"Many of the findings in the book . . . are classics of ecology. . . . A rare and delightful insight into timely science."—Jane Lubchenco, Nature
"Estes's refreshing narrative deftly weaves rigorous science with personal reflection to create an absorbing and introspective read that is equal parts memoir, ecological textbook, and motivational guidebook for young ecologists."—Science To newly minted biologist James Estes, the sea otters he was studying in the leafy kelp forests off the coast of Alaska appeared to have an unbalanced relationship with their greater environment. Gorging themselves on the sea urchins that grazed among the kelp, these small charismatic mammals seemed to give little back in return. But as Estes dug deeper, he unearthed a far more complex relationship between the otter and its underwater environment, discovering that otters play a critical role in driving positive ecosystem dynamics. While teasing out the connective threads, he began to question our assumptions about ecological relationships. These questions would ultimately inspire a lifelong quest to better understand the surprising complexity of our natural world and the unexpected ways we discover it. Serendipity tells the story of James Estes’s life as a naturalist and the concepts that have driven his interest in researching the ecological role of top-level predators. Using the relationships between sea otters, kelp, and sea urchins as a touchstone, Estes retraces his investigations of numerous other species, ecosystems, and ecological processes in an attempt to discover why ecologists can learn so many details about the systems in which they work and yet understand so little about the broader processes that influence these systems. Part memoir, part natural history, and deeply inquisitive, Serendipity will entertain and inform readers as it raises thoughtful questions about our relationship with the natural world.
About the Author
James A. Estes is Professor of Ecology and Evolutionary Biology at University of California, Santa Cruz. He was coeditor of Trophic Cascades: Predators, Prey, and the Changing Dynamics of Nature and of The Community Ecology of Sea Otters, and senior editor of Whales, Whaling, and Ocean Ecosystems (UC Press). He is a recently elected member of the National Academy of Sciences.
Read an Excerpt
An Ecologist's Quest to Understand Nature
By James A. Estes
UNIVERSITY OF CALIFORNIA PRESSCopyright © 2016 The Regents of the University of California
All rights reserved.
In the Beginning
IT WAS MAY 1970. I had finished my master's degree the previous spring, but the Vietnam War was raging and the draft board was hot on my heels. Military service seemed imminent, and my thoughts were mostly on how to do this as quickly and safely as possible. I had been weighing two choices: the draft and a two-year stint in the army (short but dangerous, and with little imagined value) versus officer training and four years in the navy (longer but safer, and more interesting). Four years seemed like a long time, so I opted to take my chances with the draft.
I was single, fit, and in excellent health — seemingly an ideal prospect for military service. After receiving my notice to report for the preinduction physical, I showed up at the Spokane induction center fully expecting this to be the first step toward boot camp and a stint in the army. Draft dodging was in vogue in those days, and many of my fellow preinductees had letters from their physicians, psychiatrists, preachers, and the like, explaining why they were physically or psychologically unfit to serve. The induction staff had seen it all before and regarded every one of these would-be draft dodgers with obvious disdain. There were hundreds of us, assembled alphabetically in lines and ordered to strip for what amounted to little more than confirmation that major body parts were intact. Everyone passed. This was followed by intelligence and mental-stability tests. To my amazement, a few of the preinductees actually managed to fail this second part of the exam. But the saying in those days was "If you have a pulse, you're fit to serve," and I had little hope of not making it through the perfunctory battery of examinations.
The last step of the preinduction physical was a short interview with a military physician. It was at this point that the paper waving and ululating reached their crescendos. My examining physician, a tough-looking marine named Sanchez, patiently listened to each man's story, looked over his paperwork, and then stamped him "fit to serve." When my turn came, Dr. Sanchez seemed surprised by the lack of excuses and said as much. At the end of the interview, he asked if I was sure there wasn't something physically or mentally wrong with me that should be noted in the paperwork. I thought about it more carefully and mentioned a shoulder injury that had ended my career as a baseball pitcher but otherwise had never bothered me. Dr. Sanchez seemed unimpressed, but the discussion prompted him to ask of any other orthopedic problems. Since childhood, my right knee has popped when I move my leg in just the right way, but the popping knee had never bothered me (and now, at 70, still hasn't). It must have sounded scarier than it was, because the doctor's eyes widened when he heard the snap, and in that instant I was deemed physically unfit to serve, classified 4-F. I could barely contain my euphoria, and after gathering my belongings, I headed for the nearest bar to celebrate my freedom. Thank you, Dr. Sanchez.
