The Natives versus Exotics Debate
First, a word on terminology. The term invasive is emotionally loaded with negative connotations. The term implies that a species by itself can invade, yet
the ability to invade is not held by any one species. Whether an organism can invade a new landscape depends on the interaction between it and its
environment, both living and inanimate. Dropped into one new home, a species may thrive; in another it may fail utterly. Calling a species “invasive” is not
good science. Following David Jacke in his book, Edible Forest Gardens, I will use the word opportunistic, which more accurately gives the sense that a
species needs particular conditions to behave as it does. Many unruly exotic species are insipidly tame in their home habitat. Even the words native and
exotic have their difficulties, although I continue to use them. Does exotic mean a species wasn’t here before you got here, or before the first botanist did,
before Columbus, the first human, or what? Species are constantly in motion. We need to rethink these words and why we use them.
Gardening with native plants has become not merely popular in recent years, it’s become a cause célèbre. Supporters of natural gardening can
become quite exercised when someone recommends nonnative plants. Governments, agribusinesses, and conservation groups have spent millions of
dollars trying to eradicate “exotic” species. Parks departments across the nation have enacted native-only policies for trails, playgrounds, and other public
places. The arguments for natives have merit: of course we want to preserve our native species and their habitat. But much of the energy spent on
yanking exotics and planting natives is misdirected and futile, evidenced by the failure of so many restoration projects in which the nonnatives quietly
reestablish after the funding or labor pool runs out. Without major changes in our land-use practices, the campaign to eradicate exotic plants approaches
futility. A little ecological knowledge shows why. Look at most opportunistic plants. European bittersweet and Japanese honeysuckle swarm over New
England’s forest margins. Kudzu chokes the roadsides and forest edges in the South. Purple loosestrife sweeps across the waterways of both coasts
and the Midwest, and Russian olive springs up as small forests in the West. In nearly every case, these plants are invading disturbed land and disrupted
ecosystems, fragmented and degraded by grazing, logging, dams, road building, pollution, and other human activity. Less-disturbed ecosystems are
much more resistant to opportunistic species, though opportunists can move into them if they establish at entry points such as road cuts and logging sites.
One pro-native garden writer describes what he calls “the kudzu phenomenon, where an exotic displaces natives unless we constantly intervene.” But
our intervention is the problem. We assume nature is making a mistake when it creates hybrid, fast-healing thickets, so rather than allowing disturbed
habitat to stabilize, we keep disturbing it. We can spray and uproot bittersweet and honeysuckle all we want, but they’ll come right back. These are
species that love sunlit edges, and we’ve carved forests into countless tiny pieces that have more edge than interior, creating perfect habitat for these
exotics. The same goes for kudzu, loosestrife, and nearly all the rest. In the East, purple loosestrife followed the nineteenth-century canals into wetlands;
and in the West it has barreled down irrigation ditches into marshland and ponds. Humans create perfect conditions for exotics to thrive. I’ve often heard
blame put on one or another opportunistic species when a native species goes locally extinct. That’s understandable. When we lose something we love,
we search for a scapegoat, and a newly arrived species makes a ready target. But virtually every time I’ve examined that charge, it turns out that the place
had first been severely disturbed by development, logging, or other human use. The opportunist moved in after the primary damage was done and often in
direct response to it.
Opportunistic plants crave disturbance, and they love edges. Those are two things development spawns in huge quantity. Unless we stop creating edge
and disturbance, our eradication efforts will be in vain, except in tiny patches. The best long-term hope for eliminating most opportunistic species lies in
avoiding soil disturbance, restoring intact forest, and shading the newcomers out with other species. In other words, we need to create landscapes that
are more ecologically mature. Opportunistic plants are, with a few exceptions such as English ivy, almost exclusively pioneer species that need sunlight,
churned-up ground, and, often, poor soil. For example, kudzu, Scot’s broom, and Russian olive are nitrogen fixers whose role is to build soil fertility. So
they prosper in farmed-out fields and overgrazed rangeland and are nature’s way of rebuilding fertility with what is available.
