Ecological Consequences of Artificial Night Lighting

Directors

Preface

For people who care about the natural world, the unrelentingly destructive activities of humanity are all too familiar. Most of these are painfully obvious to anyone watching the transformation of long-appreciated landscapes. We know death by bulldozer when we see it.

Seeing may be the key. We are for the most part diurnal, and visual, and as we consider the transformation of the planet, mostly we envision changes that we are able to see by day. It is an inherent bias in our collective thinking. But as we light up the night, with ever more powerful lights, is it not obvious, giving the matter some thought, that we are wreaking havoc on creatures with physiologies far more delicate than ours, interfering with the lifeways of suites of organisms that have evolved over the millennia with a dependable pattern of light and dark? All this happens at times when most of us are sleeping. As the night is ever more brightly lit, at least we can close the shutters. But what of the animals and plants?

I imagine myself in the position of other creatures, unable to control or escape their environments, which we have controlled for them—whales subject to sonar far beyond any sound their ears were meant to accommodate, birds migrating thousands of miles, thrown off course by lights with no limits. We are ultimately deprived of their beauty as they die off by the millions, from our careless expansion into all realms of the Earth.

My own love for night started simply as an aesthetic appreciation, and over the last twenty-five years or so I have been every year more profoundly saddened by the glare foisted on us by brighter and brighter lights. Long ago, as an undergraduate student, I loved to walk the neighborhoods of Berkeley on windy autumn nights, catching glimpses of softly lit walls of books in beautiful libraries in beautiful old homes, on winding streets lined with old, shady trees. The wind, the trees, the books, the soft lights—they were solace and fodder for dreams of my own future. I cannot say that I considered back then that the streets were probably dark enough, the houses lit softly enough, for there still to be myriad creatures living in lush yards and nearby unbuilt hillsides. I was then studying chemistry and physics, later psychology and anthropology, and never thought about studying ecology, despite being deeply committed to protecting the environment. My lifelong love of trees and wild creatures—birds, caterpillars, lobsters, lizards—had not been nurtured into a career. (Even by then, the kind of success envisioned for the children of Beverly Hills did not require nature study. Indeed, it was not even an option.)

I went straight to law school after college. I had not yet found a discipline where I felt to be at home. After ten years of doing everything I could to avoid using my law degree except when it involved environmental protection, I reentered the academic world, looking to reclaim the part of myself that loved nature and to supplement that love with deeper knowledge. When a consortium of Russian business interests sought Western corporate support to perpetually light up the tundra with a giant space mirror, I had a visceral reaction, shared by millions I’m sure, to the prospect of farming and industrializing the Arctic—where would so many of the world’s birds gather to breed? As a student of biogeography I also wondered what such an assault would mean to the ecology of the tundra itself. My old, deep appreciation for night, and the feelings engendered by catching glimpses of other people’s lives in softly lit homes filled with books, had become an ecologically informed awareness of the importance of night to nonhuman creatures, which allowed for a deeper concern about their welfare as night is transformed into something akin to day.

Some people need science to be convinced. Others are moved by something different, something better elicited by words, art, or music. Only 150 years ago, Henry David Thoreau walked his woods and fields at ten o’clock in the evening—about the time for the early news—and discovered a world apart from that which he knew so well by day. The wholesale transformation of the Earth in this almost unfathomably short time is perhaps nowhere more evident than in considering night landscapes. Thank goodness for the writers who know nature, who can help us see, who can help us remember. The vignettes interspersed in this book are meant to remind the reader that what we take for granted as night is nothing like what a natural night should be. The descriptions share a common thread, an unspoken recognition that night is a place all its own.

This is a book of science. But if it also infuses a little bit of reverence back into the tasks associated with planning for the nighttime environment, then we will have done our job.

