5 Bedrock and Baselines

The coming of snowfall: on a day before a full moon, the sky draws close. The ceiling drops, darkening to the color of tarnished silver. By four in the afternoon there are pioneers. Soon they are followed by settlers, which look a little out of place, even lost at first, but not for long. In these first hours, it is just snowfall. By evening it is a storm, gaining strength by the hour. Families count off: two, three, four. Safely home. Overnight, the winds pick up and fall back, like ocean swell. By morning the first act is over, but the drama does not abate. At an hour after sunrise the inside of the house is filled with light. If you are lucky, other than to shovel you will stay in.

Through that day, the sun licks the snow. Not for nothing do chefs and bakers speak of icing, frosting, and glazing. And then, at sunset, a full moon rises on the opposite horizon. This is what we have been waiting for—the spectacle of reflected light. The glazed snow glitters and shines. The world, in just that moment, that splendid moment, is renewed.

Change. Landscapes change in just this way and through hundreds of other events, some cataclysmic and some in ways just like this, changing for a few short hours or days, and others for keeps, or seemingly so. Some changes are good from a certain perspective, maybe from yours. Others are not as good. We live for some, while dreading, occasionally fearing, others. The right mood, the perfect time of day, can make a rain shower into a miracle, while too much rain and too little preparation can bring disaster.

It is never just the weather, of course. It is what the weather does with the plants and animals, the microbes, the soil, the underlying rock. Count the contingencies: winter or spring, summer or fall. A forest of trees and understory. Or fields after the harvest. Wet, heavy snow or flakes so delicate they nearly refuse to fall at all. Temperature, relative humidity, wind speed, barometric pressure. Sand, soil, or stone. Cliffsides and gentle slopes. The list of contingencies goes on. It is customary to think of landscapes as reliable, rooted in solid ground and (while moody perhaps) unchanging in ways that reassure. Absent an earthquake or some other catastrophe, our dooryards feel permanent enough. But landscapes never are this, although some will change more rapidly than others. In any case, we tend to take landscapes for granted, rarely devoting much time to make a list of each contingency, each this-depends-on-that. These are the elements of change. They, not permanence, make our dooryards what they are.

What of climatic changes, then? How will the changes in climate transform your dooryard and mine? How deep, how lasting will the changes be? Will each change be but tiny, each difference adding to those before? Answers to these queries can be predicted in some gross and abstract ways; but together with other instances of it-depends-on-that, we can only watch, wait, and see.

As we watch and wait, it is reasonable to ponder: what is the nature of change itself? Seasons change and landscapes change, but are these changes real? Our planet has warmed before and has cooled down again. Are these actual changes? Or are they something different? Is change real, or are changes just cycles, like seasons—part of something larger than any single change, something unchanging in itself? This is an old question, one of the oldest in philosophy. Go back more than two millennia and you will find two philosophers staking claims to each side of it. Heraclitus and Parmenides (who are known as pre-Socratic philosophers) defined the terms of a debate that Parmenides, for the most part, won.

Heraclitus, for his part, held that all was flux, that change was the only constant. You can only step into the same river once, he was quoted as saying, both metaphorically and not. Step into it a second time and it has changed. It is not the same river. Parmenides demurred: change, he said, is an illusion. And while that makes little sense intuitively (change certainly seems real enough when it happens), Socrates and his acolyte Plato came down on the side of Parmenides. Change is illusory, is always underlain by the unchanging, the permanent, the foundation. The universe is not a river but a sturdy house. Philosophy and its daughter, modern science, agree on this point. Change, at some level, is simply an expression of some underlying law, some unyielding and permanent process.

Phenology seems a case in point in Parmenides’s favor. The seasons bring change. Trees bud, buds become leaves. Branches once barren are now filled with growth. Birds build nests, lay eggs, raise chicks. Chicks fledge and fly away. As summer becomes autumn, the leaves turn color and fall. Where it is cold enough, the rains become snow. It all repeats anew the following year. Change, and yet unchanging.

