GARDENING FOR LIFE - DOUG TALLAMY
Chances are, you have never thought of your garden - - indeed, of all of the space on your property - - as a wildlife preserve that represents the last opportunity we have for sustaining plants and animals that were once common throughout the U.S. But that is exactly the role that built landscapes are now playing and will play even more in the near future. If this is news to you, it’s not your fault. We were taught from childhood that plants are decorations and our landscapes are for beauty; they are an outlet for expressing our artistic talents and an oasis for having fun and relaxing in. And, whether we like it or not, the way we landscape our properties is taken by our neighbors as a statement of our wealth, our social status, and our willingness to follow cultural norms.
But no one has taught us that we have forced the plants and animals that evolved in North America (our nation’s biodiversity) to depend more and more on human-dominated landscapes for their continued existence. We have always thought that biodiversity was happy somewhere “out there, in nature,” in our local woodlot or perhaps our state and national parks. We have heard little about the rate at which species are disappearing from our neighborhoods, towns, counties, and states. Even worse, we have never been taught how vital biodiversity is for our own well-being.
We Have Taken It All
The population of the U.S., now over 330 million people, has more than doubled since most of us were kids, and it continues to grow by 4800 people each day. All of those additional souls, together with cheap gas, our love affair with the car, and our quest to own ever larger homes, have fueled unprecedented development that continues to sprawl over 2 million additional acres per year (the size of Yellowstone National Park). The Chesapeake Bay watershed has lost 100 acres of forest each day since 1985. We have connected all of our developments with 4 million miles of roads, and their combined paved surface is nearly five times the size of New Jersey. Somewhere along the way we decided to convert most of our living and working spaces into huge expanses of lawn. So far, we have planted over 62,500 square miles -some 40 million acres - in lawn. Each weekend we mow an area the size of New England to within one inch and then congratulate ourselves on a job well done. And it’s not as though those little woodlots and “open spaces” we have not paved or manicured are pristine. Nearly all are second-growth forests that have been overtaken by invasive Asian plants like autumn olive, multiflora rose, Oriental bittersweet, porcelainberry, buckthorn, privet, and bush honeysuckle.
To nature lovers, these are horrifying statistics. I stress them so that we can clearly understand the challenge before us. We have turned 54% of the lower 48 states into a matrix of cities, suburbs, roads, airports, power and pipelines, shopping centers, golf courses, infrastructure, and isolated habitat fragments, with 41% more of the U.S. into various forms of agriculture. That’s right: we humans have taken 95% of the natural world and made it unnatural. But does this matter? Are there consequences to using almost all of our land to meet human needs without considering the needs of other species? Absolutely, both for biodiversity and for us. Our fellow creatures need food and shelter to survive and reproduce, and we need robust populations of our fellow creatures because they are what run the ecosystems on which we all depend. Although we like nature, we have always felt apart from it; humans are here and nature is someplace else. The idea that we could coexist in the same place at the same time has never been part of the vast Western or Asian cultures.
Why We Need Biodiversity
For most of us, hearing such numbers triggers a passing sadness, but few people feel personally threatened by the loss of biodiversity. Here’s why you should. Biodiversity losses are a clear sign that our own life-support systems are failing. The ecosystems that determine the earth’s ability to support us are run by the plants and animals around us. It is plants that generate oxygen and clean water, that create topsoil out of rock, and that buffer extreme weather events like droughts and floods. It is insect decomposers that drive the nutrient cycles on earth, allowing each new generation of plants and animals to exist. It is pollinators that are essential to the continued existence of 80 % of all plants and 90% of all flowering plants, and it is birds and mammals that disperse the seeds of those plants and provide them with pest control services.
And now, with human-induced climate change threatening the planet, it is plants that will suck much of that excess carbon out of the air, build their tissues with it, and pump the surplus into the soil for long-term storage - if we would only put them back into our landscapes. Humans cannot live as the only species on this planet because it is other species that create the ecosystem services essential to us. Every time we force a species to extinction, we are encouraging our own demise. Despite the disdain with which we have treated it in the past, biodiversity is not optional.
Parks Are Not Enough
I am often asked why the habitats we have preserved within our park system are not enough to save most species from extinction. Years of research by evolutionary biologists have shown that the area required to sustain biodiversity is pretty much the same as the area required to generate it in the first place. The consequences of this simple relationship are profound. Since we have usurped 95% of the lower 48’s natural areas, we can expect to lose 95% of the species that once lived there unless we learn how to share our living, working, and agricultural spaces with biodiversity. And studies of habitat islands with known histories, such as Barro Colorado Island in the Panama Canal and Ashdown Forest in England, have so far shown these predictions to be accurate. Species are lost at the same proportion with which a habitat is reduced in size. The good news is that extinction takes a while, so if we start sharing our landscapes with other living things, we should be able to save much of the biodiversity that still exists.