—CATHERINE RICH

Ten years ago, Catherine started asking a seemingly simple question—What happens to animals and plants when subjected to artificial night lighting? We were both students of geography at UCLA; she was finishing her M.A. and thinking about a dissertation topic. As logical a question as it seemed, information was not widely available, save for the well-known examples of sea turtles and birds.

We started collecting references, assembling bits of information from reports and articles, often incidental observations in writings on often unrelated topics. Other people were investigating questions about the effects of artificial light on plants and animals, but only a few had started to integrate findings across taxa.

Although the science supported the intuitive observation that lighting ecosystems would affect species, policymakers for the most part never considered the effects of artificial light on nature. In 1999, Catherine received a call from a distressed Fish and Game biologist concerned about a decorative lighting project proposed for the Vincent Thomas Bridge at the Port of Los Angeles. The proposal included high-powered spotlights aimed directly into the sky, and project proponents had given little or no thought to the environmental consequences. Through the nonprofit that we founded together, The Urban Wildlands Group, Catherine organized a group of scientists, both biologists and astronomers, to testify before the California Coastal Commission (which had asserted jurisdiction over the proposal after we brought it to their attention) about the potential adverse effects of lights on migratory birds and other wildlife. The commissioners were receptive to this information and denied the proposal. (Later a much more environmentally sensitive design was approved with our support.) It was evident that absent the sort of concerted effort to oppose this project, decisionmakers such as the appointed members of the California Coastal Commission and their staff lacked the scientific information necessary to evaluate the effects of artificial night lighting on ecosystems in their review of projects. Catherine and I have found this lack of information time and again as we consult to those trying to protect natural places—environmental assessment documents either do not consider the effects of artificial night lighting on biological resources or do so poorly.

After working with us in opposition to the original Vincent Thomas Bridge proposal, Bob Gent of the International Dark-Sky Association asked that we write a paper reviewing the effects of artificial lighting on nature, to help in his advocacy and outreach efforts and to counteract the resistance he met when raising the topic. A few such articles had already been published, and we did not think we could improve on them without the input of scientists with special expertise in this topic. So we decided instead to convene an international conference. With the support of the UCLA Institute of the Environment, its then-director Rich Turco, and several key funders, the Ecological Consequences of Artificial Night Lighting conference was held in February 2002 on the UCLA campus.

The conference was an effort made possible, or at least made easier, by the Internet. With our collection of scientific articles as a starting point, extensive Web searches allowed us to find scientists who were investigating aspects of this topic. Their response when contacted about a possible meeting was enthusiastic; all were eager to meet others with similar interests.

This book contains chapters by many of the presenters at the conference. Some chapters are written by experts who were not presenters.

If we were building a house instead of editing a book, Catherine would be the architect and finish carpenter, and I would be the general contractor. Like all teams, we have specialized to capitalize on our different strengths. She is the visionary, and I am thankful to have had the opportunity to be in on the project.

We owe a debt of gratitude to those who have made this book possible and who inspired and encouraged its development and publication. The authors of the chapters deserve special recognition for their unique contributions, for accommodating our editorial requests, and for their patience. We appreciate and acknowledge the reviewers of each of the chapters, whose comments and insights improved the book as a whole. Our heartfelt thanks go to Bernd Heinrich, Carl Safina, and Phil DeVries for embracing the topic and generously agreeing to write about their experiences of the night.

We confirmed nearly all of the citations in the book to the original source, a task that would have been insurmountable without UCLA’s amazing collections and librarians. We are especially grateful to the interlibrary loan staff for processing scores of requests for obscure books, unpublished reports, and journal articles in several languages. We are indebted to the UCLA Department of Geography for providing uninterrupted access to library and academic Internet resources. Our research assistant, Sarah Casia, tracked down and copied references quickly and accurately. Attorney and friend Jonathan Kirsch graciously provided advice about publishing a book.

At Island Press we found editors, Barbara Dean and Laura Carrithers, who shared our enthusiasm for the subject and have helped us to shape a book to best convey this information.

