As did many Americans, I first grew alarmed about global warming in 1989, when Bill McKibben published The End of Nature. I already knew that warming, or climate change, was a problem. But McKibben, along with the conversations that his book spawned, provided a framework for thinking more deeply about this emerging environmental threat. My concerns deepened when, in 1995, I began to teach a course titled History of Environmentalism at the University of California, San Diego, with readings from Henry David Thoreau and Aldo Leopold. It was while preparing the lectures for that course that I first encountered the strange, not-yet-quite-really-a-science, phenology, the observation and study of biological cycles having cues in climates and seasons. Within a year, I began to assign the writing of a phenological journal as part of the course. Students chose a patch of nature, identified the plants growing there and any animals that passed through, described them (and any changes, although there is sometimes little change during a Southern California academic term), and at the same time reflected on course readings and discussions.
My interest in phenology and in seasonality broadened when I began to explore a landscape new to me, the Sonoran Desert, where the plants and animals seemed to wear their phenologies on their sleeves and seasons have peculiarities I’d not before encountered, such as the “monsoonal” rains, thunderstorms, and dust storms of Sonoran summer. Guided by the books of Gary Paul Nabhan, Ann Zwinger, and Ed Abbey, I grew to love the region and to enjoy its intersecting phenophases and phenological cues.
Since that time, phenology has shed some of its obscurity, almost entirely due to its relevance for tracking and confirming the consequences of anthropogenic climate change for Earth’s biota. Today, a host of websites is devoted to aspects of phenology. Almost all of them begin with an introductory paragraph designed to answer the question “what is phenology?” If the present book does nothing else, I hope that it answers that question with sufficient clarity and verve that “phenology” becomes as common in the vocabulary of environmentalists and amateur naturalists as “paleontology,” “hydrology,” or any of dozens of terms that designate areas of scientific observation, inquiry, and expertise.
As a way of opening new doors to an understanding of climate change, including changes that are unfolding even as you read this, Ground Truth turns to phenology and to related areas, such as seasonality (which deals with physical cycles over the course of a year, as opposed to phenology, which is about annual biological cycles). Both of these are our present reality. This book is not designed to convince you or anyone else that climate change is occurring or that it is caused by human activity. Of course it is occurring. Of course it is caused by human activity. There are presently hundreds of books devoted entirely to showing this. I won’t add to that glut. I might as well exhaust our energies proving that day comes after night.
This book is not a textbook. Neither is it a comprehensive manual for pursuing phenology as a citizen scientist, although I fervently hope that citizen phenologists find in these pages a welcome companion. Rather, it is about three things: climate change, seasons, and phenology. I hope that anyone with interests in birds, rocks, trees, wind, butterflies, deer, beetles, blue skies, flowers, and the rest of the natural world will find something of interest here.
Part 1 of the book introduces phenology as a way of coming to terms with climate change; it prepares you to make phenological observations and keep records. In the first chapter, you will learn about the value of phenological observations for paying attention to your own place in history—and in nature. Chapter 2 shows that anthropocentric—human-caused—climate change is a developing phenomenon, and you will learn about connections between seasons and climate change. The third chapter is a brief history of phenology. In the fourth, I talk about observing, record keeping, and the uses to which phenological observations can be put. The fifth chapter examines the nature of change itself and provides some quick guidelines as to how you might measure the changes in your local landscape that will unfold in years to come.
The five chapters that make up part 2 look to a set of essential details for following the phenologies of plants, invertebrates and amphibians, birds, and mammals. There is also a chapter on weather, which is not, strictly speaking, a subject of phenological study but is closely related to it.
These chapters are no more than introductions to their several subjects. Those who already watch birds, know their plants, or keep a weather station will find them rather too elementary. My goal is to whet appetites and to offer some guidance, not to provide a definitive overview. Neither have I made an attempt to organize each of these chapters following a unified plan, wherein the contents of one chapter correspond to the next. Instead, I have let the subject matter shape the organization of each chapter.
I discuss the ranges of plants and animals, sometimes by naming states where they are present; but in cases where they range over many states, I will mention the states from which they are absent or mostly absent. I also sometimes mention regions, such as the northern Great Plains or the Mississippi River Valley. More precise range maps can be found in guides to wildlife and plants, and these are listed in the bibliographic essay. It makes no sense to duplicate these here.
In discussions that contain phenological dating, for instance, “late fall to early winter,” or “November to early February,” the range of dates often reflects the extent of the geographical range, where “late fall” events tend to occur in the north and “early winter” events farther south. In the same way, “late winter to early spring” events range from south to north.
Part 3 consists of a single chapter, in which I raise larger issues with respect to anthropogenic climate change.
I present two different conceptions about phenological observation in this book and have taken pains to keep them separate without opposing either of them to the other. For centuries, even before there was a word to describe what they were doing, people from all stations of life have tracked seasonal cycles in plants and animals and have made entries in notebooks about what they’ve observed. I discuss some of them in chapter 3. For the most part, these were amateurs, with an interest in describing local phenologies, a curiosity entirely in keeping with their zeal for discovering local plants and animals and even fossils; describing them; thinking of their home as part of a natural tapestry or a symphony. I have attempted to prepare the groundwork for their present-day successors, the people who wish to catalog and to know what I call (after the practice in parts of New England) their dooryards. When I speak of your dooryard, by the way, I’m making a technical point about the difference between that place and the commons, another New England land-use designator. The commons is shared, whereas your dooryard is in some ways yours and yours alone, in your thoughts if not in property law.
In addition to individual interest, there is another reason to keep records of phenological events. The appearance of flowers and the “hatching” of insects provide valuable data by which scientists can track climatic changes as well as build predictive models for understanding how nature is currently changing. These scientists are very much in the business of developing models with which they can understand and predict ecological change. In more than one place, I put a diminished emphasis on using phenological observations and analysis as a way of making predictions, whether of future climatic changes or more specifically about ecological or environmental changes. This is not because I do not recognize the value of predictions, or that of the models being developed in order to make predictions. These will grow more sophisticated over time and will play important roles in mitigating environmental damage from climate change, when this is possible—damage that will include the extinctions of species. My lack of emphasis here regarding the predictive value of phenological observations reflects a choice of focus: I want to highlight observation while bracketing the purposes to which observations might be put—the knowledge on which they may bear. This is more than what scientists once called Baconianism and still sometimes call “mere description.” But it is, in fact, at least that. Accurate observations, carefully recorded and (in some cases) reported, have a beauty and a rigor unto themselves. More than that, the overall drift in this book is toward making up one’s own mind about the relationship between anthropogenic climate change and the nature through which one passes every day.
It may bemuse some that this book was written by a historian of science rather than by a working scientist. In pursuing these topics—climate change and phenology—I follow on a trail broken earlier by several of my colleagues, who have seized on climate change, the sciences, and the social institutions that surround a concern for the earth and its environment, with an energy and deep concern that I hope also inspires others in years to come, as they have inspired me.