Ecological Light Pollution

Abstract

Ecologists have long studied the critical role of natural light in regulating species interactions, but, with limited exceptions, have not investigated the consequences of artificial night lighting. In the past century,the extent and intensity of artificial night lighting has increased such that it has substantial effects on the biology and ecology of species in the wild. We distinguish “astronomical light pollution”, which obscures the view of the night sky, from “ecological light pollution”, which alters natural light regimes in terrestrial and aquatic ecosystems. Some of the catastrophic consequences of light for certain taxonomic groups are well known, such as the deaths of migratory birds around tall lighted structures, and those of hatchling sea turtles disoriented by lights on their natal beaches. The more subtle influences of artificial night lighting on the behavior and community ecology of species are less well recognized, and constitute a new focus for research in ecology and a pressing conservation challenge.

Full text

As diurnal creatures, humans have long sought
methods to illuminate the night. In pre-industrial
times, artificial light was generated by burning various
materials, including wood, oil, and even dried fish.
While these methods of lighting certainly influenced
animal behavior and ecology locally, such effects were
limited. The relatively recent invention and rapid prolif-
eration of electric lights, however, have transformed the
nighttime environment over substantial portions of the
Earth’s surface.
Ecologists have not entirely ignored the potential dis-
ruption of ecological systems by artificial night lighting.
Several authors have written reviews of the potential
effects on ecosystems or taxonomic groups, published in
the “gray” literature (Health Council of the Netherlands
2000; Hill 1990), conference proceedings (Outen 2002;
Schmiedel 2001), and journal articles (Frank 1988;
Verheijen 1985; Salmon 2003). This review attempts to
integrate the literature on the topic, and draws on a con-
ference organized by the authors in 2002 titled Ecological
Consequences of Artificial Night Lighting. We identify the
roles that artificial night lighting plays in changing eco-
logical interactions across taxa, as opposed to reviewing
these effects by taxonomic group. We first discuss the scale
and extent of ecological light pollution and its relation-
ship to astronomical light pollution, as well as the mea-
surement of light for ecological research. We then address
the recorded and potential influences of artificial night
lighting within the nested hierarchy of behavioral and
population ecology, community ecology, and ecosystem
ecology. While this hierarchy is somewhat artificial and
certainly mutable, it illustrates the breadth of potential
consequences of ecological light pollution. The important
effects of light on the physiology of organisms (see Health
Council of the Netherlands 2000) are not discussed here.
Astronomical and ecological light pollution: scale
and extent
The term “light pollution” has been in use for a number
of years, but in most circumstances refers to the degrada-
tion of human views of the night sky. We want to clarify
that this is “astronomical light pollution”, where stars and
other celestial bodies are washed out by light that is
either directed or reflected upward. This is a broad-scale
phenomenon, with hundreds of thousands of light sources
cumulatively contributing to increased nighttime illumi-
nation of the sky; the light reflected back from the sky is
called “sky glow” (Figure 1). We describe artificial light
that alters the natural patterns of light and dark in ecosys-
tems as “ecological light pollution”. Verheijen (1985)
proposed the term “photopollution” to mean “artificial
light having adverse effects on wildlife”. Because pho-
topollution literally means “light pollution” and because
light pollution is so widely understood today to describe
the degradation of the view of the night sky and the
human experience of the night, we believe that a more
descriptive term is now necessary. Ecological light pollu-
tion includes direct glare, chronically increased illumina-
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REVIEWS REVIEWS REVIEWS
Ecological light pollution
Travis Longcore and Catherine Rich
Ecologists have long studied the critical role of natural light in regulating species interactions, but, with
limited exceptions, have not investigated the consequences of artificial night lighting. In the past century,
the extent and intensity of artificial night lighting has increased such that it has substantial effects on the
biology and ecology of species in the wild. We distinguish “astronomical light pollution”, which obscures
the view of the night sky, from “ecological light pollution”, which alters natural light regimes in terrestrial
and aquatic ecosystems. Some of the catastrophic consequences of light for certain taxonomic groups are
well known, such as the deaths of migratory birds around tall lighted structures, and those of hatchling sea
turtles disoriented by lights on their natal beaches. The more subtle influences of artificial night lighting
on the behavior and community ecology of species are less well recognized, and constitute a new focus for
research in ecology and a pressing conservation challenge.
