BOOK REVIEW
Bringing Nature Home
by Douglas W. Tallamy
Once in a great long while you read a book that gives you a whole new understanding or paradigm shift in your perspective. For me, this is that book. In the words of Rick Darke, from the Foreword:
…Tallamy recognizes the changing dynamics of our world and suggests how individual gardeners, collectively, can protect and conserve the local biological diversity that is truly vital and irreplaceable. (Rick Darke, foreword)
Yes. Wow. That is powerful. Here’s the Thesis of the book:
In modern city and suburban residential areas, the ideal yard is a lawn with foundation plantings and a couple of trees. What has been created with this ideal are “food deserts” for the lowest members of the food chain, the caterpillars and other tiny critters that feed the birds, frogs, and other small wildlife. Every individual gardener in America has the power to change that. This book aims to convince us all to act now to protect biodiversity in our world.
We gardeners love our yards. We search high and low for plants to add to our collections, write down the names of something we saw at a botanic garden, with hopes that it will grow well in our area. Many of the plants we are drawn to are not native to our area. Tallamy calls these non-native plants “alien” plants. They may not be invasive, and may be quite popular and beautiful. The problem is this. In an ecological context, they are alien to the native animal life forms that depend on the plants around them to survive.
Early in the book entomologist Douglas Tallamy explains how he came to be a crusader for native plants, after he and his wife moved to 10 acres that was 35% covered in aggressive plant species from other continents.
“… Early on in my assault on the aliens in my own yard, I noticed a rather striking pattern. The alien plants that were taking over the land, all had very little or no leaf damage from insects, while the native species had obviously supplied many insects with food. If our native insect fauna cannot, or will not, use alien plants for food, then insect populations in areas with many alien plants will be smaller than insect populations in areas with all natives. This may sound like a gardener’s dream: a land without insects! But because so many animals depend partially or entirely on insect protein for food, a land without insects is a land without most forms of higher life (Wilson 1987). “
Tallamy’s argument for using native plant species moves beyond debatable values and ethics into the world of scientific fact. We can no longer hope to coexist with other animals if we continue to wage war on their homes and food supplies. This simple tenet provides an imperative, particularly for the bird and butterfly lovers among us: to fight invasive aliens as if it really matters and to reevaluate our centuries-old love affair with alien ornamentals.
A plant that has fed nothing has not done its job.
Somehow, along the way, we have come to expect perfection in our gardens (think of the large, artificially bright flowers now seen as normal & healthy). Rather, they are a clear sign of a garden so contrived that it is no longer a living community, so unbalanced that any life form other than the desired plants is viewed as an enemy and quickly eliminated. Ironically, a sterile garden is one teetering on the brink of destruction. It can no longer function as a dynamic part of the community of interacting organisms, all working smoothly to perpetuate their interactions. Its checks and balances are gone.
Why do we need biodiversity?
We need redundancy in our ecology. “…In a diverse ecosystem, many species perform similar tasks. Penstemon flowers, for instance, might be visited by 3 species of bumblebees, five species of moths, and one hummingbird species. If one or two of those pollinators disappear, the plants will still be pollinated and make viable seeds. The rodents that eat those seeds will still have food, as will the screech owls that eat the rodents. Redundancy in pollinators will save the day. But if the ecosystem is depauperate in pollinating species, the loss of one pollinator might quickly lead to the local extinction of the penstemon population. This would not only hurt the rodents and the screech owls, but it would also lead to the extinction of all the insects that eat only penstemon leaves. These losses would then reduce the food available for all insectivores that included those insect specialists in their own diets. If this food reduction were large enough, insectivorous birds that bred in the area would not be able to feed their young, and they too would be lost from the ecosystem. These types of connections are not far-fetched; they are common in all ecosystems.”
Are introduced species good or bad?
Why, if diversity is such a good thing, is everyone so concerned about the addition of species that evolved elsewhere. Good question which scientists are still debating. To date, some 50,000 alien species of plants and animals have colonized North America. Not all are “invasive”. If you simply count numbers of species, the introduction of an “alien” increases the biodiversity by one, doesn’t it? Not so fast. Here is an example: The invasion of the Florida Everglades by Melaleucca quinquenervia, the paperbark tea tree. It was imported in 1906 as an ornamental tree. It is highly adaptable and can grow well in either dry soil or standing water. When humans lowered the water table in much of the Everglades, Melaleuca quickly invaded, almost completely displacing native grasses on hundreds of thousands of acres.