We deeply appreciate the efforts of those who are working, or have worked, in the trenches on this issue: Virginia Brubeck and the many other agency staff members who have fought to protect species and habitats from the adverse effects of artificial night lighting, sometimes to their own detriment; Bob Gent, Dave Crawford, Jack Sales, and others involved with the International Dark-Sky Association who have eagerly incorporated these issues into their important work to protect the night sky; Michael Mesure and the Fatal Light Awareness Program for having the fortitude to document the incredible losses of migratory birds from collisions with buildings, both day and night; and countless others working to protect species and habitats from the deleterious effects of artificial night lighting.

The Conservation and Research Foundation provided a grant for the preparation of the book, a vote of confidence that we appreciate greatly. The Biological Resources Division of the U.S. Geological Survey provided a generous grant supporting publication.

A few individuals deserve special recognition. Larry and Sara Wan have supported us across many realms, for years. They are a continuing source of inspiration. The late Cherryl Wilson—our neighbor and Catherine’s dear friend—for nearly twenty years recognized and nurtured Catherine’s gift for protecting what is good in the world. Cherryl’s interest in protecting the beauty of the night, shared and enhanced by her life partner George Eslinger, seamlessly blended with our interest in saving the night for nature. We thank George, too, for years ago offering a research site to Catherine for a dissertation that was not to be, for continuing to provide technical assistance by phone at any hour, and for his friendship.

Our parents have provided support in many ways, from generous financial contributions, to helping edit chapters while visiting us from Maine, to caring about each deadline and encouraging our progress. My parents are both research biologists; Catherine’s mother is a dancer and choreographer and her father is a television director. As we look over the manuscript, we see their influence.

—TRAVIS LONGCORE

Chapter 1

Introduction

Catherine Rich and Travis Longcore

What if we woke up one morning only to realize that all of the conservation planning of the last thirty years told only half the story—the daytime story? Our diurnal bias has allowed us to ignore the obvious, that the world is different at night and that natural patterns of darkness are as important as the light of day to the functioning of ecosystems.

There have always been naturalists with a preference for night, those who study bats and badgers, moths and owls, who awaken when the sun goes down (e.g., Ferris 1986, Ryden 1989). But as a whole, professional conservationists have yet to recognize the implications of the dramatic transformation of the nighttime environment by ever-increasing artificial lights, except for the few well-known situations that leave dead bodies on the ground.

Lighted towers and tall buildings so confuse migrating birds that they circle and die of exhaustion or of collisions with each other or the structures themselves. Sea turtle hatchlings attracted to coastal streetlights end up desiccated, crushed under foot and wheel, or killed by predators. Yet beyond these high-profile examples, the magnitude of the ecological consequences of artificial night lighting is only beginning to be known. But all indications are that unless we consider protection of the night, our best-laid conservation plans will be inadequate.

This book provides a scientific basis to begin addressing the challenge of conserving the nighttime environment, but it remains critically necessary to expand basic research into the effects of altered light regimes on species and ecosystems.

The chapters here are meant to complement ongoing efforts to reduce, for other reasons, unnecessary and wasteful lighting. Loss of the view of the night sky across the developed world saddens poets and frustrates backyard astronomers (Riegel 1973). Excessive and improperly shielded lighting burdens society with the economic and environmental costs of wasted energy. These important issues are not addressed in detail here; rather, this book concentrates on the effects of artificial night lighting on nonhuman species and ecosystems.

A History of Artificial Light Ecology

Humans have long manipulated nighttime lighting levels, often with the intention of affecting wildlife behavior. Stoking the campfire at night has kept predators at bay since prehistoric times. As with many destructive human activities, the awareness that nighttime illumination might harm the natural world has developed relatively recently as technological innovations have facilitated a nearly unlimited ability to light the night. For birds, concern about needless deaths at lighthouses and other lights was expressed in the late 1800s and increased through the early 1900s (see Chapter 4, this volume). For other taxa, only the recent rapid urbanization of the developed world has resulted in sufficient effects to stimulate investigation.

