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Although the invention and widespread use of artificial light is clearly one of the most important human technological advances, the transformation of nightscapes is increasingly recognized as having adverse effects. Night lighting may have serious physiological consequences for humans, ecological and evolutionary implications for animal and plant populations, and may reshape entire ecosystems. However, knowledge on the adverse effects of light pollution is vague. In response to climate change and energy shortages, many countries, regions, and communities are developing new lighting programs and concepts with a strong focus on energy efficiency and greenhouse gas emissions. Given the dramatic increase in artificial light at night (0 -20% per year, depending on geographic region), we see an urgent need for light pollution policies that go beyond energy efficiency to include human well-being, the structure and functioning of ecosystems, and inter-related socioeconomic consequences. Such a policy shift will require a sound transdisciplinary understanding of the significance of the night, and its loss, for humans and the natural systems upon which we depend. Knowledge is also urgently needed on suitable lighting technologies and concepts which are ecologically, socially, and economically sustainable. Unless managing darkness becomes an integral part of future conservation and lighting policies, modern society may run into a global self-experiment with unpredictable outcomes.
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Copyright © 2010 by the author(s). Published here under license by the Resilience Alliance.
Hölker, F., T. Moss, B. Griefahn, W. Kloas, C. C. Voigt, D. Henckel, A. Hänel, P. M. Kappeler, S. Völker,
A. Schwope, S. Franke, D. Uhrlandt, J. Fischer, R. Klenke, C. Wolter, and K. Tockner. 2010. The dark side
of light: a transdisciplinary research agenda for light pollution policy. Ecology and Society 15(4): 13.
[online] URL: http://www.ecologyandsociety.org/vol15/iss4/art13/
Perspective
The Dark Side of Light: A Transdisciplinary Research Agenda for Light
Pollution Policy
Franz Hölker
1
, Timothy Moss
2
, Barbara Griefahn
3
, Werner Kloas
1
, Christian C. Voigt
4
,
Dietrich Henckel
5
, Andreas Hänel
6
, Peter M. Kappeler
7
, Stephan Völker
8
, Axel Schwope
9
,
Steffen Franke
10
, Dirk Uhrlandt
10
, Jürgen Fischer
11
, Reinhard Klenke
12
, Christian Wolter
1
, and
Klement Tockner
1,13
ABSTRACT. Although the invention and widespread use of artificial light is clearly one of the most
important human technological advances, the transformation of nightscapes is increasingly recognized as
having adverse effects. Night lighting may have serious physiological consequences for humans, ecological
and evolutionary implications for animal and plant populations, and may reshape entire ecosystems.
However, knowledge on the adverse effects of light pollution is vague. In response to climate change and
energy shortages, many countries, regions, and communities are developing new lighting programs and
concepts with a strong focus on energy efficiency and greenhouse gas emissions. Given the dramatic
increase in artificial light at night (0 - 20% per year, depending on geographic region), we see an urgent
need for light pollution policies that go beyond energy efficiency to include human well-being, the structure
and functioning of ecosystems, and inter-related socioeconomic consequences. Such a policy shift will
require a sound transdisciplinary understanding of the significance of the night, and its loss, for humans
and the natural systems upon which we depend. Knowledge is also urgently needed on suitable lighting
technologies and concepts which are ecologically, socially, and economically sustainable. Unless managing
darkness becomes an integral part of future conservation and lighting policies, modern society may run
into a global self-experiment with unpredictable outcomes.
Key Words: artificial light; energy efficiency; lighting concept; light pollution; nightscape; policy;
sustainability; transdisciplinary
INTRODUCTION
In 2009, the UN’s Year of Astronomy drew
worldwide attention to an area affected by a long
neglected environmental stressor: the increasing
illumination of our nightscapes. The Year of
Astronomy coincided with the 400th anniversary of
Galileo’s first observations with a telescope in
Padua. However, to look at today’s firmament
Galileo would have to escape to remote areas for
his research. This is because the Earth has become
brighter at night. The rapid proliferation of electric
lights has drastically reordered nightscapes across
the globe, in terms of both light intensity and light
spectrum (Cinzano et al. 2001, Elvidge et al. 2007).
Although artificial lighting has clearly enhanced the
quality of human life (Jakle 2001, Doll et al. 2006),
the benefits are accompanied by hidden costs.