Here’s why opportunistic plants are so successful. When we clear land or carve a forest into fragments, we’re creating lots of open niches. All that sunny
space and bare soil is just crying out to be colonized by light- and fertility-absorbing green matter. Nature will quickly conjure up as much biomass as
possible to capture the bounty, by seeding low-growing “weeds” into a clearing or, better yet, sprouting a tall thicket stretching into all three dimensions to
more effectively absorb light and develop deep roots. That’s why forest margins are often an impenetrable tangle of shrubs, vines, and small trees: there’s
plenty of light to harvest. Just inside the edge, though, where there is less light and little disturbance, forests are usually open and spacious.
When humans make a clearing, nature leaps in, working furiously to rebuild an intact humus and fungal layer, harvest energy, and reconstruct all the
cycles and connections that have been severed. A thicket of fast-growing pioneer plants, packing a lot of biomass into a small space, is a very effective
way to do this. Permaculture’s cooriginator, David Holmgren, calls these rampantly growing blends of natives and exotics “recombinant ecologies” and
believes that they are nature’s effective strategy of assembling available plants to heal damaged land. Current research is showing the value and healing
power of these new ecologies. If we clear out the thicket in the misguided belief that meadows should forever remain meadows even under heavy
irrigation, or that all forest edges should have tidy, open understories, we are just setting the recovery process back. Nature will then relentlessly return to
work, filling in with pioneer plants again. And she doesn’t care if a nitrogen fixer or a soil-stabilizing plant arrived via continental drift or a bulldozer’s
treads, as long as it can quickly stitch a functioning ecosystem together.
The sharply logged edge of a woodland abutted by a lawn or field—so common in suburbs—is a perfect home for sun-loving exotics. If we plant low
trees and shrubs to soften these margins, thus swallowing up the sunlight that pierces the forest edges, the niche for the opportunist will disappear. Simply
removing the exotic won’t do much good except in a highly managed yard. The plant will come right back into the perfect habitat that waits for it. That’s
one reason that herbicide manufacturers are helping fund the campaign for native plants. They know a repeat customer when they see one. Nature abhors
a vacuum—create one, and she’ll rush in with whatever’s handy. To eradicate opportunists, the habitat for it must be changed into a more mature, less
hospitable landscape. The conditions that support the opportunist must be eliminated.
This approach is far from “live and let live” and more effective than an eternity of weed pulling. Pioneer weedscapes may be nature’s way, but most
people don’t want their yard edges to be a tangled thicket. Yards can be kept free from opportunists, particularly in small spaces and if we’re willing to be
persistent for several seasons. But it’s hard to succeed when we’re stuck on the old “clear, spray, and curse” treadmill. An easier and more productive
strategy is to learn from the more mature forest edges near us. Again, observing nature can teach us what species naturally nestle into the sunny margins
of old woods. Look at these places, and you may find dogwood, cherry, crabapple, alder, or small varieties of maple. The species vary around the country,
but edge-loving trees and shrubs are good candidates for jump-starting a yard or wood-lot margin toward a more mature ecological phase. Plant them at
those overgrown woody edges to fill in the gaps before something you don’t want takes hold. You can’t fight nature—nature always bats last—but you can
sometimes be first to get where it’s going.
The nineteenth-century scientist Thomas Henry Huxley likened nature to a brilliant opponent in chess: “We know that his play is always fair, just, and
patient. But also we know, to our cost, that he never overlooks a mistake, or makes the smallest allowance for ignorance.” Nature has a patience that
humans lack. We may uproot some bittersweet or kudzu for a few seasons, but nature will keep reseeding it, year in, year out, waiting until we tire of the
battle. Nature takes the long view.
It is only our limited time frame that creates the whole “natives versus exotics” controversy. Wind, animals, sea currents, and continental drift have
always dispersed species into new environments. Remember that for millions of years there have been billions of birds, traveling hundreds or thousands
of miles, each with a few seeds in its gut or stuck to the mud on its feet. And each of these many billions of seeds, from thousands of species, is ready to
sprout wherever the bird stops. The planet has been awash in surging, swarming species movements since life began. The fact that it is not one great
homogeneous tangled weed lot is persuasive testimony to the fact that intact ecosystems are very difficult to invade.
Our jet-age mobility has arguably accelerated the movement of species in unnerving and often economically damaging ways. But eventually an
opportunistic species, after a boom-and-bust period, comes into equilibrium with its surroundings. It may take a decade or a century, time spans that
seem like an eternity to a home owner contending with bittersweet or star thistle. But one day the new species becomes “implicated” into the local
ecosystem, developing natural enemies and encountering unwelcome environments that keep it in check.
