbivores. “I cannot overemphasize how important insect herbivores are to the health of all terrestrial ecosystems,” he writes. A large percentage of the world’s fauna depends entirely on insects to access the energy stored in plants. Birdsare a particularly good example of such organisms; 96% of all terrestrial bird species in North America rely on insects and other arthropods (typically spiders that eat insects) to feed their young! Insects are unusually nutritious. Pound for pound they contain more protein than beef and their bodies are extremely high in valuable energy. So, if we want to have abundant members of higher trophic levels, like birds, in our managed ecosystems, we must have their primary food source: insects.
The depressing part is that humans have been destroying the ecosystems that support us: abetting extinction, replacing wildlife habitat, and surrounding ourselves with sterile environs. “If we need space we take it – all of it.” We feel completely justified in filling in a pond or cutting down a woodlot, in destroying the plants and animals that depend on those habitats. We term it “vacant land,” which is then bulldozed, leveled, and prepared for row after row of suburban housing with acres of manicured lawns that the owners spend hundreds of hours and hundreds of thousands of dollars mowing, all the while generating air pollution. Tallamy says that suburbia is the place where saving the planet begins.
“To understand why we need to restore the ecological integrity of suburbia in order to prevent the extinction of most of our plants and animals, we must first understand what creates and maintains diversity,” he says. Problems for biodiversity started when humans began destroying the diverse forests and grasslands that once covered the continent. Well over 70% of the forests along the eastern seaboard are gone. The habitat patches remaining are too small to sustain populations of most living things for very long. Habitat fragmentation leads to local extinction over time. “The number of species that will survive human habitat destruction is a simple percentage of the amount of habitat we leave undisturbed: a 1:1 ratio.”
Today 83% of our 300 million people live in cities and/or sprawling suburbs. By 1986, over 69 million acres had been converted to urban/suburban landscapes. We have paved 4 million linear miles of public roads; add to that parking lots, driveways, and other paved surfaces = 43,480 square miles of blacktop on the landscape. We have converted between nearly 40 million acres, or 62,500 square miles, to suburban lawns. Only 3 to 5% of the land remains undisturbed habitat for plants and animals.
Habitat loss has put birds under siege around the globe. We are losing birds because we have taken away their homes and food and replaced them with dangerous obstacles, like roads and buildings that take a huge toll.
“Unless we modify the places we live, work, and play to meet not only our needs, but also the needs of other species, nearly all species of native wildlife will disappear forever.” Most species could live with humans if their basic ecological needs were met. We have excluded other species from our living spaces through thoughtlessness (and ignorance), not through need.
Who cares about biodiversity? We all should; we need biodiversity because it literally sustains us. Biodiversity is essential to the stability – the very existence – of ecosystems. We remove species from ecosystems at the risk of their complete collapse. Biodiversity also plays an important role in the efficiency with which ecosystems function. Energy flowing though ecosystems with many types of species is used more efficiently, with less loss to the surrounding environment. More energy in a system means it will be more productive. But the benefits of diversity are not realized unless the species are all functioning members of an interacting community, measured by what a species is contributing to the ecosystem. Diversity is important when the species are contributing members of their ecosystem, and this is most likely when species have evolved together over long periods of time. Biodiversity is a national treasure that we have abused terribly, mainly because we do not understand the consequences of habitat and ecosystem destruction.
Tallamy explains why insects can’t eat most of the alien plants that we put in our yards, around our homes. Mainly, the plants and insects haven’t evolved together for insects to adapt to the specific chemical mix that characterizes different plants. Most phytophagous insect species are able to eat only vegetation from plants with which they share an evolutionary history. By definition, native insects have not shared evolutionary history with alien plants. Tallamy’s research has found that “native plants produce 4 times more herbivore biomass than alien species and support 3.2 times as many herbivore species.”
So how do we know what is native and what is not? The key factor is coevolving. “A plant can only function as a true native if it is interacting with and contributing to the community that historically helped shape it.”