Front Ecol Environ 2004; 2(4): 191–198
The Urban Wildlands Group, PO Box 24020, Los Angeles, CA
90024-0020 (longcore@urbanwildlands.org)
In a nutshell:
•Ecological light pollution includes chronic or periodically
increased illumination, unexpected changes in illumination,
and direct glare
•Animals can experience increased orientation or disorienta-
tion from additional illumination and are attracted to or
repulsed by glare, which affects foraging, reproduction, commu-
nication, and other critical behaviors
•Artificial light disrupts interspecific interactions evolved in
natural patterns of light and dark, with serious implications for
community ecology

Ecological light pollution T Longcore and C Rich
tion, and temporary, unexpected fluctuations in light-
ing. Sources of ecological light pollution include sky
glow, lighted buildings and towers, streetlights, fishing
boats, security lights, lights on vehicles, flares on off-
shore oil platforms, and even lights on undersea
research vessels, all of which can disrupt ecosystems to
varying degrees. The phenomenon therefore involves
potential effects across a range of spatial and temporal
scales.
The extent of ecological light pollution is global
(Elvidge et al. 1997; Figure 2). 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) calculate that only
40% 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 18.7% of the
terrestrial surface of the Earth is exposed to night sky
brightness that is polluted by astronomical standards.
Ecosystems may be affected by these levels of illumina-
tion and lights that do not contribute to sky glow may
still have ecological consequences, ensuring that ecolog-
ical light pollution afflicts an even greater proportion of
the Earth. Lighted fishing fleets, offshore oil platforms,
and cruise ships bring the disruption of artificial night
lighting to the world’s oceans.
The tropics may be especially sensitive to alterations in
natural diel (ie over a 24-hour period) patterns of light
and dark because of the year-round constancy of daily
cycles (Gliwicz 1999). A shortened or brighter night is
more likely to affect tropical species adapted to diel pat-
terns with minimal seasonal variation than extratropical
species adapted to substantial seasonal variation. Of
course, temperate and polar zone species active only dur-
ing a portion of the year would be excluded from this gen-
eralization. Species in temperate zones will
also be susceptible to disruptions if they
depend on seasonal day length cues to trigger
critical behaviors.
Measurements and units
Measurement of ecological light pollution
often involves determination of illumination
at a given place. Illumination is the amount
of light incident per unit area – not the only
measurement relevant to ecological light pol-
lution, but the most common. Light varies in
intensity (the number of photons per unit
area) and spectral content (expressed by
wavelength). Ideally, ecologists should mea-
sure 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 footcan-
dles, the non-SI unit), which expresses the
brightness of light as perceived by the human
eye. The lux measurement places more emphasis on
wavelengths of light that the human eye detects best and
less on those that humans perceive poorly. Because other
organisms perceive light differently – including wave-
lengths not visible to humans – future research on ecolog-
ical light pollution should identify these responses and
measure light accordingly. For example, Gal et al. (1999)
calculated the response curve of mysid shrimp to light
and reported illumination in lux adjusted for the spectral
sensitivity of the species.
Ecologists are faced with a practical difficulty when
communicating information about light conditions. Lux
is the standard used by nearly all lighting designers, light-
ing engineers, and environmental regulators; communi-
cation with them requires reporting in this unit. Yet the
use of lux ignores biologically relevant information. High-
pressure sodium lights, for instance, will attract moths
because of the presence of ultraviolet wavelengths, while
low-pressure sodium lights of the same intensity, but not
producing ultraviolet light, will not (Rydell 1992).
Nevertheless, we use lux here, both because of the need
to communicate with applied professionals, and because
of its current and past widespread usage. As this research
field develops, however, measurements of radiation and
spectrum relevant to the organisms in question should be
used, even though lux will probably continue to be the
preferred unit for communication with professionals in
other disciplines.
Ecologists also measure aspects of the light environ-
ment other than absolute illumination levels. A sudden
change in illumination is disruptive for some species
(Buchanan 1993), so percent change in illumination,
rate, or similar measures may be relevant. Ecologists may
also measure luminance (ie brightness) of light sources
that are visible to organisms.
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Figure 1. Diagram of ecological and astronomical light pollution.