Does this mean that climatic changes, the manifold consequences of climate change, have no reality? Here is an answer: one thing that paleontology shows is that the chance that any given species will go extinct is 100 percent. Yes, someday polar bears will become extinct—along with every other species. It is simply a matter of time. This is the unchanging thing, but it is of little consolation to the polar bear, or to any other species member who departs with the rest of its clan because natural selection has zeroed it out in the Anthropocene. In this sense, Heraclitus was right: the change we experience is real and ever present, even if it is the consequence of universal laws that are themselves constant through time. Rivers change from moment to moment. They swell from the spring melt, flood whole towns, and sometimes take lives.

The reality of change is a matter of perspective, of where one stands. Figure 5.1 compares rates of change of the basic features of any given dooryard: bedrocks, surfaces, ground and surface water, soils, plants, animals, weather. It simplifies matters quite a bit, as do all such graphs. In this one, change happens more rapidly the higher one goes on the vertical axis, less so the deeper one plows. Our best assurance that change is real is that we can measure it and compare one change with another. This chapter provides an overview of these components of the landscape and provides suggestions about ways that you can create a baseline for noting and measuring change over the coming years and decades.

Bedrock. Bedrock changes, but it does not change quickly. (If you happen to live in the path of lava flow from an active volcano, as in Hawaii, take the previous sentence as an obvious overgeneralization.) Geologists have classified bedrocks by periods, which are measurable in time. Beneath my dooryard in Maine, the bedrock was Ordovician in age, meaning that it has been around (although not at the surface) for close to 500 million years. The bedrock underlying the cinders at my Arizona dooryard is Permian—perhaps 275 million years old. You can discover the age of the bedrock at the foundation of your dooryard and the period in which it falls, if you wish, by searching the Internet (enter “bedrock,” “geology,” and the name of your town in the search engine) or by purchasing a map from your state geological survey. Geological maps are not difficult to read, and are invariably colorful. Because bedrock is the most permanent aspect of your dooryard, it is perhaps the least interesting part of your baseline. But it is interesting to know all the same. In many places, fossils from past geological times are not far underfoot.

The shape of the land changes more quickly. In northern states across the United States, the landscape has been shaped by ice that retreated in some places a mere ten thousand years before the present. Glaciated regions are covered with drumlins, eskers, kettle lakes and ponds, moraines of various kinds, and other products of the most recent ice age. Learning the meanings of these terms and identifying the features that correspond to them enriches your understanding of the surrounding landscape. Residents of eastern Washington state may know that parts of the landscape there, known as the channeled scablands, formed in an enormous flood, with a headwall perhaps five hundred feet high, that occurred when an ice dam breached, emptying a lake in a very short time. Knowledgeable coastal Californians look at the mountains around their dooryards and associate them with the earthquakes they experience from time to time. Other coastal dwellers, such as those who live near the beaches in North Carolina and South Carolina, have seen islands form and disappear as a result of hurricanes. Who can forget the devastation that occurred in New Orleans in the wake of Hurricane Katrina?

The study of the surface of the earth is called, not surprisingly, surficial geology, and the branch of geology that studies those processes that make the surface what it is, is called geomorphology. Depending on what place you call your dooryard, there is a chance that it will go through some geomorphological change over the decades to come. Increased precipitation (a generalized expectation in a warming climate) may lead to erosion (although it might just as likely provide denser ground cover, preventing erosion).

Just as there are geological maps of bedrock, so, too, there are maps of surficial geology. These, too, are colorful but perhaps not as intuitive to read. If you belong to a garden club, or an environmental organization with local chapters, it is well worth the cost of a small stipend to engage a local geologist for a field trip. Although geomorphology today is largely quantitative in practice, an older tradition told stories about landscapes—stories rooted in time, structure, and process. Geomorphologists, even those of the quantitative sort, have fascinating stories to tell. Rivers, beaches, lakes, hillsides, shorelines, and other features of the earth’s surface tend to be, in a geomorphologist’s mind, a sort of motion picture in which the present is a momentary freeze frame. There are few places in the United States that have not changed in profound ways over the past few thousand years.