“Native” is merely a question of perspective: is a species native to this hillside, or this county, the bioregion, continent, or perhaps just to this planet? I
see a certain irony in immigrant-descended Americans cursing “invasive exotics” for displacing native species. And often an opportunistic species is
playing an important role, where nature is working on a problem that we may not recognize and using the best tools available. For example, purple
loosestrife, perhaps the poster child of exotic-species eradication enthusiasts, turns out to be superb at both tolerating and cleaning up polluted water. It,
like many other opportunistic species, is screaming out to us that there is a problem—contaminated water—and is one of nature’s best agents for solving
the problem by scouring out the pollutants. Also, research is showing that once pollution levels recede to relative cleanliness, the loosestrife dies back.
Other researchers have found that, contrary to assumptions, loosestrife patches support just as many native pollinators and birds as surrounding areas of
native plants. This shows that we need to look deeper into our reasons for demonizing certain species.
Of course, it is foolish to deliberately introduce a species known to be locally opportunistic. Permaculturists use a hierarchy of safety for choosing
plants. First, use a native to fill the desired role if at all possible. If no natives for that niche exist, then use a tested exotic. Only after a great deal of
research would a person then consider a small-scale introduction of a new exotic; and, to be honest, I have never done that, don’t personally know anyone
who has, and don’t recommend it. There are thousands of species that have been tried in many habitats, and if one from that huge assortment won’t work,
perhaps what you have in mind doesn’t need to be done.
I love native plants and grow them whenever appropriate. But nearly the whole issue—from branding certain fast-spreading, soil-building pioneer plants
as evil, to creating the conditions that favor their spread—stems from not understanding nature’s ways. When we think ecologically, the problem either
evaporates as a misunderstanding or reveals solutions inherent in the life cycle of the opportunist. A plant will thrive only if conditions are right for it. Modify
those conditions—eliminate edge, stop disturbing soil, cast shade with trees, clean up pollution—and that opportunist will almost surely cease to be a
I’m also uneasy with the adversarial, polarized relationship with plants that an overzealous enthusiasm for natives can foster. It can result in a “natives
good, everything else bad” frame of mind that heats the gardener’s blood pressure to boiling at the sight of any exotic plant. Rage is not the best emotion
to be carrying into the garden. And we’re all utterly reliant on nonnatives for so many of our needs. Look at our diet. Where did this morning’s breakfast
come from? I’d be surprised if many Americans regularly consume a single plant native to their state. About the only common food crops native to North
America are sunflowers, hops, squash, and some nuts and berries. Nearly everything we eat originated on other continents. Get rid of exotics, and most
of us would be pretty hungry until we learned to prepare local roots, berries, nuts, and greens.
This is why I advocate a sensible balance of native and exotic plants in our landscapes. We may not be able to restore our cities to native wilderness,
but our gardens can play an important role in restoring the functions and services provided by our planet’s environment. A major premise of this book is
that our own yards can allow us to reduce our incessant pressure on the planet’s health. The techniques of permaculture and ecological design allow us to
easily, intelligently, and beautifully provide for some of our own needs. We can create landscapes that behave much like those in nature but tinker with
them just a bit to increase their yield for people while preserving native habitat. And in so doing we can allow some of those factory farms and industrial
forests to revert to wild land.
We have assembled enough knowledge from cultures that live in relative harmony with their environment, and from scientific studies of ecology and
agriculture, to create gardens that offer both habitat to wildlife and support for people. They don’t look like farms. Instead they have the same feel as the
native vegetation but can be tweaked to provide for the needs and interests of the human residents. Picture your favorite natural landscape and then
imagine plucking fruit from the trees, making a crisp salad from the leaves, clipping a bouquet from the abundant flowers, laying in a supply of garden
stakes from a bamboo patch. These gardens tailor a large place for people yet still behave like ecosystems, recycling nutrients, purifying water and air,
offering a home for native and naturalized flora and fauna.
Both natural gardens and ecological gardens emphasize the role of plant communities, that is, groupings of trees, shrubs, and nonwoody plants that
naturally occur together and seem to be connected into a whole. The difference is that natural gardens attempt to mimic native plant communities, while
the gardens in this book combine natives, food plants, medicinal and culinary herbs, insect- and bird-attracting species, plants that build soil, and others
into synergistic, mutually beneficial groupings. These “synthetic” plant communities, which permaculture calls guilds, form healthy, interacting networks
that reduce the gardener’s labor, yield abundant gifts for people and wildlife, and help the environment by restoring nature’s cycles.