Astronomers were the first to recognize that sky
glow hampers the detection of faint celestial objects,
obliging them to conduct their observations from
darker areas or from orbit (Riegel 1973, Smith
2009). It is only very recently that the multiple
negative effects of artificial lighting on ecology,
human health, and social well-being have gained
broader recognition (Jakle 2001, Rich and Longcore
2006, Navara and Nelson 2007).
1
Leibniz Institute of Freshwater Ecology and Inland Fisheries, Berlin,
2
Leibniz Institute for Regional Development and Structural Planning, Erkner,
3
Leibniz
Research Centre for Working Environment and Human Factors, Dortmund,
4
Leibniz Institute for Zoo and Wildlife Research, Berlin,
5
Technische Universität
Berlin, Department of Urban and Regional Planning,
6
Dark Sky Germany, Museum am Schölerberg, Osnabrück,
7
Leibniz Institute for Primate Research,
Göttingen,
8
Technische Universität Berlin, Department of Energy and Automation Technology, Berlin,
9
Astrophysikalisches Institut Potsdam,
10
Leibniz
Institute for Plasma Science and Technology, Greifswald,
11
Freie Universität Berlin, Institute for Space Sciences,
12
Helmholtz Centre for Environmental
Research, UFZ, Leipzig,
13
Freie Universität Berlin, Institute for Biology
Ecology and Society 15(4): 13
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Light pollution is now a widely accepted term for
adverse effects of artificial light on nature and
humans (Longcore and Rich 2004, Navara and
Nelson 2007). Nearly all living organisms,
including human beings, have evolved under a
natural rhythm of day and night. Interestingly,
around 30% of all vertebrates and more than 60%
of all invertebrates world-wide are nocturnal
(Hölker et al. 2010). As lighting becomes brighter
and extends farther into rural areas and offshore in
marine systems (see Appendix 1), the distinction
between day and night becomes blurred. Our
understanding of the adverse effects of light
pollution is vague and based mostly on purely
observational case studies. Nonetheless, there is
clear evidence that artificial lighting can alter
physiology, including hormonal balance, as well as
behavior, orientation, organism fitness, food web
interactions, and biotope connectivity (Rich and
Longcore 2006, Navara and Nelson 2007). The
artificial disturbance of the natural day/night cycle
may, as a result, have serious psycho-physiological
and even medical consequences for humans, along
with ecological and evolutionary implications for
animals, plants, and even entire terrestrial,
freshwater, and marine ecosystems (Rich and
Longcore 2006, Navara and Nelson 2007). Light
pollution is most probably an important but
underestimated driver behind the erosion of
provisioning, e.g., loss of light-sensitive species and
genotypes; regulating, e.g., decline of nocturnal
pollinators such as moths and bats; and cultural
ecosystem services, e.g., loss of aesthetic values
such as the visibility of the Milky Way (Rich and
Longcore 2006, Carpenter et al. 2009, Smith 2009).
The principal effects become most apparent at the
interfaces between the physiological, ecological,
and socioeconomic realms (Fig. 1). The problem is
escalating worldwide as artificial lighting is rapidly
increasing by around 6% per year (range: 0-20%;
Table 1).
THE CURRENT FOCUS ON ENERGY
EFFICIENCY
Artificial lighting consumes 19% of total global
electricity, accounting for greenhouse gas
emissions of 1900 Mt of CO
2
per year (OECD/IEA
2006). It is no surprise that current artificial lighting
policies focus primarily on energy efficiency and
greenhouse gas emissions (e.g., OECD/IEA 2010),
although safety, astronomical, and other considerations
appear sporadically (see Appendix 2). The
International Energy Agency has calculated that the
systematic use of ‘least life-cycle cost’ lighting
solutions (see Appendix 3) from 2008 onward
would reduce the electricity consumption
attributable to lighting until 2020 by 1311 TWh and
763 Mt of CO
2
emissions per year compared to
projections on the basis of current policies (OECD/
IEA 2006).