Soil, the varied top layer of “solid” ground, changes even more quickly than does the surficial geology. Gardeners commonly think of soil as the product of their own toil as they turn it, adding various amendments and compost, working to achieve a proper acidity for the plants they wish to grow and harvest. But soils will change without the helping hand of a gardener in a succession from purely physical sediments to a biota in their own right, teaming with microbes, animal species, and plants. In time, the primary succession from sediments to soil will be disturbed by fire, by the introduction of new species (with or without an anthropogenic cause), and by climatic change. It is the last of these that interests us. Climatic changes may bring about higher soil temperatures at new times of the year, causing a secondary succession in the soil, that is, a change from one kind of soil to another, with a revised set of microbes, plants, and animals.

Liquid water in bedrock and on the surface of the land is highly variable. Vernal pools, some as large as ponds or lakes, appear in springtime, as their name implies, and disappear for the rest of the year, along with much of the biota they briefly support. Ground water moves, but large aquifers may impound water for millennia. Lakes are ephemeral on a geological timescale and may change more quickly during droughts and periods of heavy precipitation. Terry Tempest Williams’s Refuge, a natural history of the Great Salt Lake region in counterpoint to the story of her mother’s cancer, uses changes in the level and shoreline of the lake (which is itself merely a remnant of the far larger pluvial Lake Bonneville) as a marker of the passing of time.

Rooted in the soil, plants change with rapidity, and animals even more so. Air, on a windy day, scarcely rests for a second, but that is the subject of a subsequent chapter. We can think of plants and animals, en masse, using two concepts in ecology: life zones and succession.

Life zones. Almost anyone with a respectable interest in biology has made a pilgrimage to the Galapagos Islands, venturing forth in their imaginations if not in actual fact. One half imagines that, while gathering together for one reason or another, virtual pilgrims, together with those who have managed to make the actual trek, raise their glasses and toast: next year in the Galapagos. This is a fine sentiment, and one that I share—to make a journey to the very place where, according to the myth that he promulgated in his autobiography, Charles Darwin got the idea for natural selection by observing variations among the finches that populate these islands. Even those who know that this was not the case, that the road to a theory of evolution was more complex, that Darwin was oblivious to the significance of the finches until long after he returned to England, still celebrate the Galapagos. There is value to myth, and I respect it. Equally important, the Galapagos are a cluster of contingent landscapes that drive evolution. By the time he wrote his autobiography, this notion about the significance of the Galapagos had fully crystalized in Darwin’s mind.

It seems a shame, then, that Little Spring in Arizona is not so highly regarded. I have successfully made the latter pilgrimage once, and I attempted it more than that. Little Spring is to ecology what the Galapagos are to evolutionary biology; at least I like to think that this is so. On my first pilgrimage there, I missed it entirely. But I was thoroughly entranced by the journey, via a National Forest Service fire road, through Hart Prairie at the western base of the San Francisco Peaks north of Flagstaff, Arizona. The aspens were golden in autumn and stark against the blue sky. The next time, a full decade later, I was more successful just because I did something I wouldn’t do the first time around. I asked a forester for directions.

“Go up this way,” he said, pointing down a dirt road carpeted in fallen aspen leaves. “You will come to an opening. When you get there you’ll see a two-track. Follow that up into a stand of Douglas fir. You’ll find a plaque.”