The attraction of many groups of animals to light has been well known and documented since Aristotle (The History of Animals). Verheijen produced a monograph in 1958 that reviewed the mechanisms by which animals were attracted to lights, drawing on an extensive, predominantly European and Japanese literature dating from the late 1800s and early 1900s. Verheijen’s (1958) review documents the adverse effects of lights on wildlife, and in 1985 he proposed the term photopollution to mean artificial light having adverse effects on wildlife (Verheijen 1985:1). Also in the 1980s, Raymond (1984) raised concerns about the increasing problem of sea turtle disorientation from lights at beaches, which had been described earlier by McFarlane (1963; see Chapter 7, this volume). In 1988, Frank published a thorough review of the influence of artificial night lighting on moths. With the exception of Verheijen’s (1985) article, studies of the effects of artificial night lighting remained focused on single taxa. An approach integrating findings across different taxonomic groups that might be called artificial light ecology did not emerge.

Synthesis of the kind likely envisioned by Verheijen (1985) began in the 1990s. Alan Outen of the Hertfordshire Biological Records Centre produced a white paper, The Possible Ecological Implications of Artificial Night Lighting, in 1994, which he revised in 1997 and 1998 and published as a book chapter in 2002 (Outen 2002). The view that light pollution posed a broad problem for whole ecosystems remained largely in the gray literature, notably astronomer Arthur Upgren’s (1996) review published in the Natural Resources Defense Council’s magazine The Amicus Journal, and Wilson’s (1998) report for Environmental Building News. Witherington (1997) reviewed the deleterious effects of photopollution on sea turtles and other nocturnal animals and suggested that animal behaviorists could make an important contribution to conservation biology by studying biological photopollution. In Europe, public awareness of light pollution led to a series of reports and studies in the Netherlands in the late 1990s (Health Council of the Netherlands 2000, de Molenaar et al. 1997, 2000, 2003), several studies were completed and an academic conference was held in Germany (Scheibe 1999, Eisenbeis and Hassel 2000, Schmiedel 2001, Kolligs 2000), and a conference review was produced in France (Raevel and Lamiot 1998). In 2002 we convened the first North American conference on this topic, which provided the basis for this book.

Purpose and Scope

This book reviews the state of knowledge about the ecological consequences of artificial night lighting. The phrase ecological consequences of artificial night lighting communicates the essential elements that distinguish this field of inquiry from others. The term ecological consequences highlights that we are concerned with ecology. Because the term light pollution has come to be understood as referring to the degradation of human views of the night sky, we have largely avoided its use. We have found it helpful to distinguish between astronomical light pollution, in which stars and other celestial bodies are washed out by light that is either directed or reflected upward, and ecological light pollution, which disrupts ecosystems (Longcore and Rich 2004; Figure 1.1). The term artificial night lighting is meant to communicate our focus on light generated by human activity rather than on the effects of natural patterns of light and dark, although understanding natural conditions is central to describing disruptions.

Ecological light pollution includes direct glare, chronically increased illumination, and temporary, unexpected fluctuations in lighting. Sources of ecological light pollution include sky glow, lighted structures (e.g., office buildings, communication towers, bridges), streetlights, security lights, lights on vehicles, fishing boats, flares on offshore hydrocarbon platforms, and even lights on undersea research vessels (see Kochevar 1998). The phenomenon therefore involves potential effects across a range of spatial and temporal scales.

Figure 1.1. Diagram depicting ecological and astronomical light pollution. From Longcore and Rich (2004).

The extent of ecological light pollution is global (Figure 1.2; Elvidge et al. 1997). The first atlas of artificial night sky brightness illustrates that astronomical light pollution extends to every inhabited continent (Cinzano et al. 2001). Cinzano et al. (2001) calculated that only 56% of Americans live where it becomes sufficiently dark at night for the human eye to make a complete transition from cone to rod vision and that fully 18.7% of the terrestrial surface of the Earth experiences night sky brightness that is polluted by astronomical standards. As discussed in the chapters that follow, species and ecosystems may be affected by sky glow from distant sources. Furthermore, even shielded lights that are pointed down-ward, and thereby not contributing to sky glow, may have ecological consequences.