Astronomical light pollution reduces the
number of visible stars
Unshielded lights can cause both
astronomical and ecological light
pollution
Tall, lighted structures
are collision hazards
Shielded lights
reduce astronomical
light pollution but
may still cause
ecological light
pollution
Sky glow from cities
disrupts distant
ecosystems

T Longcore and C Rich Ecological light pollution
Behavioral and population ecology
Ecological light pollution has demonstrable effects on the
behavioral and population ecology of organisms in natural
settings. As a whole, these effects derive from changes in ori-
entation, disorientation, or misorientation, and attraction or
repulsion from the altered light environment, which in turn
may affect foraging, reproduction, migration, and communi-
cation.
Orientation/disorientation and attraction/repulsion
Orientation and disorientation are responses to ambient
illumination (ie the amount of light incident on objects in
an environment). In contrast, attraction and repulsion
occur in response to the light sources themselves and are
therefore responses to luminance or the brightness of the
source of light (Health Council of the Netherlands 2000).
Increased illumination may extend diurnal or crepuscular
behaviors into the nighttime environment by improving an
animal’s ability to orient itself. Many usually diurnal birds
(Hill 1990) and reptiles (Schwartz and Henderson 1991),
for example, forage under artificial lights. This has been
termed the “night light niche” for reptiles and seems benefi-
cial for those species that can exploit it, but not for their
prey (Schwartz and Henderson 1991).
In addition to foraging, orientation under artificial illumi-
nation may induce other behaviors, such as territorial
singing in birds (Bergen and Abs 1997). For the northern
mockingbird (Mimus polyglottos), males sing at night before
mating, but once mated only sing at night in artificially
lighted areas (Derrickson 1988) or during the full moon.
The effect of these light-induced behaviors on fitness is
unknown.
Constant artificial night lighting may also disorient
organisms accustomed to navigating in a dark environment.
The best-known example of this is the disorientation of
hatchling sea turtles emerging from nests on sandy beaches.
Under normal circumstances, hatchlings move away from
low, dark silhouettes (historically, those of dune vegeta-
tion), allowing them to crawl quickly to the ocean. With
beachfront lighting, the silhouettes that would have cued
movement are no longer perceived, resulting in disorienta-
tion (Salmon et al. 1995). Lighting also affects the egg-lay-
ing behavior of female sea turtles. (For reviews of effects on
sea turtles, see Salmon 2003 and Witherington 1997).
Changes in light level may disrupt orientation in noctur-
nal animals. The range of anatomical adaptations to allow
night vision is broad (Park 1940), and rapid increases in
light can blind animals. For frogs, a quick increase in illumi-
nation causes a reduction in visual capability from which
the recovery time may be minutes to hours (Buchanan
1993). After becoming adjusted to a light, frogs may be
attracted to it as well (Jaeger and Hailman 1973; Figure 3).
Birds can be disoriented and entrapped by lights at night
(Ogden 1996). Once a bird is within a lighted zone at
night, it may become “trapped” and will not leave the
lighted area. Large numbers of nocturnally migrating birds
are therefore affected when meteorological conditions
bring them close to lights, for instance, during inclement
weather or late at night when they tend to fly lower.
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© The Ecological Society of America www.frontiersinecology.org
Figure 2. Distribution of artificial lights visible from space. Produced using cloud-free portions of low-light imaging data acquired by
the US Air Force Defense Meteorological Satellite Program Operational Linescan System. Four types of lights are identified: (1)
human settlements – cities, towns, and villages (white), (2) fires – defined as ephemeral lights on land (red), (3) gas flares (green),
and (4) heavily lit fishing boats (blue). 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.

Ecological light pollution T Longcore and C Rich
Within the sphere of lights, birds may collide with each
other or a structure, become exhausted, or be taken by
predators. Birds that are waylaid by buildings in urban
areas at night often die in collisions with windows as they
try to escape during the day. Artificial lighting has
attracted birds to smokestacks, lighthouses (Squires and
Hanson 1918), broadcast towers
(Ogden 1996), boats (Dick and
Donaldson 1978), greenhouses, oil
platforms (Wiese et al. 2001), and
other structures at night, resulting
in direct mortality, and thus inter-
fering with migration routes.
Many groups of insects, of which
moths are one well-known example
(Frank 1988), are attracted to
lights. Other taxa showing the
same attraction include lacewings,
beetles, bugs, caddisflies, crane flies,
midges, hoverflies, wasps, and bush
crickets (Eisenbeis and Hassel
2000; Kolligs 2000; Figure 4).
Attraction depends on the spec-
trum of light – insect collectors use
ultraviolet light because of its
attractive qualities – and the char-
acteristics of other lights in the
vicinity.