Plant Choice Matters
What will it take to give our local animals what they need to survive and reproduce on our properties? Native plants - and lots of them. This is a scientific fact deduced from thousands of studies about how energy moves through food webs. The general reasoning goes something like this: All animals get their energy directly from plants, or by eating something that has already eaten a plant. The group of animals most responsible for passing energy from plants to the animals that can’t eat plants is insects. This is what makes insects such vital components of healthy ecosystems. So many animals depend on insects for food (e.g., spiders, reptiles and amphibians, rodents, 96% of all terrestrial birds) that removing insects from a food web spells its doom.
But that is exactly what we are doing in our landscapes. For over a century we have favored ornamental plants from Asia, Europe, and South America over those that have evolved right here. If all plants were created equal, that would be fine. But every plant species protects its leaves with a species-specific mixture of nasty chemicals. With few exceptions, only insect species that have shared a long evolutionary history with a particular plant lineage have developed the physiological adaptations required to digest the chemicals in their host’s leaves. They have specialized over time to eat only the plants sharing those particular chemicals. When we present insects from Pennsylvania with plants that evolved on another continent, chances are those insects will be unable to eat them.
We used to think this was good. Use “pest free” plants, and our insects will disappear! But an insect that cannot eat part of a leaf cannot fulfill its role in the food web. We have planted Kousa dogwood, a species from China that supports no insect herbivores, instead of our native flowering dogwood (Cornus florida) that supports 117 species of moths and butterflies alone. On hundreds of thousands of acres we have planted Asian goldenraintrees, ginkgos, burning bushes, barberries, autumn olives, privets, bush honeysuckles, Callery pears, Miscanthus, and dozens of other foreign ornamentals instead of our beautiful oaks, hickories, cherries, basswoods, elms, and others, and we have thereby lost the chance to support thousands of species of caterpillars, the most nutritious bird food available.
My research has shown that non-native ornamentals support 29 times less animal diversity than do native ornamentals. And when these same ornamentals escape our gardens and run amuck in our natural areas, they reduce insect biomass by 96%.
In the past we designed landscapes as if they weren’t essential parts of our local ecosystems. But if your yard, your neighbor’s yard, your entire neighborhood and township, in fact, all the places in which we live, work, and play, are excused from contributing to our local ecosystems, then the natural world that supports us is whittled down to nonfunctional remnants of its former self. This must change if we hope to avoid the worst of Earth’s sixth mass extinction and to sustain the production of essential ecosystem services. Everyone who owns land has a golden opportunity to enhance, rather than degrade, local ecosystems by including ecological function as a criterion when we choose landscape plants. And everyone who does not own land can become a player in the future of conservation by volunteering for a local park or land conservancy.
The four ecological functions that all landscapes need to perform are: 1) support a diverse and complex food web; 2) manage local watersheds; 3) move carbon from the atmosphere to the soil; and, 4) provide food and housing for as many species of native bees as possible. Lawn does none of these things well, so reducing the area we have in turf grass is a logical first step. But plants vary a great deal in how well they achieve ecological goals, so we must choose very carefully the plants we use to replace lawn. A handy tool to do just that can be found on the National Wildlife Federation website. Select ‘Native Plant Finder’ and enter your zip code; a ranked list of ecologically-productive woody and herbaceous plants for your county will pop up.
Not in Our Yard!
Recently the World Wildlife Fund reported that Planet Earth has lost two-thirds of its wildlife since 1970. This jaw-dropping news joins a litany of recent reports about the decline of insects globally, the loss of three billion North American birds, the failure of the 150-nation global biodiversity initiative to meet any of its ten-year goals, and the prediction by the U.N. that one million species will go extinct in the next twenty years. Yet to those who justifiably conclude that the demise of our fellow earthlings is inevitable, I say “Not in our yard!!”
Mention “wildlife,” and most people conjure up images of charismatic megafauna like lions and tigers and bears (oh my!). But wildlife is far more than the few large mammal species that adorned our childhood picture books. The vast majority of earth’s animal species are insects, and we can’t live without them. As E.O. Wilson famously explained long ago, insects are the little things that run the world. Without insect pollinators, 80% of all plants and 90% of all flowering plants would disappear, as would the food webs that support mammals, reptiles, amphibians, birds, and freshwater fishes. Wilson’s message was clear: there will be no lions, tigers, or bears, birds, bats, or bunnies - or humans - in a world without insects.
For the past four years I have been photographing the moth species that live on our property. This year I reached 1,028 species. That’s right: at least 1,028 (and counting) moth species make their living on our ten-acre patch of southeastern Pennsylvania. That is 40% of all of the moth species that have been recorded in the 2.4 million acres that comprise Pennsylvania; 40% on just 1/240,000th of the land area!
And because each of those moths, and the caterpillars they developed from, are essential “bird food,” 59 species of birds have been able to breed on our property, a full 38 % of all the terrestrial birds that breed in Pennsylvania. And who knows how many additional bird species have used our land as a refueling site during fall and spring migration?