Figure 1.2. Distribution of artificial lights visible from space. Produced using cloud-free portions of low-light imaging data acquired by the U.S. Air Force Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS). Four types of lights are included: human settlements (cities, towns, and villages), fires (defined as ephemeral lights on land), gas flares, and heavily lit fishing boats. See Elvidge et al. (2001) for details. Image, data processing, and descriptive text by the National Oceanic and Atmospheric Administration’s National Geophysical Data Center.

As is evident in Figure 1.2, excessive lighting is associated with the wealthy countries of the world, places where people can afford to consume energy to illuminate the environment all night. The developing world, although supporting much higher population densities, is shown to be much darker at night, with fires used as lights rather than electric fixtures. The near absence of outdoor electric lighting across heavily populated regions of Africa illustrates this point.

Even in the developing world, however, industrial resource extraction is associated with artificial lighting. Flares from oil wells are visible off the coast of Nigeria, in otherwise dark regions of North Africa, and across the sparsely populated regions of Siberia. Lights from fishing vessels virtually eliminate night in the Sea of Japan and are visible off portions of the coasts of Southeast Asia and South America. This wasted, ecologically disruptive light is itself the end product of extractive and consumptive processes that are themselves environmentally damaging.

Units and Measurement

Illumination, or illuminance, is the amount of light incident per unit area; it is not the only measurement relevant to ecological light pollution, but it is the most commonly used. Light varies in its intensity (the number of photons per unit area) and in its spectral content (expressed by wavelength). Ideally, ecologists should measure illumination in photons per square meter per second, with associated measurements of the wavelengths of light present. More often, illumination is measured in lux (or footcandles, the non-SI unit), which expresses the intensity of light incident on a surface weighted for the spectral sensitivity of the human eye. The lux measurement places more emphasis on wavelengths of light that the human eye detects best and less on wavelengths that humans do not perceive as well. It is possible to avoid this human bias and adjust lux for the spectral sensitivity of other species, as done by Gal et al. (1999) for mysid shrimp. But because most engineering and planning professionals use lux, we use it as the measure of illuminance in this book. Table 1.1 illustrates familiar situations and their associated illumination. A sudden change in illumination is disruptive for some species (Buchanan 1993; see Chapters 2 and 9, this volume), so the percentage change in illumination, rate of change in illumination, or similar measures may be relevant.

Ecologists may measure luminance of light sources that are visible to organisms. Luminance is measured as the intensity of light per unit area of the source (e.g., candela/m²). How bright these sources appear to organisms depends on ambient conditions; in dark conditions a dim light appears very bright, whereas it would be practically invisible in daylight.

Table 1.1. Illumination from common sources.

Organization of the Book

We have divided the book into six parts, each addressing the effects of artificial night lighting on a taxonomic group. These divisions—mammals, birds, reptiles and amphibians, fishes, invertebrates, and plants—follow the subdisciplinary boundaries of modern zoology and botany defined by evolutionary relationships. They also follow the divisions of life described by Aristotle and Linnaeus without the benefit of modern evolutionary thought. In this division, some parts have more chapters than others, which reflects the unequal attention received by different groups. The taxonomic coverage is entirely disproportionate to the number of species in each group and does not reflect their importance in ecosystems. Little information is available about the effects of artificial light on marine mammals, for example, except for accounts of increased foraging on salmon by seals under artificial lights (Yurk and Trites 2000). Much work remains to be done to investigate the effects of artificial night lighting across the diversity of species on Earth.