I didn’t quite know what a two-track was, but I could guess. As I reached the open meadow, I found a promising double trail, tire tracks: a two-track. I followed it into the stand of Douglas fir and found the plaque without much trouble. I laughed when I read it. The text on the plaque was more of a tribute to the people who placed it there than to the historical circumstance it commemorated. Two dates are given along with an abundance of text, none of which have anything to do with the significance of the site. No matter. I had found it. This was the site of C. Hart Merriam’s base camp in the summer of 1889, the place where the life zone concept (and its progeny, the biome) was born. This, when he and his assistants were not out collecting, was Merriam’s temporary dooryard. How much had changed since that summer more than a century before, I could not say. I felt certain that the stand of aspens on the far side of the meadow weren’t there and would not have presented the golden spectacle of autumn leaves that I was witness to. But other aspects might have been similar—not the same trees, but the same species. The camp was in a stand of Douglas fir in 1889, according to Merriam’s description, and they were in a stand of firs when I saw them.

In 1889, the U.S. Department of Agriculture dipped into discretionary funds and found $600 to support an expedition designed by Merriam to survey the biological wealth of the American West. For their money, Department of Agriculture got one of the great bargains in the history of science. It was too little money to do more than make a drop in the bucket with respect to mapping the biological resources of the West, much less the United States. But Merriam emerged from the summer expedition with something else—a comprehensive theory of the distribution of species that we know today as the life zones theory.

With his wife and with assistance from Vernon Bailey, Leonhard Stejneger, and locals hired from the incipient town of Flagstaff, Merriam spent the summer traversing the San Francisco Peaks and the surrounding Colorado Plateau, from deep inside the Grand Canyon across the plateau to the top of Mount Humphreys, and into the Painted Desert to the east. He applied methods that the great German naturalist, Alexander von Humboldt, developed in South America; Merriam recorded measurements of temperature and barometric pressure, slope, and temperature and noted the relationships between these and the organisms he found. From those relationships, over the course of the summer of 1889, Merriam generalized seven distinct life zones.

In his conception of the life zone, Merriam had done what pioneers in science do: he had devised a first approximation of order from seeming chaos—that is, he originated a very good idea. It was much too orderly, but it was a good idea, and it provides a road map to climatic change. As a rule, as mean global temperature increases, zones will move northward (if north of the equator) and southward (if south of the equator). And they will move upslope in either case. Species that can move with their zones will survive; those that cannot will become extinct.

The U.S. Department of Agriculture adopted Merriam’s system of zoning to develop their map of plant hardiness zones for North America, which gardeners know well, just as they know that full sun, partial shade, and full shade make a difference in what to plant. A glance at the department’s map shows what’s at stake: the boundaries of each zone are sinuous and convoluted. As climates warm, these twists will not simply move north. They will change according to local conditions, just as they were initially inscribed on maps with reference to local conditions. Assuming that change is kept somewhat in check by more enlightened policy making than is evident at the time I write this, gardeners (and farmers) will experience only the mild inconvenience of having to choose different seeds, different varieties, forgoing some vegetables in exchange for adopting new plantings.

Wild plants will be at more of a disadvantage. As wild plants reproduce, they do so in what seems to many of us as an inefficient process. Saguaro cactuses may each produce as many as a hundred thousand seeds, only one of which may survive into adulthood. The survivors, in their early stages, are known to foresters and botanists as recruits. Climatic change will reconfigure the conditions in which recruits survive. Generally this will be upslope or northward (in North America), all else being equal. But slopes are never infinite; they top out. And landscapes are fragmented. Plants, in the process of migrating to compensate for climatic change, run up against four-lane interstates, farms, suburbs, and cities. When they do, they run out of luck.

The add-in is contingency, the state of “it depends.” Landscapes are contingent; they are contingent on a great many factors. The simple idea of changes in altitude in Merriam’s very good idea is expressed in nature in slopes, which twist and turn every which way. Think of a ravine or deep valley running from east to west. The north-facing slope will be shaded in parts for much of the day, changing the application of the simple rule. Shade has an effect not just on photosynthesis but also on soil temperature, in varying degrees. A rising annual mean temperature may change the soil temperature but not the exposure of plants to sunlight.