Recently, the European Ecodesign Directive
established a framework to phase out the
incandescent lamp and other particularly energy-
intensive lighting products, e.g., high-pressure
mercury lamps (The European Parliament and the
Council of the European Union 2009). This step
could reduce CO
2
emissions in the EU by
approximately 42 Mt per year, corresponding
roughly to a 10% reduction of the greenhouse gas
emissions the EU promised to achieve under Kyoto
(Denneman 2009, Managenergy 2010). In the
United States, President Obama has proposed a
scheme for more energy-efficient lamps and
lighting equipment as part of his climate change
policy. This would result in savings of
approximately 20 Mt CO
2
annually (The White
House 2009). Similar activities are reported inter
alia for China, Australia, and New Zealand (OECD/
IEA 2006, 2010).
Within such policy frameworks, many countries,
regions, and communities are developing new
lighting programs and concepts. For example, the
EU has launched a number of programs, e.g.,
GreenLight www.eu-greenlight.org, E-Street
www
.e-streetlight.com, to adopt efficient lighting
systems and to initiate a permanent market
transition. Although most of these programs and
concepts are driven by energy efficiency motives
alone, there remain causes for concern. For
example, technological innovations that help
improve the efficiency of energy appliances and
systems often lead to greater energy use because of
direct ‘rebound’ effects (Herring and Roy 2007,
Charles 2009). New technologies and reduced costs
could generate steep increases in the overall use of
lighting and may stimulate innovative additional
uses for lighting (Herring and Roy 2007, Fouquet
and Pearson 2006). Lighting efficiency has doubled
over the past 50 years in the UK; however, per capita
electricity consumption for lighting increased
fourfold over the same period (Fouquet and Pearson
2006). Due to the development and use of new
lighting technologies, e.g., compact fluorescent
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Table 1. Pristine sites with natural sky background brightness can be identified by measuring the sky
background (astronomical unit mag/arcsec² in the visual range corresponds to a negative logarithmic scale
of sky luminance) at modern astronomical observatories. Older observatories were built at dark sites close
to cities. Today, these peri-urban sites are characterized by bright skies. Some observatories in the southwest
of the USA were able to preserve relatively dark skies because of lighting ordinances (low pressure sodium
lamps, full cut-off luminaires) in the nearby cities, resulting in a decrease of sky brightness in Flagstaff,
Arizona since 1982 (Lockwood et al. 1990). The increase of the sky background depends on different
model assumptions for several observatories (Garstang 1989). Indirect values can be derived from the
increase of power consumption and lamp efficiency for street lighting.
Period Sky brightness (mag/
arcsec²)
Annual
increase
(%)
Cause References
Pristine
Mt. Graham, AZ, USA 2000 – 2008 21.5 – 21.8 0 solar activity Pedani 2009
Hawaii, USA 1986 – 1996 21.3 – 21.9 0 solar activity Krisciunas 1997
Cerro Tololo/Chile 1992 – 2006 22.0 – 21.2 0 solar activity Krisciunas et al. 2007
Kitt Peak/Mt. Hopkins,
AZ, USA
1988 – 1999 0.1 – 0.2 1 – 2 ordinances Massey and Foltz 2000
Urban
Flagstaff, AZ 1974 – 1982 0.4 5 Lockwood et al. 1990
IAO, India 2003 – 2007 21.3 – 21.1 5 Stalin et al. 2008
Mt. Wilson, USA 1973 – 1999 19.8 – 18.8 3.6 city lights
Los Angeles
Teare 2000
1900 – 2000 2.7 2.5 city lights
Los Angeles
Garstang 2004
Mt. Hamilton, CA, USA 1950 – 1975 21.9 – 20.6 5 city lights Walker 1973
Ekar, Asiago, Italy 1960 – 1995 21.6 – 20.2 10 city lights Cinzano 2000
G. Haro, Mexico 1994 – 1997 20.5 – 20.0 19 city lights Carrasco et al. 1998
NAO, Japan
1958/1978/1989
20.5/19.5/17.6 5 – 17 city lights
Tokyo
Isobe and Kosai 1998
Worldwide
Expert guess 3 Narisada and Schreuder
2004
(con'd)
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Indirect (energy consumption)
UK Campaign to Protect
Rural England (CPRE)
1993 – 2000 4 DMSP data CPRE 2003
UK McNeill 1984 – 1999 1.86x lmh 4.2 street light McNeill 1999
UK Fouquet/Pearson 1950 – 2000 5x lmh 3.3 overall
energy
consumption
for light
Fouquet and Pearson
2006
USA 1967 – 1970 20 energy +
efficiency
Riegel 1973
France 1990 – 2000 3 energy ADEME 2007
Germany 1950 – 1990 8 energy +
efficiency
Hänel 2001
Note: IAO India = Indian Astronomical Observatory, NAO Japan = National Astronomical Observatory
of Japan
lamp (CFL), light-emitting diode (LED), organic
light-emitting diode (OLED), we can expect a
dramatic drop in the cost of lighting services, a
desirable end in itself, but with possibly higher
energy consumption and wider loss of dark
nightscapes as a consequence. Technological
innovations should, therefore, not only save
consumers money, but also consider human health,
ecological, and socioeconomic aspects.