Suddenly, I was forced to think seriously about what to do with a newfound life. I wanted adventure and I wanted to continue my education in biology. While a graduate student at Washington State University, I had developed a friendship with Professor Vincent Schultz, a statistical ecologist and consultant to the Atomic Energy Commission (AEC). The Cold War was in full force, and the AEC was actively engaged in underground nuclear testing. Most of these tests were done at the Nevada test site, about 65 miles from Las Vegas. But the AEC wanted to test a much larger device, and they needed a more remote place to do that. The chosen site was Amchitka Island in the western Aleutian archipelago.
Amchitka was about as far from human habitation as one can get within the U.S. territorial boundary. It also had a fine deep-water harbor and a long and still functional runway built in World War II, during staging for the invasion of Japan. But the proposed test was deeply unpopular, especially in Alaska, where the AEC's credibility had been strained by Operation Chariot (O'Neill, 2007). The perils of radiation were well known and there was concern that the detonation of such a powerful blast might vent to the atmosphere or leak into the surrounding ocean, thus contaminating the rich North Pacific fishery and posing a health risk to people in Alaska as the imagined radioactive cloud drifted eastward with prevailing winds. There were also concerns over the impact of such a powerful detonation on the environment of Amchitka itself, which was part of the Alaska Maritime National Wildlife Refuge and home to numerous species, including an abundant sea otter population. The welfare of these animals had become a point of particular concern and controversy. The AEC asked Vince Schultz to help them find someone who could measure these impacts, and in June he called to ask if I wanted the job. By early October I was off to the Aleutians, intent on spending the next two years with sea otters at Amchitka Island.
I never imagined at the time that this early experience would lead to a life of such opportunity and adventure. I've returned to the Aleutian Islands nearly every year since, fascinated by the ecology and natural history of the place and following one question after another as my understanding of ecological concepts and the natural history of the area grew. Almost 45 years later, as I sit down to write this book, my goal is twofold. First and foremost, I wish to recount the science — the patterns of nature that I have endeavored to understand, what I have learned, and how I learned those things. Most of this has been published in the scientific literature, and some of it has been recounted in various textbooks and other secondary sources. This book is not a rehash but rather an integrated overview built around my own history and the history of the region. My personal history is important because it defines a chronology of discovery and understanding as one step slowly and often unexpectedly led to the next. The region's history is important because it affords a window for understanding the science. My second goal is to explain how the science really happened. Although I had what I thought was a clear and exciting vision from early on, the truth is that my vision changed markedly along the way, informed by fortuitous meetings with a few key individuals and the serendipitous influence of events that could never have been foreseen or understood as relevant at the time. Every scientist is deeply influenced by these latter kinds of experiences, but few ever write about them. As a result, the lay public and even nascent scientists have distorted views of the way interesting science is commonly done.
This book uses sea otters and kelp forests as examples to demonstrate ecological processes, in particular how species are linked together in food webs and the dynamic properties of the linkages. Tracing these patterns is relatively easy, requiring only the ability to identify species and the patience to watch, or otherwise figure out, who is eaten by whom. Understanding the dynamic properties of these linkages (the process of nature) is more complex and much more challenging. For example, for each particular consumer–prey linkage, we would like to know (a) to what extent the distribution and abundance of the consumer are influenced by the prey and (b) to what extent the distribution and abundance of the prey are influenced by the consumer. We'd like to know how these direct linkages of consumer and prey are themselves linked in food chains and — given the nearly infinite number of potential such pathways in the resulting food web — which of those that actually exist really matter. And we'd like to know how these systems were assembled over the long sweep of time, the reciprocity between ecology and evolution that played out during that assembly, and the degree to which ecosystems are being disassembled or rearranged by the pervasive hand of human influence.