Each section begins with a vignette about nature at night, either written specially for this book or excerpted from another source. The vignettes serve several purposes. They offer anecdotal observations of the ecology of organisms at night. From Henry David Thoreau’s moonlit walks to Bernd Heinrich’s night in the Maine woods, they illustrate that things are indeed different in the dark and that naturalists and scientists have recorded these differences for a long time. Anecdotal natural history observations such as these are often the source of scientific hypotheses. The vignettes are also meant to be evocative. We hope that an appreciation for the nature of night will remind lay and scientific readers alike why this topic is important.

Part I, on mammals, opens with Alexander von Humboldt’s account of the clamor of animals at night in the tropical rainforests of South America. He describes tumultuous activity during the full moon, especially by larger mammals.

Paul Beier’s chapter on terrestrial mammals provides insight into this phenomenon, reviewing many examples of the influence of lighting levels on predation risk and activity in mammals. He discusses the potential disruption of circadian, circalunar, and circannual cycles by artificial lighting and identifies situations in which artificial night lighting would be particularly hazardous to mammals.

Jens Rydell reports on the interaction between bats and insects at streetlights in Chapter 3. Although bats exploit the aggregations of insects attracted to streetlights, Rydell reports evidence that such lights are not necessarily beneficial to all bats. As with studies of small terrestrial mammals, competition and predation risk emerge as important factors restructuring and potentially reducing diversity in animal communities affected by outdoor lighting.

Bernd Heinrich’s account of nights outside growing up in Maine begins Part II on birds. He describes the transformation of the woods in the dark and the nocturnal flight song of the ovenbird. This species happens to be particularly vulnerable to death by collision with tall lighted structures during its nocturnal migration. Sidney A. Gauthreaux Jr. and Carroll G. Belser (Chapter 4) document this hazard to migratory birds through time, from lighthouses and lightships to today’s proliferating communication towers. They present the mechanisms of bird attraction to lights at night and report original research on the behavior of migratory birds around tall towers with different lighting types.

In Chapter 5, William A. Montevecchi addresses the risks of artificial night lighting to seabirds, including the uniquely dangerous flares of hydrocarbon platforms that both attract and incinerate birds. He considers direct, indirect, and cumulative effects of attraction to artificial light and provides detailed recommendations to reduce these effects, especially emphasizing the important role of independent observers in gathering useful data and enforcing compliance of regulations to protect birds.

Johannes G. de Molenaar, Maria E. Sanders, and Dick A. Jonkers contributed Chapter 6, which considers the effects of artificial night lighting on the nest choice and success of meadow birds during their breeding season. Their experiment in the Netherlands investigating the effect of roadway lighting on breeding black-tailed godwits has a before–after–control–impact design that is best suited to the investigation of this type of question but too rarely implemented. As they report, the small but statistically significant effect of lighting on breeding behavior was sufficient basis for the Dutch government to change the lighting system to reduce roadway illumination after peak traffic hours.

Reptiles and amphibians are the subject of Part III. David Ehrenfeld sets the tone in his reprinted essay on night and place from his research on sea turtles in Costa Rica. The darkness he describes, which is fundamental to the female turtle’s choice of nest site, has been eliminated by artificial light in many other places. Michael Salmon and his students and colleagues have long researched the effects of artificial lighting on sea turtles and their hatchlings. In Chapter 7, Salmon describes the lessons learned on Florida’s beaches—the interference with female nest site location and hatchling seafinding—and elaborates on the various solutions to reduce these effects, ranging from partial measures such as moving nests, to local controls on artificial night lighting, to comprehensive regional plans to restore darkness at nesting beaches.

Gad Perry and Robert N. Fisher discuss the effects of night lights on all other reptile groups (Chapter 8). They document how lights allow diurnal reptiles to extend activity into the nighttime and how nocturnal species may exploit aggregations of prey at lights. They also describe activity patterns that vary with moonlight and avoidance of moonlight in some species.