Indigenous people, especially those living in the tropics, have been using guilds for millennia to create sustainable landscapes. Only recently have we
understood what they were doing and how they do it. Anthropologists mistook the lush and productive home gardens that enfolded tropical houses for wild
jungle, so perfectly had the inhabitants mimicked the surrounding forest. From these gardeners we’ve learned something about creating landscapes that
work just like nature but offer a role for people.
In temperate climates, the art and science of fashioning communities of useful, attractive plants is a new and vigorous field. Many of the gardeners I
spoke to while researching this book are pioneering these techniques. The last few chapters of this book explain how to design and use guilds to create
vibrant “food forests” and beautiful habitats for people and wildlife. I hope that some who read this book will add to this burgeoning field.
Making the Desert Bloom, Sustainably
To help readers get a feel for an ecological garden, let me describe one of the finest examples I’ve seen. North of Santa Fe, New Mexico, sculptor
Roxanne Swentzell has created an oasis in the high desert she calls Flowering Tree Permaculture Institute.
When I arrived at Flowering Tree, I stepped out of my car and was blasted by the mid-90s heat and the searing glare reflected from the bare, eroded
hillsides nearby. But before me was a wall of greenery, a lush landscape that I’d spotted from at least a mile away, in soothing contrast to the yellow sand
and gravel of the desert.
I entered the yard through a gap between arching trees, and the temperature plummeted. The air here was fresh, cool, and moist, unlike the dusty,
sinus-withering stuff I’d been breathing outside. A canopy of walnut trees, piñon pine, and New Mexico black locust sheltered a lush understory of
pomegranates, nectarines, jujube trees, and almonds. An edible passionflower swarmed up a rock wall. Grapevines arched over an entry trellis. Two
small ponds sparkled with rainwater caught by the adobe house’s roof. Winking brightly from under shrubs and along pathways were endless varieties of
flowers, both native and exotic.
Roxanne, an athletic-looking woman with high, solid cheekbones bequeathed by her Santa Clara forebears, greeted me, smiling at my somewhat
dazed appearance. She’d seen this before, as visitors gawked at the luxuriant growth so dissimilar to the barrenness outside. “We’ve got about 500
species here, on one-eighth acre or so,” she told me. “We’ve tried to make it a self-sufficient place that will take care of us while we take care of it. So we
grow whatever we can that will survive in this climate.”
In 1986 she moved onto a parcel of bare land on the Santa Clara homelands. She describes the place as “no trees, no plants, no animals, just
pounded-down dirt and lots of ants.” She and her two young children built a passive-solar adobe house and began planting. But the climate was too
harsh. Dry winds swept down from the scoured, overgrazed hills and burned up the seedlings, killing those that hadn’t frozen out in winter.
Local permaculture designer Joel Glanzberg entered Roxanne’s life at about this time and helped her ferret out techniques for gardening in the desert.
They dragged in rocks and logs to shade seedlings and dug shallow ditches, called swales, to catch precious rainwater and create sheltered, moist
microclimates. To cast much-needed shade and generate organic matter, Joel and Roxanne planted just about any useful drought-tolerant plant, native or
exotic, that they could find. Thirstier species they located within reach of the asequia, or irrigation ditch, that surged with water once a week by tribal
agreement. Without reliable water, the garden would have been impossible to establish in the desert heat.
They hauled in manure and mulch materials to build rich soil that would hold moisture through drought. Once the hardy young trees and shrubs had
taken hold, they set more delicate plants in their shade. They blended berry bushes and small fruit trees into an edible hedge along the north border, to
offer them food as well as block the winds that roared down the nearby canyon. All these techniques combined into a many-pronged strategy to build
fertile soil, cast shade, damp the wild temperature swings of the desert, and conserve water. Together these practices created a mild, supportive place to
grow a garden. Slowly the barren landscape transformed into a young, multistoried food forest.
Roxanne told me, “The garden was hard to get started, but once the little seedlings took off, then boy, they took off.” At my visit, the landscape was eight
years old, and trees, where none had been before, were as tall as the two-story house. Blessed, cooling shade, from dense to dappled, halted the searing
rays of the sun. Instead of baking the soil, the fierce solar heat was absorbed by the thick leafy canopy and converted into lush greenery, mulch, food, and
deep-questing roots that loosened the soil. In the bright gaps, flowers and food plants vied for sunlight. Even in the shade, a many-layered understory of
shrubs and small trees divided the yard into a path-laced series of small rooms.