The challenge in understanding dynamic process is that these forces of nature are invisible to the glance, and can remain unseen no matter how intently one looks. Only by experimentally perturbing the distribution and abundance of species can we see and understand the linkages between them. And therein lies the magic of the Aleutian Islands and their surrounding kelp forests. Unlike tropical rainforests or coral reefs, these kelp forests contain relatively few species. In contrast to most tropical islands, the topography and prevailing winds of the Aleutians have little or no influence on biotic communities, adding further to the biological simplicity of these islands. Also in contrast to tropical islands, the ubiquitous scouring influence of Pleistocene glaciers has largely eliminated regional variation from the evolution of island endemic species. What we have instead are hundreds of intrinsically similar islands, differing from one another largely as a consequence of the things people have done to them. These are the perturbations that make the Aleutians such a marvelous place for learning about the dynamics of nature.
My particular object of interest has been the sea otter and how this predator influences the structure and organization of food webs in kelp forests. Sea otters once occurred in abundance across the North Pacific rim but were hunted almost to extinction during the Pacific maritime fur trade. By 1911, when sea otters were finally protected from further takes, only two or three of the Aleutian Islands supported small remnant populations. They were extinct elsewhere. With protection, the remnant populations began to recover and spread. Almost 60 years later, when I arrived on the scene, sea otter populations had recovered to historical levels at some islands, were at various stages of recovery at others, and remained absent from still others. This is the perturbation I have used to explore the sea otter's influence on kelp forest food webs. In the beginning I simply compared rocky reef communities between islands with and without sea otters. Later my colleagues and I expanded that approach to southeast Alaska and British Columbia. In the mid-1970s I began watching systems change as they were reinvaded by sea otters when the populations of the latter increased and spread. Then, in the mid-1990s, I watched these changes run in reverse as sea otter populations suddenly collapsed, apparently after they were discovered and gobbled up by killer whales.
Much earlier in life, as I looked forward to a career in science, the prescription for success seemed vague and daunting. Looking back now, it all seems clear and simple. Thus, the book is structured as an account of how my career unfolded and the things I've learned along the way. Chapter 2 establishes the intellectual context of the story. Although sea otters and kelp forests provide the particulars, my work is really about large apex predators and their influences on ecosystems. I explain in detail the conceptual issues, the challenges to understanding these issues, the approaches scientists have taken in an effort to gain understanding, and why it is important. In chapter 3, I move to a specific focus on the natural and human history of the Aleutian archipelago and how the essentials of these histories have made that place so interesting. Chapter 4 recounts my initial discovery of the sea otter's role in kelp forest community structure, beginning with my earlier perceptions after spending nearly a year on Amchitka Island and the exciting "aha moment" that came with my first short trip to Shemya Island the following summer.
After completing my graduate studies on sea otters and kelp forests, I was hired by the U.S. Fish and Wildlife Service to conduct research on arctic marine wildlife. My first assignment was to survey the abundance and distribution of Pacific walruses, with the understanding that further work on walruses and their arctic marine ecosystem would follow. Chapter 5 provides an overview of what I did, what I learned from it, and why those experiences led me back to sea otters and kelp forests. In chapter 6, I begin to lay out the questions and challenges that followed my earlier discovery of the sea otter's ecological role as a keystone species in kelp forest ecosystems. My original studies were done in one small corner of the North Pacific, thus begging the question of whether the same ecological processes occurred elsewhere. Chapter 7 is focused on efforts to assess generality and variation in those processes across the North Pacific Ocean and southern Bering Sea, and to understand how and why these systems change with changes in sea otter population density.