Moreover, the migration of plants usually occurs over centuries, not decades (although more rapid changes do occur, and I will discuss this later in the chapter). There are already initiatives afoot to help nature through managed migrations, but the task is daunting and is currently unpopular with some climate change activists.

Succession. Ecologists (and others) use the term “succession” to refer to a series of changes in the makeups of soils, plants, and animals in the landscape. Some of these changes are regular, and some are contingent. Both Parmenides and Heraclitus would draw interesting conclusions from a study of the successions caused by beavers and the transformations they bring to the landscapes of North America, now and in the past. Heraclitus would point to changes, day to day and year to year, that beavers initiate in the landscape. Parmenides would counter with cycles, and the longer-term unchanging nature of things. Both might ponder the introduction of trappers, which decimated populations of beavers for a time and brought the cycles and the short-term changes to an end. You may have encountered this story as a child, but it’s worthwhile repicturing the full process, because it is the essence of cyclical landscape succession.

Picture in your mind a forest in a modest valley, wide and not too deep. There may be some openings in the tree canopy, but this is clearly a forest, possibly made up of maples, oaks, and birch. Trees and the wildlife they support dominate the landscape. In the midst of the forest, a stream bubbles and flows as it makes its way downslope. There may be fish—minnows or larger fish—in the stream. There are crawdads. Moss grows on rocks in the stream. Were you to step in it, it might well be cold.

One day, a beaver discovers the forest, makes a note of the stream, and surveys the abundant resources. The next day, she returns with other beavers, who begin to gnaw through younger trees with their teeth and then drag the trees into place across the stream. Before long, they have created the framework for a dam across the stream. They begin to infill the frameworks with smaller branches and mud. As the stream begins to back up behind the newly engineered dam, the beavers construct lodges in the area that will soon enough become flooded; placing the openings to the lodge below what will become the waterline. Soon enough, the lodges are complete and water sufficient to create a pond has impounded behind the dam.

Out in the pond, some trees that were too large for cutting remain standing; in time, they will die, but in the meantime they make ideal aeries for predatory birds, hawks and eagles, who feast as a result of the revised ecology. Where there were woodland species with a riparian strip (a grouping of plants and animals that only live close to water, in this case, the stream), there are now a host of new aquatic plants, invertebrates, and vertebrates. Insects provide meals for dozens of species of birds that would have bypassed this place before the beavers came.

It is a pocket paradise, but with each passing year, spring floods make work for the beavers, who must maintain the dam in good working order. With each spring flood comes sediment, which falls to the floor of the pond in the low-energy environment. Each year, this raises the bottom of the pond. The dam must be built higher, and wider perhaps, to do the same work that the original dam did. The lodges, too, must be adjusted.

Then, one spring, a fifty- or hundred-year flood washes out the dam. Some of the beavers do what they can to restore it, but others scout nearby woodlands and find a suitable spot for creating a new beaver pond. Before long, the old pond is abandoned. The dam, in disrepair, ceases to hold back the flow of the stream. The floor of the pond, now exposed, changes from mud to soil. Seeds, some of them carried by animals and others wind-borne, settle into the soil and germinate. Before long, the pond floor has become a meadow, filled with flowers and grasses in spring and summer. The meadow is a popular browse, where deer sample the plants. With such abundance, the deer can afford to pass over the woodier species of plants in favor of tasty shoots. A pack of wolves settles nearby, enjoying the deer. All of the animals make use of the stream, which has reestablished itself in a somewhat different course.

Small pockets in the pond floor still fill with water in springtime and host frogs into the warmth of summer. The sky is busy with birds, some nesting there, others in the old forest that ringed the beaver pond. In time, the woody plants that the deer pass over become saplings, and the saplings become trees. The trees pass through a succession of their own until finally this is once again woodland, with a few openings in the canopy but otherwise, a forest. And one day a beaver visits. Parmenides is pleased. Nothing changes. Heraclitus shakes his head. Everything has changed.