Designer Joel Glanzberg stands in a barren desert plot in 1989 at Flowering Tree Permaculture Institute in New Mexico.
I caught glimpses of birds dancing from twig to twig before they disappeared into the shrubbery. A constant rustling and chirping enveloped us on all
sides, and I knew that dozens more birds were hidden in the foliage. Metallic-sheened beneficial wasps dove into the blossoms that surrounded us, and
butterflies of all sizes and colors soared and flapped from flower to leaf. Roxanne carried pruning shears with her as she walked and lopped off the
occasional too-exuberant branch from the mulberries, plums, black locusts, and other vigorously growing trees and shrubs that lined the paths. These
would feed her turkeys or become more mulch.
She pointed out a crimson trumpet-blossomed Penstemon barbatus that looked unhappy in the deep shade. “Things change so fast here,” she said.
“This was in full sun two years ago. Now it’s completely shaded out, and I think it might be rotting from the soil staying too wet. And look at all these
peaches. I better get busy harvesting.”
Four years later, Joel stands in the same spot. An intellligent permaculture design has created a lush oasis around him.
The techniques and design strategies (which this book will describe in detail) had transformed the landscape. Roxanne and her helpers had
rejuvenated a battered plot of desert, created a thick layer of rich soil, and brought immense biodiversity to a once-impoverished place. Here in the high
desert was almost too much water and shade. Food was dropping from the trees faster than they could harvest, and birds that no one had seen for years
were making a home in the yard.
Not everyone begins with as difficult a challenge, as devastated a site, as Roxanne. But there’s quite a gap between the typical yard and what Roxanne
and other similar gardeners have created. The average yard is both an ecological and agricultural desert. The prime offender is short-mown grass, which
offers no habitat and nothing for people except a place to sit, yet sucks down far more water and chemicals than a comparable amount of farmland. The
common, single-function plantings found in most landscapes also have their share of drawbacks. Highly bred flowers, lacking pollen and nectar, displace
bird- and insect-nurturing varieties. Many ornamental plants are no more than pleasant eye candy and could be replaced by equally attractive species that
have uses for people and wildlife.
Typical gardening techniques don’t help much, either. A tidy layer of bark mulch, instead of more natural and protective ground plants, robs small
animals and insects of their homes. The heavy chemical use in most lawns, needed because natural soil fertility and insect predators are absent, pollutes
water, kills wildlife, and is almost certainly linked to many ailments. And as mentioned, unproductive home landscapes mask and contribute to the
immense environmental damage our resource consumption does elsewhere, out of sight.
The ecological garden offers a solution. Our yards could be deeply connected to nature yet be more than just wildlife or native plant gardens—they
could link us to nature’s abundance as well. The techniques and strategies to do this have been worked out by resourceful and imaginative pioneers.
These people have mapped a new terrain and brought back what they’ve learned. I spoke to many of them and visited their vibrant, naturally productive
landscapes while researching Gaia’s Garden. These pioneers shared their knowledge, which I have done my best to present in the following pages.
How to Use This Book
Gaia’s Garden is divided into three parts. The rest of Part One continues this introduction to the idea of the garden as an ecosystem. Chapter 2 offers a
simple guide to concepts from ecology that gardeners can apply to make their yards work more like nature. Fear not—this is not a textbook, it’s a
gardening manual, so I don’t go into technical details. I give plenty of practical examples of ecological principles at work. Next, Chapter 3 describes the
design process and techniques that are used to create an ecological garden. Most of these ideas will be familiar to those versed in permaculture, but they
may be new to people from a traditional gardening background.
Moving from theory toward practice, Part Two of the book looks at the pieces of the ecological garden. A chapter each delves into soil (Chapter 4),
water (Chapter 5), plants (Chapter 6), and animals (Chapter 7), but from a different perspective from that of most garden books. Instead of viewing soil,
water, plants, and animals as static, as objects to be manipulated into doing what we want, I treat them as dynamic and constantly evolving, as having
their own qualities that need to be understood to work with them successfully, and as intricately connected to all the other parts of the garden.