Nonflying arthropods vary in their reaction to lights.
Some nocturnal spiders are negatively phototactic (ie
repelled by light), whereas others will exploit light if avail-
able (Nakamura and Yamashita 1997). Some insects are
always positively phototactic as an adaptive behavior and
others always photonegative (Summers 1997). In arthro-
pods, these responses may also be influenced by the frequent
correlations between light, humidity, and temperature.
Natural resource managers can exploit the responses of
animals to lights. Lights are sometimes used to attract fish
to ladders, allowing them to bypass dams and power plants
(Haymes et al. 1984). Similarly, lights can attract larval
fish to coral reefs (Munday et al. 1998). In the terrestrial
realm, dispersing mountain lions avoid lighted areas to
such a degree that Beier (1995) suggests installing lights to
deter them from entering habitats dead-ending in areas
where humans live.
Reproduction
Reproductive behaviors may be altered by artificial night
lighting. Female Physalaemus pustulosus frogs, for exam-
ple, are less selective about mate choice when light levels
are increased, presumably preferring to mate quickly and
avoid the increased predation risk of mating activity
(Rand et al. 1997). Night lighting may also inhibit
amphibian movement to and from breeding areas by stim-
ulating phototactic behavior. Bryant Buchanan (pers
comm) reports that frogs in an experimental enclosure
stopped mating activity during night football games,
when lights from a nearby stadium increased sky glow.
Mating choruses resumed only when the enclosure was
covered to shield the frogs from the light.
In birds, some evidence suggests that artificial night
lighting affects the choice of nest site. De Molenaar et al.
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Figure 4. Thousands of mayflies carpet the ground around a security light at Millecoquins
Point in Naubinway on the Upper Peninsula of Michigan.
Courtesy of PJ DeVries
Figure 3. Attraction of frogs to a candle set out on a small raft.
Illustration by Charles Copeland of an experiment in northern
Maine or Canada described by William J Long (1901). Twelve
or fifteen bullfrogs (Rana catesbeiana) climbed on to the small
raft before it flipped over.

T Longcore and C Rich Ecological light pollution
(2000) investigated the effects of roadway
lighting on black-tailed godwits (Limosa l.
limosa) in wet grassland habitats. Breeding
densities of godwits were recorded over 2
years, comparing lighted and unlighted con-
ditions near a roadway and near light poles
installed in a wet grassland away from the
road influence. When all other habitat fac-
tors were taken into account, the density of
nests was slightly but statistically lower up to
300 m away from the lighting at roadway and
control sites. The researchers also noted that
birds nesting earlier in the year chose sites
farther away from the lighting, while those
nesting later filled in sites closer to the lights.
Communication
Visual communication within and between
species may be influenced by artificial night
lighting. Some species use light to communi-
cate, and are therefore especially susceptible
to disruption. Female glow-worms attract males up to
45 m away with bioluminescent flashes; the presence of
artificial lighting reduces the visibility of these communi-
cations. Similarly, the complex visual communication
system of fireflies could be impaired by stray light (Lloyd
1994).
Artificial night lighting could also alter communication
patterns as a secondary effect. Coyotes (Canis latrans)
group howl and group yip-howl more during the new
moon, when it is darkest. Communication is necessary
either to reduce trespassing from other packs, or to assem-
ble packs to hunt larger prey during dark conditions
(Bender et al. 1996). Sky glow could increase ambient illu-
mination to eliminate this pattern in affected areas.
Because of the central role of vision in orientation and
behavior of most animals, it is not surprising that artificial
lighting alters behavior. This causes an immediate conser-
vation concern for some species, while for other species
the influence may seem to be positive. Such “positive”
effects, however, may have negative consequences within
the context of community ecology.
Community ecology
The behaviors exhibited by individual animals in
response to ambient illumination (orientation, disorien-
tation) and to luminance (attraction, repulsion) influ-
ence community interactions, of which competition and
predation are examples.