In Chapter 9, Bryant W. Buchanan describes the observed and potential effects of artificial night lighting on anuran amphibians. He considers the effects of chronic or dynamic shifts in illumination on behavior, physiology, and development. His own research, including a study to determine whether headlamps worn by researchers affect frog behavior and observations of the interruption of breeding choruses by artificial night lighting, provides important evidence of these effects.

Sharon E. Wise and Bryant W. Buchanan present the effects of artificial lighting on salamanders in Chapter 10. They draw on the extensive literature on salamanders and light from laboratory and field studies to describe changes in behavior and physiology resulting from artificial lighting, with consideration of its duration and spectral content. They include the results of several of their own unpublished experiments, including observations of salamanders in the field delayed in their foraging activity by an experimental treatment of dim light (ingeniously provided by a string of holiday lights).

Part IV concerns fishes. As the opening vignette by Carl Safina describes, changes in ambient illumination affect fish behavior. He reports the lore of old fishermen that the big fish are active during the full moon but avoid the new moon. The single chapter in this section (Chapter 11), by Barbara Nightingale, Travis Longcore, and Charles A. Simenstad, addresses the effects of artificial lighting on the bony fishes, with salmon species as exemplars. Nightingale et al. discuss the mechanism of fish vision and the response to light as influenced by age, species, ambient conditions, and lighting type. They describe the observed and potential effects of increased illumination on foraging and schooling, predator–prey relations, migration, reproduction, and harvest. More information about fishes is found in Chapter 15, which is primarily about aquatic invertebrates. The effects of artificial light on sharks, rays, and other lower vertebrates await future investigation.

Part V contains four chapters on invertebrates. Ecologist Philip J. DeVries wrote the opening essay on night and light in the tropics. He reminds us that many butterfly caterpillars feed at night and that the number of insects at lights decreases over time as they are consumed by predators and as the surrounding environment is destroyed.

In Chapter 12, Gerhard Eisenbeis discusses the attraction of flying insects in many taxonomic groups to streetlights. He classifies the effects that lights may have on insect behavior and considers the potential reduction in insect diversity around lights. He draws on his work with German colleagues to document and explain the patterns of insect death at streetlights in rural Germany, estimates total insect mortality from streetlights in Germany, and recommends lighting types to decrease such mortality.

Chapter 13 continues on this theme, as Kenneth D. Frank reports in detail the effects of outdoor lights on moths and moth populations. He explains the influence of artificial light on individual moths and works through the apparent contradiction that many moth species survive in heavily lit areas.

The effects of stray light on fireflies have the potential to be very different from those on other taxa. These bioluminescent beetles, which are the subject of Chapter 14 by James E. Lloyd, cue their behavior on ambient light intensity. In this chapter, Lloyd reviews the mechanisms by which light may interfere with the intraspecific and interspecific visual communication of firefly species. He also identifies needed research on this subject, listing useful projects that could be conducted by students.

Chapter 15 documents light pollution on freshwater lakes and its recorded and potential effects on invertebrates and their vertebrate predators. Marianne V. Moore, Susan J. Kohler, and Melani S. Cheers developed instrumentation to record nighttime illumination levels at lakes across an urban-to-rural gradient in New England. With these illumination levels, and incorporating previous research on the response of invertebrates and fishes to light, they predict the biological effects of light pollution on animals in the water column.

An excerpt from Henry David Thoreau’s essay Night and Moonlight begins Part VI, about plants. He describes how very differently he experiences the landscape and its plants and animals at night. Plants perceive light in the environment and respond to these cues physiologically. In Chapter 16, Winslow R. Briggs describes how plants detect light in the environment and some of the physiological responses of plants to light. Few published studies address the direct effects of artificial night lighting on plants, but Briggs reviews the mechanisms by which these effects would occur.

Our final chapter, Chapter 17, situates the examples of the book in the framework of ecology and identifies general mechanisms by which artificial night lighting influences species.