The cycles of succession that beavers engineer are dramatic, but every landscape is the consequence of succession, sometimes in progress (where a disturbance has occurred) but often in a condition that ecologists loosely call climax. Whether climax landscapes will undergo a new process of succession in response to climate change, and how those successions will unfold in case they do, is an open question—and one of the reasons that phenology as citizen science is gaining standing.

History and archaeology. Fires and beavers are not alone in bringing change to the landscape. Humans are engineers, too, and have been transforming the North American landscape for around fourteen thousand years.

When I lived in Maine there were occasions when I took my household of cats—Phoebe, Grebe, Oscar, Charlie, and Cloud—for short hikes through the woodland behind my home. They seemed to enjoy this, even though the activity required frequent coaxing on my part. Cats have an innate sense that, really, this is just too far from home. They would protest. I would encourage. A few words were enough to keep them moving forward. Invariably, we would come across stone walls in the woods, monuments to industry in an otherwise natural setting. The cats intuitively treated these as clear barriers to further progress.

At first, the walls made no sense to me. But stone walls are part of the mythology of Maine woodlands, and in no time I knew about their provenance. At each wall I encountered, I was witness to four processes. The first was glaciation and the retreat of ice from Maine around ten thousand years ago. The ice left behind a rubble field extending for tens of thousands of acres. In an older tradition, geologists referred to the rubble as “drift.” Later, it became known as moraine. Next, forest succession changed the landscape into woodland. Then, in the eighteenth and nineteenth centuries, farmers cut the forests here, partly to clear the land for pasturage and partly to provide wood for construction and for heat through the long winter months. It was because of their interest in pasturage that farmers moved the morainal rocks, using stone sleds in the winter months and constructing a variety of stone structures usually no more than three feet tall.

Finally, agriculture moved west. Pastures, no longer needed, were left fallow. Forest succession renewed. New England was transformed once again into a vast secondary forest—with odd stone walls separating patches of woodland with little difference between the patches.

On the other side of the continent, in the desert landscapes of California, one may encounter, while hiking, piles of stone with a quite different explanation. These piles are ancient fish traps, created by Native Americans thousands of years ago to impound fish in the vast, shallow lakes that formed here during the last ice age and that disappeared completely only a few hundred years ago. (Some such lakes, such as Lake Owens, persisted into historical time, only to disappear into the pipes and aqueducts that feed the farms and urban environments of California.) Coastal areas in many parts of the United States have archaeological remains of technologies developed by Native Americans to impound fish, but to find such devices in the clear absence of water in the present day is a little unsettling.

Local history and archaeology are useful resources for developing an overall picture in your mind of your dooryard’s past. While the differences between history and archaeology aren’t important for holding that picture in your mind, they are quite different for the people who practice them academically and professionally. Historians, to an overwhelming extent, ground their work in textual evidence—letters, notebooks, journals and diaries, newspapers, court records, and books. Anything that is written and preserved is grist for the historian’s mill. Archaeologists, in contrast, look to physical evidence as the basis for making claims about the past. Tools, middens (trash piles), and other kinds of physical evidence are the raw materials of archaeological knowledge. In some cases, as in projects involving historic preservation, historians and archaeologists set aside their differences and collaborate toward common ends. But much of the time, they work in the same places using different intellectual tools. It is often the work of some third party—a museum curator, a ranger, a naturalist—that brings their work together.

One tool that archaeologists use would leave historians scratching their heads. That tool is pollen. There is a whole subdiscipline of science devoted to the study and classification of pollens—palynology—and a sub-subdiscipline that focuses on ancient pollens. The latter is called paleopalynology. Paleopalynologists collect pollens from the layers in which they are preserved at the bottom of a lake or pond and, from them, develop a picture of the set of plants that grew and in what abundance at some time in the past. Archaeologists tend to use paleopalynology as a tool for correlating sites (that is, showing the relation in time between two or more sites) and for painting a picture of the contemporary ecological landscape for a site. But paleopalynologists are interesting in their own right. If you ever have an opportunity to talk to one, take advantage of it. The chances are very good that a paleopalynologist can reconstruct, in considerable detail, a vision of your dooryard or someplace nearby, as it was some time in the past. Was it once a meadow, or woodland? A paleopalynologist can provide the answer.