BEYOND ENERGY EFFICIENCY
Whereas air, noise, or water pollution have been
high priority policy issues for decades, light
pollution remains scientifically, culturally, and
institutionally in the dark. Given the dramatic
increase in artificial light in recent years, we see an
urgent need for research on the physiological,
human health, ecological, and socioeconomic
significance of the loss of the night that addresses
how illumination can be improved both technically
and institutionally yet having fewer adverse effects.
Managing darkness has to be an integral part of
future conservation planning and illumination
concepts. If not, our modern society may run into a
global self-experiment with unpredictable outcomes
(Fig.1).
Any attempts to reduce light pollution run up against
positive connotations of lighting which are deeply
ingrained in modern societies. Culturally, light is a
symbol of enlightenment, modernity, urbanity, and
security (Jakle 2001). Policy initiatives against light
pollution therefore need to take into consideration
the many advantages of artificial lighting, real and
perceived, for economic production, social
lifestyles, and security while at the same time
addressing its negative side effects. For this, a sound
understanding of the historical, socioeconomic, and
cultural reasons for the emergence and
dissemination of lighting systems is needed. We
then need to ask how far recent changes in attitudes,
in particular relating to the environment and human
health, are creating openings for a shift in policy
and practice. Part of this process involves
identifying and building up a coalition of interest
around the light pollution issue, incorporating such
diverse stakeholder groups as ecologists,
astronomers, and health professionals, but also
electricity utilities, lamp manufacturers, property
owners, local businesses, city planners, or those
concerned about nighttime security.
Thus, the research needed is transdisciplinary, i.e.
it should cut across boundaries between scientific
disciplines and between science, policy, and
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Fig. 1. Hypothetical impacts of exposure to artificial light at night. The main impacts, both with respect
to light intensity and color spectra, emerge at the interfaces between the different physiological,
ecological, and socioeconomic aspects.
practice and should address facts, practices, and
values (Wiesmann et al. 2008). The following
natural, social, and engineering science questions
are central to this research agenda:
What characteristics of light disrupt human
health and ecological communities?
How does light pollution interact with other
stressors such as air, water, and noise
pollution, or climate change?
What technologies can address the
environmental, health, and economic
disadvantages of current lighting practices in
different areas or settlement types?
Ecology and Society 15(4): 13
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What alternative lighting strategies and
policies are politically, culturally, and
economically viable?
To what extent are users willing to minimize
light pollution and adopt alternatives?
Such research should validate indicators and
guidelines, set priorities for human health and
environmental protection, identify technical and
economic possibilities for improvements in
lighting, and develop sustainable lighting concepts
and techniques for future nightscapes.
With our present understanding, there is little choice
but to develop guidelines in accordance with energy
efficiency criteria and the few available case studies
on the ecological and health impacts of lighting. The
Commission Internationale de l’Éclairage (CIE),
the International Dark-Sky Association (IDA; ww
w.darksky.org), and the Illuminating Engineering
Society of North America (IESNA 2000) provide
preliminary recommendations, illustrating how
local lighting ordinances and innovative designs
may promote low impact, energy-efficient and
aesthetically pleasing lighting systems (e.g., CIE
1997, 2000, 2003). Promising options are, for
example, lamps that direct their light more
accurately toward where it is needed, lamps that
emit light with a spectral distribution causing
minimal harm, timers and sensors to turn lights on
only when needed, and the consideration for light-
sensitive areas, especially the periphery of
residential areas, forests, parks, and shores of water
bodies. The comprehensive and transdisciplinary
research advocated here will result in more
advanced regulations and guidelines at, in
particular, the national level and the development
of intelligent, i.e., adaptive and context-dependent,
lighting concepts for local communities. These will
help countries, regions, and cities to maximize the
social and economic benefits of artificial light at
night, while minimizing its negative and unintended
ecological and health impacts. On this basis, future
generations will be able to experience nightscapes
comparable to those which Galileo knew without
having to travel to the Australian Outback or the
Chilean Andes.