Competition
Artificial night lighting could disrupt the interactions of
groups of species that show resource partitioning across
illumination gradients. For example, in natural commu-
nities, some foraging times are partitioned among species
that prefer different levels of lighting. The squirrel
treefrog (Hyla squirrela) is able to orient and forage at
lighting levels as low as 10-5lux and under natural condi-
tions typically will stop foraging at illuminations above
10-3lux (Buchanan 1998). The western toad (Bufo
boreas) forages only at illuminations between 10-1and 10-5
lux, while the tailed frog (Ascaphus truei) forages only
during the darkest part of the night at below 10-5lux
(Hailman 1984). While these three species are not neces-
sarily sympatric (ie inhabiting the same area), and differ
in other niche dimensions, they illustrate the division of
the light gradient by foragers.
Many bat species are attracted to insects that congre-
gate around light sources (Frank 1988). Although it
may seem that this is a positive effect, the increased
food concentration benefits only those species that
exploit light sources and could therefore result in
altered community structure. Faster-flying species of
bats congregate around lights to feed on insects, but
other, slower-flying species avoid lights (Blake et al.
1994; Rydell and Baagøe 1996).
Changes in competitive communities occur as diurnal
species move into the “night light niche” (Schwartz and
Henderson 1991). This concept, as originally described,
applies to reptiles, but easily extends to other taxa, such as
spiders (Frank pers comm) and birds (Hill 1990; Figure 5).
Predation
Although it may seem beneficial for diurnal species to be
able to forage longer under artificial lights, any gains from
increased activity time can be offset by increased preda-
tion risk (Gotthard 2000). The balance between gains
from extended foraging time and risk of increased preda-
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Figure 5. Crowned hornbill (Tockus alboterminatus) hawking insects at a
light at the Kibale Forest National Park, Uganda.
Courtesy of PJ DeVries

Ecological light pollution T Longcore and C Rich
tion is a central topic for research on small mammals, rep-
tiles, and birds (Kotler 1984; Lima 1998). Small rodents
forage less at high illumination levels (Lima 1998), a ten-
dency also exhibited by some lagomorphs (Gilbert and
Boutin 1991), marsupials (Laferrier 1997), snakes
(Klauber 1939), bats (Rydell 1992), fish (Gibson 1978),
aquatic invertebrates (Moore et al. 2000), and other taxa.
Unexpected changes in light conditions may disrupt
predator–prey relationships. Gliwicz (1986, 1999) des-
cribes high predation by fish on zooplankton during nights
when the full moon rose hours after sunset. Zooplankton
had migrated to the surface to forage under cover of dark-
ness, only to be illuminated by the rising moon and sub-
jected to intense predation. This “lunar light trap”
(Gliwicz 1986) illustrates a natural occurrence, but unex-
pected illumination from human sources could disrupt
predator–prey interactions in a similar manner, often to
the benefit of the predator.
Available research shows that artificial night lighting
disrupts predator–prey relationships, which is consistent
with the documented importance of natural light regimes
in mediating such interactions. In one example, harbor
seals (Phoca vitulina) congregated under artificial lights to
eat juvenile salmonids as they migrated downstream; turn-
ing the lights off reduced predation levels (Yurk and Trites
2000). Nighttime illumination at urban crow roosts was
higher than at control sites, presumably because this helps
the crows avoid predation from owls (Gorenzel and
Salmon 1995). Desert rodents reduced foraging activity
when exposed to the light of a single camp lantern (Kotler
1984). Frank (1988) reviews predation by bats, birds,
skunks, toads, and spiders on moths attracted to artificial
lights. Mercury vapor lights, in particular, disrupt the
interaction between bats and tympanate moths by inter-
fering with moth detection of ultrasonic chirps used by
bats in echolocation, leaving moths unable to take their
normal evasive action (Svensson and Rydell 1998).
From these examples, it follows that community struc-
ture will be altered where light affects interspecific inter-
actions. A “perpetual full moon” from artificial lights will
favor light-tolerant species and exclude others. If the dark-
est natural conditions never occur, those species that max-
imize foraging during the new moon could eventually be
compromised, at risk of failing to meet monthly energy
budgets. The resulting community structure would be sim-
plified, and these changes could in turn affect ecosystem
characteristics.
Ecosystem effects
The cumulative effects of behavioral changes induced by
artificial night lighting on competition and predation
have the potential to disrupt key ecosystem functions.
The spillover effects from ecological light pollution on
aquatic invertebrates illustrates this point. Many aquatic
invertebrates, such as zooplankton, move up and down
within the water column during a 24-hour period, in a
behavior known as “diel vertical migration”. Diel vertical
migration presumably results from a need to avoid preda-
tion during lighted conditions, so many zooplankton for-
age near water surfaces only during dark conditions
(Gliwicz 1986). Light dimmer than that of a half moon
(<10-1lux) is sufficient to influence the vertical distribu-
tion of some aquatic invertebrates, and indeed patterns of
diel vertical migration change with the lunar cycle
(Dodson 1990).