Our property is not a preserve that has been protected for a century. Just the opposite. Not long ago, it was part of a farm whose successive owners had worked the land hard for 300 years. Before we moved in, the vegetation was a tangle of invasive Asian plants that the owners had mowed for hay. Very few trees and native shrubs grew here, and most of the resident birds were invasive starlings and house sparrows that could thrive on exhausted farmland. The caterpillars that sustain 96% of North American terrestrial bird species were largely absent.
But today, rather than having lost two-thirds of its wildlife, our ten acres have increased the number of its resident species by at least that much. The depleted agricultural wasteland of two decades ago has become a hotspot for local wildlife. How did this happen?
The seemingly astounding rebound in species on our property was neither astounding nor accidental. It was a predictable response by the natural world to our purposefully restoring nature’s foundation: native plants. The moths I am counting have returned because the native plants they require are here as well. And those plants are thriving on our property because, along with the wind and the local blue jays, we have planted them. We also have removed the tangle of invasive species so our native plants have enough space, light, and water to grow. The birds and other vertebrates that live on our land can do so, not just because of the moths our plants produce, but also because of the fruits and nuts our oaks, black walnuts, hickories, filberts, blackberries, serviceberries, dogwoods, persimmons, black cherries, pawpaws, chokeberries, viburnums, and black gums make each year. Winter birds like juncos and white-throated sparrows migrate to our yard because of the copious amounts of seeds produced by our native grasses, sweetgums, sycamores, evening primroses, asters, wild lettuce, black-eyed Susan’s, and goldenrods. Red-shouldered hawks, Cooper’s hawks, and sharp-shinned hawks regularly hunt here because their prey is abundant. And it is hard to walk anywhere without encountering the cutest little gray tree frogs imaginable.
Will our ten-acre restoration alone be able to reverse global declines in wildlife? Of course not, but if ecologically-appropriate plant choices were consistently made by homeowners, land managers, and municipalities everywhere, the habitat value of all non-agricultural land would be measurably enhanced, just as it has been on our landscape in Pennsylvania. Aided by groups like the National Wildlife Federation, National Audubon, Wild Ones, Grow Native Massachusetts, the Missouri Prairie Foundation, and the California Native Plant Society, such transformations are well underway across the country, and the results are beginning to defy global wildlife trends. Returning native plants to our landscapes provides essential energy for species-rich food webs on any scale, whether they are ten-acre parcels like ours in Pennsylvania, half-acre suburban lots like Margy and Dan Terpstra’s near St. Louis (https://hummerhavenunltd.com/blog?first=289339031), 1/10th-acre city lots like Pam Karlson’s in Chicago (https://www.nachicago.com/2020/05/29/316242/bird-friendly-gardens), or even the three-foot-wide strip of nature along Manhattan’s High Line (https://www.thehighline.org/blog/2019/04/23/habitat-in-the-sky-studying-wild-bees-on-the-high-line-with-the-american-museum-of-natural-history/).
You Are Nature’s Best Hope
The United Nations designates Biosphere Reserves as places of “ecological significance.” That language has always bothered me because it suggests that there are places on earth without ecological significance. Not so! Every square inch of planet earth has ecological significance, even where we live, work, and play. If we landscape these areas with plant function as well as aesthetics in mind, we can create viable habitat where humans are, not just where humans are not. We must rethink the importance of conserving our fellow earthlings and the ecosystems they depend on. In the past we have treated them as if they were optional: enhancements that we like but do not really need. But nature is not something we should preserve just for the enjoyment of future generations; it is something we must preserve so that we have future generations.
Somewhere along the line we assigned earth stewardship to just a few specialists: a few ecologists and conservation biologists. The rest of us have had cultural permission to destroy the natural world whenever and wherever we wanted, using oxymoronic words like ‘development’ and ‘progress’ as rationalizations. This makes no sense; every human being on earth depends entirely on the quality of earth’s ecosystems, so why wouldn’t every one of us bear the responsibility of good earth stewardship?
The ecological approach to landscaping that I have described here is nothing more than basic earth stewardship, but it is stewardship that empowers us all to become forces in conservation. Today’s environmental challenges are so enormous that it is easy to feel helpless, as if one person can’t make a difference - despite the cliché that suggests you can. In this case, however, the cliché is right on: by choosing ecologically-effective plants for your landscape, by shrinking your lawn, and by removing your invasive ornamentals – all actions a single person can take - you will be able to make a difference that you can see, and enjoy, almost immediately. Life will return to your property!
Even if you don’t own land, you can make a difference by volunteering to help your local land conservancy manage its properties, or simply by helping someone who does own property. Either as property owners or volunteers, each of us has the power - and we clearly have the responsibility - to enhance the ecological value of local landscapes. Whether we decide to do so will determine nature’s fate and, ultimately, our own. In that sense, we all are nature’s best hope!