Part Three shows how to assemble the garden’s elements into a backyard ecosystem. Chapter 8 begins with simple interplanting techniques and
expands on these to show how to create polycultures (blends of several to many plant species that work together) and human-designed plant
communities, or guilds. Chapter 9 offers several methods for designing garden guilds. Building on these two chapters, Chapter 10 describes how to
assemble plants and guilds into a multistoried food forest or forest garden. Chapter 11 offers strategies and techniques for the special challenges
confronted by city dwellers. The final chapter reveals how these gardens take on a life of their own and mature into self-sustaining miniecosystems that
are far more than the sum of their parts. I also give a few tips and techniques for accelerating this process.
The main text of the book explains the ideas behind an ecological garden and gives examples and descriptions of the ideas in action. Specific garden
techniques are usually set off from the text in boxes so they are easy to find. Included also are lists of plants relevant to the ideas in the text (insect-
attracting species, drought-tolerant plants, and so on), and the appendix contains a large table of useful, multifunctional plants and their characteristics.
Many of the techniques and ideas in this book can be used by themselves, simply as ways to make a conventional garden more productive or Earth
friendly. There’s nothing wrong with taking a mix-and-match approach to these ideas, using only the ones that are easy to fit into an existing landscape.
But these techniques are also synergistic; the more that you put in practice, the more they work together to create a richly connected and complete
landscape that is more than a group of independent parts. These resilient, dynamic backyard ecosystems act like those in nature while providing for us
and reducing our demands on the diminishing resources of this planet.
A Gardener’s Ecology
Something was stealing the Bullock brothers’ food.
Joe, Douglas, and Sam Bullock had moved to Washington’s San Juan Islands in the early 1980s and set to work creating a food forest. They built up
their property’s soil and planted fruit trees, nut trees, and hundreds of other species, all calculated to boost the biological diversity and lushness of this
once-scrubby, blackberry-entangled parcel. A decade later, walnut trees and bamboo groves shaded the paths. Plums, peaches, cherries, and apples
hung in thick festoons from spreading branches, and beneath them flowers, berries, edible greens, and soil-building plants sprawled over every inch of
earth. The Bullocks had created a self-renewing ecosystem that fed their families and visitors, furnished nursery stock for their landscaping business, and
sheltered local wildlife.
One edge of their property bordered a wetland reclaimed a few years before from abandoned farmland. At the marsh’s edge, cattails grew in thick
stands. Young cattail shoots are a delicious wild food, and for several springs and summers the brothers had harvested the baby shoots, steamed or
sautéed them, and added them to meals. But one year they couldn’t find any shoots, only tough mature cattail stalks. Their natural food source had dried
up, and the brothers wanted to know why.
A close look at the marsh revealed that some animal was gnawing the tender shoots off at the waterline. The thieves were thorough. Nothing remained
for the Bullock brothers and their families.
The culprit was quickly spotted. “We’d noticed that as the bog matured and became more productive, the muskrat population was really taking off,”
Douglas Bullock told me. The brothers had built garden beds that extended into the marsh, copying an idea from the ancient Aztecs. They had created
peninsulas by piling straw and branches that reached out like fingers from the shoreline, covered them with rich bog muck, and planted these self-
watering garden beds, called chinampas, with food and wildlife plants. The local animals, already enjoying the new wetland, responded to the enhanced
habitat of the chinampas with explosive breeding. Ducks, kingfishers, herons, and other water birds now abounded, and so did muskrats. “Suddenly the
bog looked like a busy harbor, criss-crossed with muskrat wakes,” Douglas said. Whole flotillas of muskrats were tunneling into the rich soil along the
marsh edge and nibbling down the cattail shoots. The less agile humans couldn’t compete with the industrious rodents.
The brothers lamented the loss of their wild food, yet refused to begin exterminating the culprits. “For one thing, we weren’t going to kill off the wildlife
that we ourselves had attracted,” Douglas explained. “For another, we could have shot muskrats for weeks, and they’d just breed right back again. The
habitat was too good.”
A cattail-less season or two went by. Then, suddenly the tasty shoots were back, and the once-busy “harbor” was more tranquil. The muskrat population
had dwindled. What had happened?
“Otters moved in,” Douglas said. “The muskrats were a great new food source. We’d never seen otters here before. More than otters showed up, too.