Large parts of the American landscape went through a fairly cataclysmic transformation in the few centuries following European contact. Enterprising individuals, making use of their own labor or the hard work of free men and slaves alike moved rivers, shaved mountains, replaced whole ecosystems, drained lakes and wetlands, and created roadways to move goods and resources from one end of the continent to another. The local impacts of the centuries of industry interest us here, as do the changes wrought by Native Americans before European contact. Currently, the resources available in print for the lay reader are somewhat patchy, but to get an idea of the extent of change, the exemplar is William Cronon’s Changes in the Land, an overview of the transformation of the New England countryside.

Nothing comforts the soul so much as knowing where to begin. For the complete phenologist, the point of departure is best marked by establishing a baseline.

The next few pages, like the bulk of this chapter, are not about phenology, per se, but they are helpful both for making phenological observations and for appreciating their meaning, not simply over time but from month to month. The idea is to take Heraclitus and Parmenides out in the field with you to create an inventory of the changing and the unchanging, the precarious and the stable. Heraclitus would have you see that all of it is precarious, while Parmenides would have you focus on the stable, warning that you should not miss the forest for the trees. (Yes, he will talk in clichés just like that. He invented some of them.) As field assistants, they are a mixed bag. Neither is at all useful for carrying gear or even lunch, and they both tend to be biased and overbearing. But, in general, they will aid your observations and notes more than they will detract.

While it is not necessary to create a baseline in order to record phenological change over time, or to be mindful of the present time, it is a useful early step to take, and not just for recording change. It is a way to, as progressive agronomist Wes Jackson has put it, become native to this place, if one has not already established that valuable sense of rootedness. In this chapter, we look at the geological history of our dooryards, the recent geographical circumstances that create these places as they are today, and the life zones in which they are placed—as well as the changes in the physical, biotic, and human landscapes that may come about over future decades. We will then look at three aspects of creating a baseline: mapping your greater dooryard; establishing one or more transects that connect your dooryard to the greater landscape; and using repeat photograph, or rephotography, to record change visually, establishing the archaeological and historical roots of the place where you live.

It is a good idea to establish a baseline now. In words Heraclitus might have used, it’s time to step into the river once and take note of it before stepping into the river again, and again, in order to measure change and to learn from this unfolding experiment. These dooryards, real and figurative, yours and mine, are set within larger landscapes about which many things are known. Poets and essayists may have written about them—think of Thoreau, Muir, and Abbey—and scientists have certainly measured and described them, collected them and shrunk them down to the size of lists and maps. But the devil, it is said, is in the details, and the details are the essence of this book.

Repeat photography. Beginning around the turn of the last century, farms and rangeland in the American Southwest began to experience a process that locals called “arroyo cutting” (arroyo, which sounds pleasing, is Spanish for ditch). Streams and washes would suddenly erode and deepen, taking vast acreages of arable soil with them. Was this a consequence of grazing, or of overgrazing? Was something else at work? Geologists, such as Kirk Bryan, from Yale University, attempted to answer these questions, but the variables were complex. The climate of the Southwest has changed over the past 150 years, only partly due to anthropogenic factors, and this must be taken into account along with land use. With no clear solution in sight, a historian at the University of Arizona named James Rodney Hastings began a research project to find an answer. Hastings found photographs from the 1870s, 1880s, and so on. With some ingenuity, he was able to take photographs at the same positions and with the same angle of view as those he had found, giving him a comparison photograph. Most of Hastings’s “repeat photographs,” published with coauthor Raymond M. Turner in The Changing Mile: An Ecological Study of Vegetation Change with Time in the Lower Mile of an Arid and Semiarid Region, are so accurately matched that one can scan the earlier and later photos and show them in sequence in a PowerPoint presentation to dramatic effect.