Moore et al. (2000) documented the effect of artificial
light on the diel migration of the zooplankton Daphnia in
the wild. Artificial illumination decreased the magnitude
of diel migrations, both in the range of vertical movement
and the number of individuals migrating. The researchers
hypothesize that this disruption of diel vertical migration
may have substantial detrimental effects on ecosystem
health. With fewer zooplankton migrating to the surface
to graze, algae populations may increase. Such algal
blooms would then have a series of adverse effects on
water quality (Moore et al. 2000).
The reverberating effects of community changes caused
by artificial night lighting could influence other ecosys-
tem functions. Although the outcomes are not yet pre-
dictable, and redundancy will buffer changes, indications
are that light-influenced ecosystems will suffer from
important changes attributable to artificial light alone
and in combination with other disturbances. Even
remote areas may be exposed to increased illumination
from sky glow, but the most noticeable effects will occur
in those areas where lights are close to natural habitats.
This may be in wilderness where summer getaways are
built, along the expanding front of suburbanization, near
the wetlands and estuaries that are often the last open
spaces in cities, or on the open ocean, where cruise ships,
squid boats, and oil derricks light the night.
Conclusions
Our understanding of the full range of ecological conse-
quences of artificial night lighting is still limited, and the
field holds many opportunities for basic and applied
research. Studies of natural populations are necessary to
investigate hypotheses generated in the laboratory, evi-
dence of lunar cycles in wild populations, and natural his-
tory observations. If current trends continue, the influ-
ence of stray light on ecosystems will expand in
geographic scope and intensity. Today, 20% of the area of
the coterminous US lies within 125 m of a road (Riiters
and Wickham 2003). Lights follow roads, and the propor-
tion of ecosystems uninfluenced by altered light regimes
is decreasing. We believe that many ecologists have
neglected to consider artificial night lighting as a relevant
environmental factor, while conservationists have cer-
tainly neglected to include the nighttime environment in
reserve and corridor design.
Successful investigation of ecological light pollution
will require collaboration with physical scientists and
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T Longcore and C Rich Ecological light pollution
engineers to improve equipment to measure light charac-
teristics at ecologically relevant levels under diverse field
conditions. Researchers should give special considera-
tion to the tropics, where the constancy of day–night
lighting patterns has probably resulted in narrow niche
breadths relative to illumination. Aquatic ecosystems
deserve increased attention as well, because despite the
central importance of light to freshwater and marine
ecology, consideration of artificial lighting has so far
been limited. Research on the effects of artificial night
lighting will enhance understanding of urban ecosystems
– the two National Science Foundation (NSF) urban
Long Term Ecological Research sites are ideal locations
for such efforts.
Careful research focusing on artificial night lighting will
probably reveal it to be a powerful force structuring local
communities by disrupting competition and predator–prey
interactions. Researchers will face the challenge of disen-
tangling the confounding and cumulative effects of other
facets of human disturbance with which artificial night
lighting will often be correlated, such as roads, urban
development, noise, exotic species, animal harvest, and
resource extraction. To do so, measurements of light dis-
turbance should be included routinely as part of environ-
mental monitoring protocols, such as the NSF’s National
Ecological Observatory Network (NEON). Future
research is likely to reveal artificial night lighting to be an
important, independent, and cumulative factor in the dis-
ruption of natural ecosystems, and a major challenge for
their preservation.
Ecologists have studied diel and lunar patterns in the
behavior of organisms for the greater part of a century (see
Park 1940 and references therein), and the deaths of birds
from lights for nearly as long (Squires and Hanson 1918).
Humans have now so altered the natural patterns of light
and dark that these new conditions must be afforded a
more central role in research on species and ecosystems
beyond the instances that leave carcasses on the ground.
Acknowledgements
We thank PJ DeVries for his photographs, and B Tuttle
and C Elvidge for the satellite image. Research was sup-
ported in part by the Conservation and Research
Foundation. We are grateful for constructive comments
and advice from W Briggs, BW Buchanan, KD Frank, JE
Lloyd, JR Longcore, MV Moore, WA Montevecchi, G
Perry, and M Salmon.
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