We got other predators: bald eagles, hawks, owls. They cleaned up.” Instead of futilely trying to trap the fast-breeding muskrats, the Bullocks sat back and
let nature do the job. The brothers merely provided a rich, diverse habitat where a vigorous food web—one that included predators—could emerge and
right imbalances, such as a horde of ravenous muskrats.
Finding a Niche
Decades before the Bullocks arrived, the lowest part of their property had been wetland. An industrious farmer had diked, drained, and dried up the
“useless” bog and raised crops there for many years. The ecologically oriented Bullocks understood that wetlands, besides being essential for clean
water and wildlife habitat, were some of the most productive ecosystems on the planet, teeming with more plants and animals than any farm. They
decided to restore the wetland and tore out the dikes and drains. Water collected in the low ground, and soon the wetland was back.
While the marsh returned, the Bullocks ferried countless loads of mulch and manure onto their land in their straining pickup truck. The brothers also
forked rich muck from the bog onto the shore, building soil with organic matter and nutrients. In a few years, this tremendous increase in fertility paid off
many times over. Not only could the Bullocks grow more plant varieties than before, but opportunistic wild species could find homes in the enhanced
habitat as well. The combination of water and fertile soil was irresistible.
Some of the earliest new tenants were the cattails. Their seeds may have been brought to the renewed bog by waterfowl, or perhaps they had lain
dormant in the soil for years, hoping for the return of the wetland. In either case, the cattails capitalized on the ripe habitat, busily converting sunlight, water,
and bog muck into fast-growing shoots.
Wherever there is tender greenery, there is someone to consume it—a lesson that gardeners quickly learn when rabbits, field mice, porcupines,
raccoons, and all the rest descend on their vegetables. You can think of this as some horrible corollary of the “Field of Dreams” effect: if you build it, they
will come and eat it; but, in ecologist’s terms, this exemplifies the niche, or role played by each organism. The Bullocks, by creating habitat, opened up an
opportunity for life to exploit. As if being asked to audition for a new role in a play, organisms suited to the job showed up to occupy this new niche. Think
of a niche as a profession and habitat as the work space for performing that job.
As habitat becomes more varied, more niches appear. Often, providing habitat triggers a cascade of niches, which is precisely what we’re trying to do
in the ecological garden. The Bullocks’ place is a good example of a niche cascade. The fertile habitat provided a niche for the cattails, which then
furnished a new food supply that was quickly exploited by muskrats—animals that are custom-made for eating tender shoreline plants. The opportunism
of the muskrats led to both their rise and fall: they fattened happily on the cattails, but that busy harbor of paddling rodents was a beacon for predators. In
the still-wild San Juan Islands, otters sheltered somewhere nearby. Nature’s “grapevine” is fast and effective, and it was only a season or two before the
otters caught wind of the potential harvest and moved in. Just as the cattails had started small, ramped up to thriving numbers, and were chewed down to
a vestige, so too did the muskrats appear, burgeon, and crash in a cycle now interlocked with those of the cattails and otters.
Eventually a form of stability descended on the Bullocks’ land, but it fluctuates now and then as one species or other briefly gains the upper hand and is
then hauled back in line. But, in a place where neither cattails, nor muskrats, nor predators could survive before, all three now thrive, because the Bullocks
provided habitat and soil nutrients. The brothers supplied the beginnings, and nature did the rest. Instead of depleted farmland, the Bullocks and their
friends can admire a verdant, multispecies wetland, rustling with cattails, sedges, willows, and wildflowers, ripe with blueberries and other fruit, filled with
the music of waterfowl and frogs, and offering a glimpse of otters and eagles.
At the Bullock brothers’ farm on Orcas Island in Washington State, an apple tree is surrounded by food- and habitat-creating plants that work together to
benefit both nature and people.
Three Ecological Principles
The Bullocks have built a superb example of ecological gardening, where humans and wildlife can reap the abundance and live in harmony. What
happened on the brothers’ land illustrates several principles of ecology that gardeners can use. The cattail/muskrat/otter progression is a good jumping-
off point to look at three important and related concepts: the niche, succession, and biodiversity. I’ll begin with those and then, throughout this chapter, give
examples of other ecological ideas that can help create sustainable gardens. The ideas presented on the next few pages lay the foundation for the
ecological garden. The examples and techniques given in the rest of this book are grounded in these principles of nature.
Documents you may be interested
Documents you may be interested