As a way of showing dramatic change, rephotography is better suited to the open landscapes of the American West than to other parts of the United States, but repeat photographs can be helpful for noting change anywhere. To create a baseline, simply create a marker using a permanent stake or, better, a six-inch-square bit of concrete with the center clearly marked. Place a camera with a known focal length on a tripod over the marker, using an improvised plumb bob (a nut or another heavy object tied to one end of a piece of string) to center the camera over the marker. Be sure to make note of the height of the camera above the ground or marker. With a compass, take photographs in sufficient number to complete a panorama, making notes of the compass angles for each shot. Then repeat this process on a regular basis, as often as you wish, but at least once a month for the first year. Thereafter, repeat again on the same days of each year.

If you already have photographs of your dooryard, you can try to match up the camera position, focal length, and date in order to establish a baseline earlier than the present. This may require some experimentation but will deepen your repeat photographic record. Picture Post, part of the Digital Earth Watch network, is an opportunity for citizen scientists to make and submit repeat photographs.

A map or aerial photograph. A detailed, scalable map of your immediate environs is a helpful thing. Such a map can be drawn as a sketch map, to scale or not. But aerial photographic views, made in two or more seasons, are an improvement and are, if you are so inclined, quite a bit of fun to make. The obvious way to create an aerial view of your dooryard is to use a drone; the technology is currently developed to make this a relatively simple option, albeit an expensive one if you must purchase a drone with camera. But rentals are possible. For instance, as of 2015, Photojojo, in San Francisco, was renting a drone with digital camera for under $100. The downside, for those who do not live close to the city, is that you must take a lesson in flying the device before you can rent it.

A lower-tech option, and one that may be a bit more fun, is kite aerial photography, a hobby that has developed with the Internet. The guru of this type of photography is Charles Benton, professor of architecture and the University of California at Berkeley. Benton has been taking kite aerial photographs for more than a decade (at this writing) and posting them to his website, along with many webpages devoted to the equipment and techniques required to make quality images of this sort. There are also web retailers that specialize in a full range of equipment. Images of your dooryard, made at different times of year using kite aerial photography, can be repeated (although exact repeats are difficult) for comparison over time.

A phenological trail. The most useful task you can undertake in advance of keeping phenological records is to establish a phenological trail—a line through the landscape that extends from your dooryard, which is a point on the line. It need not be a straight line. Zigzags are fine if they pass through varied landscapes and biomes. The best way to make sure of that variation is to change altitude, even if this involves only a few feet. The close-in part of your phenological trail should be a distance that you can traverse every day. Farther out, you might want to cover ground once or twice a week or, farther still, at least once a month. As you establish your phenological trail, get to know all of the plants along the route. Ignore the distinction between naturally occurring or native plants, on the one hand, and garden or farm plants, on the other. All are grist for the phenological mill. The camera is, once again, your friend. Digital photos cost nothing, and you can, if you wish, photograph every foot of your phenological trail.

Depending on how much of the foregoing work you take on, you will have made a substantial investment in knowing your dooryard. Photos, maps, and learning are an outlay of time and effort, even if they are inexpensive in dollars. What becomes of that investment if you move, say, in five years? Or in twenty? If you have found your phenological work worthwhile, you will no doubt begin again in your new home. Perhaps you can persuade a neighbor, or the new occupant of your former dooryard, to continue your records and to share them with you. And you can contribute them to the USA-NPN. The simplest answer is to say that, by developing a baseline and phenological records, you have indeed become native to this place. If you move, any return, on any interval, will be a homecoming of sorts. And should you remain, you’ll be witness to all changes, great and small, the fortunate and the unfortunate.