The range of ecological consequences of artificial night lighting is broad, including desynchronization of the mating flight of ants, disruption of the daily movement of zooplankton, altered nest site choice in breeding birds, interference with dispersal patterns of mammals, delay of the downstream migration of salmon, and disorientation and death of migratory birds. Many examples are found in the pages that follow, but much more remains to be learned. Only the imagination and creativity of current and future readers and researchers limits the questions that might be productively investigated.

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Part I

Mammals

Night, Venezuela

After eleven o’clock, such a noise began in the contiguous forest, that for the remainder of the night all sleep was impossible. The wild cries of animals rung through the woods. Among the many voices which resounded together, the Indians could only recognize those which, after short pauses, were heard singly. There was the monotonous, plaintive cry of the Aluates (howling monkeys), the whining, flute-like notes of the small sapajous, the grunting murmur of the striped nocturnal ape (Nyctipithecus trivirgatus, which I was the first to describe), the fitful roar of the great tiger, the Cuguar or maneless American lion, the peccary, the sloth, and a host of parrots, parraquas (Ortalides ), and other pheasant-like birds. Whenever the tigers approached the edge of the forest, our dog, who before had barked incessantly, came howling to seek protection under the hammocks. Sometimes the cry of the tiger resounded from the branches of a tree, and was then always accompanied by the plaintive piping tones of the apes, who were endeavouring to escape from the unwonted pursuit.

If one asks the Indians why such a continuous noise is heard on certain nights, they answer, with a smile, that the animals are rejoicing in the beautiful moonlight, and celebrating the return of the full moon. To me the scene appeared rather to be owing to an accidental, long-continued, and gradually increasing conflict among the animals. Thus, for instance, the jaguar will pursue the peccaries and the tapirs, which, densely crowded together, burst through the barrier of tree-like shrubs which opposes their flight. Terrified at the confusion, the monkeys on the tops of the trees join their cries with those of the larger animals. This arouses the tribes of birds who build their nests in communities, and suddenly the whole animal world is in a state of commotion. Further experience taught us, that it was by no means always the festival of moonlight that disturbed the stillness of the forest; for we observed that the voices were loudest during violent storms of rain, or when the thunder echoed and the lightning flashed through the depths of the woods. The good-natured Franciscan monk who (notwithstanding the fever from which he had been suffering for many months) accompanied us through the cataracts of Atures and Maypures to San Carlos, on the Rio Negro, and to the Brazilian coast, used to say, when apprehensive of a storm at night, May Heaven grant a quiet night both to us and to the wild beasts of the forest!

Alexander von Humboldt

From The Nocturnal Life of Animals in the Primeval Forest, Views of Nature, 1850.

Chapter 2

Effects of Artificial Night Lighting on Terrestrial Mammals

Paul Beier

All 986 species of bats, badgers and most smaller carnivores, most rodents (with the notable exception of squirrels), 20% of primates, and 80% of marsupials are nocturnal, and many more are active both night and day (Walls 1942). Thus it would be surprising if night lighting did not have significant effects on mammals. Compared with investigations on birds, lepidopterans, other insects, and turtles, however, few studies, or even anecdotal reports, document the effects of artificial night lighting on mammals in the wild. Because of the dearth of empirical evidence, this chapter begins with a review of the biology of mammalian vision, including the extensive literature on how moonlight affects nocturnal behavior of mammals and how light influences mammalian biological clocks. I then discuss several classes of likely effects of artificial night lighting on mammals, namely disruption of foraging patterns, increased predation risk, disruption of biological clocks, increased mortality on roads, and disruption of dispersal movements through artificially lighted landscapes. I include recommendations for experiments or observations that could advance our understanding of the most likely and significant effects.

Light and the Ecology and Physiology of Mammals

Insight into the potential consequences of artificial night lighting on mammals can be gained from an understanding of the activity patterns, visual ability, and physiological cycles of species under normal patterns of light and dark. Artificial light at night may disrupt the various daily, monthly, and annual cycles described in this