Moreover, alien plants often harbor diseases to which they are resistant, but can literally wipe out native species. An example is the American chestnut tree, wiped out by the chestnut blight. Alien plants beget alien insects that include serious pests like Japanese beetles, cottony cushion scale, hemlock wooly adelgid, and balsam wooly adelgid.
These are serious threats to our gardens and agriculture! Tallamy argues that it is simply impossible to import alien nursery stock without bringing in foreign disease and insect pests, no matter how much regulation we establish. Plus the alien plants we put in our gardens are often dispersed to other areas, where they become “invasive species.” Alien ornamentals are particularly good at outcompeting native vegetation. A “pest free” plant is inherently unpalatable to insects and thus makes no contribution to the food chain and does not become a functioning member of the ecosystem in which it is planted.
A healthy ecosystem is a collection of plants and animals – producers and consumers – that are in balance. In a balanced community, no one member of the food chain dominates another. Ironically, a sterile garden is teetering on the brink of destruction because it cannot function as a dynamic community of interacting organisms, all working smoothly to perpetuate their interactions. Its checks and balances are gone.
Self-sustaining balance in garden communities is only achieved through complexity, and redundancy. That’s why monocultures in agricultural plantings are so notoriously unstable. A study by Shrewsbury and Raupp at the University of Maryland showed how increasing the diversity of plants in suburban landscapes can keep pest populations in check without the use of pesticides. Tallamy describes the example of his neighbor’s horse barn that outputs enough manure to produce an abundance of house flies. When once Tallamy’s home was overrun by house flies, now he rarely sees them. “Our neighbor’s barn still churns out houseflies by the millions, but now, almost all are eaten by predators whose populations have caught up with them.” This happens because the diverse native plantings in his yard attract a diversity of fly predators. “Many flies are picked off in flight before they reach our house by the tree swallows that nest in our bluebird boxes. Others are eaten by spider and insect predators that are numerous to do the job.”
There is no inherent conflict between creating a beautiful garden and establishing a functioning, sustainable garden ecosystem. “The decision to garden with native plants to improve the resource base for wildlife need not be unpleasant medicine.” Your departure from traditional landscape designs can be compatible with your neighbors and you can create more densely planted gardens. Most people start small, usually with a butterfly garden, and are amazed and delighted to watch the variety of caterpillars and butterflies that adorn their garden. Ultimately, this paradigm shift in gardening will mean more enjoyment and less maintenance of your habitat as the diversity of plants and wildlife become self-sustaining. But there’s just one caveat: you will still be battling the invasion of alien species that, if left unchecked, can dominate an area, choking out native plants and disrupting the balance.
Tired of raking and bagging all those leaves in the fall? “We lose much when we remove leaf litter because it provides so many free services for us: free mulch, free fertilizer, free weed control, and free soil amendments. Litter provides habitat for many arthropod predators that help keep garden communities ecologically balanced. A deep bed of leaf litter acts like a sponge, soaking up enormous quantities of rain water and preventing heavy runoff that contributes to flooding. After the rain stops, leaf litter slowly releases its moisture, keeping plants and trees in your garden well hydrated, even during dry periods.”
“Knowledge is power! Understand how important natives are to sustaining biodiversity, and that adding plant biomass and diversity to your property is the key to supporting local wildlife. Humans cannot exist for very long on this earth without the support of healthy ecosystems. Most people, through no fault of their own, are so divorced from nature in their education and their everyday lives that they do not know what nature is, why we need it, or in what ways it is wonderful!” Humans can do much to end the extinction crisis. The more natives you incorporate into your yard/garden, the more and happier will be the creatures in your neighborhood – including you!
Tallamy includes chapters with stunning color photos of “what bird food looks like” and a detailed list of recommended plantings for your yard/garden. The book is both an enlightening eye-opener about the importance of the natural world, as well as a reference guide you can frequent as you develop a plan for your native garden. This is a must read for everyone!
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