The treasured “River of Grass” has become a dense forest of alien trees that are completely useless to the creatures of the Everglades. What is Melaleuca failing to contribute to the Everglades ecosystem, compared to the grasses it has displaced? It has transformed the sunny wet grasslands into deeply shaded, drier forests dominated by a single species. The grassland birds that breed in the Everglades cannot nest in the trees. They find fewer insects to eat because native insects cannot eat Melaleuca leaves. Alligators cannot make their wallows or find food in Melaleuca groves, and so they have lost hundreds of thousands of acres of habitat. Butterflies cannot find their host plants, egrets cannot hunt the fish they eat, and hummingbirds cannot find the nectar they need to survive from day to day. Even though the number of plant species present in the area is higher by one, the ecological interactions that drive the Everglades ecosystem have collapsed where Melaleuca has invaded because its dominance contributes nothing to other organisms. Diversity is important, then, only when the species that can be said to create it are contributing members of their ecosystem. This contribution is most likely when species have evolved together over long periods of time.
Why can’t Insects Eat Alien Plants?
Mainly 3 reasons: One, pest-free ornamentals are favored for importation (considered a “desirable characteristic” by horticulturists); two, the pace of adaptation is very slow; and three, most insects are specialists. The fact that we have so many “aliens” in our midst provides the perfect opportunity for measuring how long it takes native insects to adopt alien plants as hosts…. For example, the Eurasian genotype Phragmites australis supports over 170 species of insects, while only 5 species of our native herbivores use this plant in North America. The Melaleuca tea tree from Australia is host to 409 arthropods in its native setting, where in Florida, only 8 species of arthropods have been recorded eating the leaves here.
These are not isolated instances. We have enough research now recorded to see that this is true for every alien plant we’ve examined.
Creating Balanced Communities
“My message in this book is a simple one. By favoring native plants over aliens in the suburban landscape, gardeners can do much to sustain the biodiversity that has been one of this country’s richest assets. … People see a disconnect between the typical goals of a gardener (to grow beautiful, undamaged plants), and my suggestion to use gardens to produce lots of insects. Yikes! Am I crazy? Maybe just a little, but not because I want suburbia to do a better job supporting the natural world. The natural world is both beautiful and full of life. Why shouldn’t our gardens reflect that?”
Furthermore:
“In an effort to create gardens free of insect problems, most gardeners have used a recipe perfect for cooking up insect outbreaks: alien plants, lack of plant diversity, and insecticides. Would we not better achieve our goal of a pest-free garden if we employed nature herself to look after things? We have spent the last half-century proving beyond the shadow of a doubt that a sterile garden does not work. It is a high input enterprise requiring more time and money than most of us would like, or are able, to devote or spend…”
“ Sarah Stein, renowned for her foresight regarding the role gardens will have to play in future conservation efforts, recognized this years ago. She minced no words when talking about the effects of suburban landscapes on the natural world: You can’t run a supermarket on just bread, and you can’t run an ecosystem on just lawn. Lawns and foundation plantings are a lot simpler than the wild, diverse landscapes they replace.”
The switch requires a change in mindset. When I see that a little critter has feasted on some leaves, it now makes me smile to know that my choice of plant has provided sustenance for a tiny creature that then has provided sustenance for something a little bigger. You know, the food chain. Tallamy has a “10-step plan” for those that are bothered by the nibbled leaves. When you see the devoured leaves, turn around and take 10 steps back. Then, look again and all is well.
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A good place to stop with this book review comes at the end of Chapter 9, page 119:
“I could go on for pages describing the unparalleled diversity of insect life that will become an integral part of your garden when you include native host plants in your garden design. If you take the time to enter their world, even for a little while, these tiny marvels will not only enrich your garden, they will enrich your life as well.”
Indeed, Tallamy does go on for “pages and pages” – more than 200 more! I could not put the book down once I started reading it. The message is profound and the writing is clear and witty. This book has a big idea backed up with research and followed with in-depth Appendices of native plants by region, host plants to butterflies and showy moths, and research. If you have an interest in learning more, read it in full – take notes, make lists, change the world.