Like forests everywhere, kelp forests provide a home and important resources to numerous other species. In chapter 8, I explain the key processes involved in these associations and how they influence the behavior and population biology of certain species. The material covered through chapter 8 establishes a number of strong linkages, between species or between functional groups, that constitute ecological forces with expected evolutionary consequences if played out over large enough areas and sufficient lengths of time. In chapter 9, I recount what we know or suspect about the evolutionary consequences of sea otter predation. Although these explorations might have gone in any number of directions, my work was focused on how variation in food-chain length has influenced the coevolution of defense and resistance in plants and their associated herbivores, how these apparent effects have influenced the ecology and evolution of other kelp consumers, and how the coevolution of plants and their herbivores has influenced both the structure and dynamics of the kelp forest ecosystem.
My story to this point was scientifically exciting but politically benign. That all begins to change in chapter 10 with the unexpected collapse of sea otter populations in the Aleutians and the conclusion that killer whale predation was the likely cause. I will explain in detail what I saw (the beginnings of the sea otter collapse in southwest Alaska), what I did retrospectively in an effort to understand the cause, and why I concluded that the likely culprits were killer whales. Although this conclusion seemed to resonate well enough with most others in the scientific and management communities, it left the question of "why" unanswered. In chapter 11, I recount the data, analyses, and logic that led my colleagues and me to recognize that the declines of sea otter populations were only part of a larger collapse of other coastal-living marine mammals in the same region, and to conclude that post–World War II industrial whaling was the likely cause. That conclusion, to put it mildly, didn't resonate so well with others who had been working on these other species, which leads to chapter 12, "Whale Wars." This was my first exposure to the darker corners of science, and the experience was both intellectually shocking and emotionally devastating. Recognizing that many beliefs are difficult to understand by anyone but their beholders, I'll nonetheless recount some of the key events and my own interpretations of why this work became so controversial.
Chapter 13 moves back to science with an account of the seemingly unrelated interplay among introduced foxes, seabirds, and terrestrial plant communities in the Aleutian archipelago. The foxes were introduced as a substitute fur resource after sea otters had been hunted almost to extinction, so the fox story is legitimately part of the sea otter's ecological legacy. Chapter 14 looks beyond coastal ecosystems of the North Pacific to ask the big question: How much of what we know or believe about that system is unique to sea otters and kelp forests, and how much might apply to other species of apex predators and their ecosystems around the world? Chapter 15 is a retrospective on the science, focusing on approach, scale, and the larger conceptual issues that emerged from my years of work on the sea otter–kelp forest system. Chapter 16 ends the book with a look to the future. What are the prospects for sea otters and kelp forests; what more do we need to know about them and how might the next generation of scientists go about learning those things; and why should that matter to more than a handful of people?
My life as a naturalist and ecologist has taken me to numerous places across the Pacific basin, many of which are remote and poorly known. Familiarity with this geography is of more than passing interest, because most of my work is founded on contrasts between different places or on the patterns of change at particular places through time. The three maps that precede this chapter identify the locations of all place names mentioned in the book.
Part of my job as a scientist has been to write technical reports, papers, and books for a relatively narrow and well-defined audience of other professionals. This book is aimed in part at that same group of professionals, to give them an integrated overview of what I've learned through the years about sea otters and kelp forests. My approach is not to dwell on the technical details but to recount the concepts, ideas, and high points of discovery that tie nearly half a century of study together as an integrated whole. Within this circle of professional ecologists, my particular target audience is students and younger scientists. They are the ones who will carry ecology forward, and I want them to understand how my own contribution to that endeavor actually happened.
Excerpted from Serendipity by James A. Estes. Copyright © 2016 The Regents of the University of California. Excerpted by permission of UNIVERSITY OF CALIFORNIA PRESS.
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Table of Contents
1 In the Beginning 1
2 Understanding Nature 8
3 The Aleutian Archipelago 21
4 Sea Otters and Kelp Forests 28
5 A Toe in the Arctic Ocean 45
6 Return to Attu 60
7 Generality and Variation 83
8 A Serpentine Food Web 100
9 Sea Otters and the Red Queen: Plant-Herbivore Coevolution 120
10 Sea Otters and Killer Whales 141
11 Megafaunal Collapse 161
12 Whale Wars 179
13 Foxes and Seabirds 190
14 A Global Perspective 203
15 Retrospection 222
16 Looking to the Future 231