Responses to this article can be read online at:
http://www.ecologyandsociety.org/vol15/iss4/art13/
responses/
Acknowledgments:
We are grateful to Steve Carpenter, Jens Krause,
Elisabeth K. Perkin, and Michael Monaghan for
helpful comments. This work was supported by
Milieu (FU Berlin), the Leibniz Association, the
Senatsverwaltung für Bildung, Wissenschaft und
Forschung, Berlin, and the Federal Ministry of
Education and Research, Germany.
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Appendix 1. Sources of light at night
Light pollution is a by-product of industrial civilization, which alters the natural patterns of
light and dark in ecosystems and includes direct glare, and chronically increased
illumination; all of which can disrupt terrestrial, freshwater, and marine ecosystems to
varying degrees (Longcore and Rich 2004).
Light pollution by urban development includes street lights, illuminated buildings,
bridges and towers, commercial advertising, factories, parking places, airports, flaring of
natural gas, sky beamer, illuminated sporting venues, and also car headlights. It is most
distinct in industrialized, densely populated areas of Europe, North America, and Japan
and in metropolises in the Middle East and North Africa (e.g. Cinzano et al. 2001,
Longcore and Rich 2004, Elvidge et al. 2007).
The main sources of artificial light in marine environments include vessels, lighthouses,
fisheries using light to attract fish (e.g. squid fisheries), as well as gas flares at oil and
gas platforms (offshore gas flaring) (e.g. Cinzano et al. 2001, Elvidge et al. 2007,
Elvidge et al. 2009).
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Appendix 2. Lighting guidelines and policies
Security is an important aspect in urban lighting guidelines. Various CIE (Commission
Internationale de l’Éclairage) technical reports exist on this topic (e.g. CIE 1995, 2000).
However, besides security aspects, pioneering regional laws have been introduced to
protect dark sky close to astronomical observatories. Methods to reduce sky glow were
defined by the IAU (International Astronomical Union) and the CIE (Cayral et al. 1980).
On the Canary Islands and in Chile, international observatories are protected by law
(Instituto de Astrofísica de Canarias (IAC) 1988, Ministerio de Economia, Fomento y
Reconstruccion 1998). The regional law of Lombardy, Italy, and the national law of
Slovenia are influenced by both energy efficiency and astronomical concerns (LR
Lombardia 17/2000, Uradni List 2007). The Fatal Light Awareness Program (FLAP) is an
example of efforts by cities (Toronto, in this case) to address the issue of light pollution that
links both energy efficiency and ecology; in this case bird conservation (FLAP 2010). The
Catalonian Law strives to restore and protect natural nighttime conditions for the benefit of
fauna, flora, and the general ecosystem (Font 2002).
LITERATURE CITED
Cayrel, R., F. G. Smith, A. J. Fisher, and J. B. de Boer. 1980. Guidelines for minimizing
urban sky glow near astronomical observatories. IAU/CIE, Paris.
Commission Internationale de l’Éclairage (CIE). 1995. Recommendations for the
lighting of roads for motor and pedestrian traffic. CIE Technical Report 115-1995, Vienna,
Austria.
Commission Internationale de l’Éclairage (CIE). 2000. Guide to the lighting of urban
areas. CIE Technical Report 136-2000, Vienna, Austria.
FLAP. 2010. Fatal Light Awareness Program. [online] URL:
http://www.flap.org/flap_home.htm.
Font, M. R. 2002. La ley catalana de ordenación ambiental del alumbrado para la
protección del medio nocturno. Autonomies 28, Barcelona.
Instituto de Astrofísica de Canarias (IAC). 1988. Ley Cielo 31/1988, Bol, Ofic, Est. 246.
[online] URL: http://www.iac.es/eno.php?op1=4&op2=10&lang=en
LR Lombardia 17/2000 (updated with D.G.R. Lombardia 2611/2000, L.R. Lombardia
38/2004 and the Regulations D.G.R. Lombardia 7/6162/2001). [online] URL:
http://cielobuio.org/index.php?option=com_content&view=article&id=471.
Ministerio de Economia, Fomento y Reconstruccion. 1998. Decreto Suprema No. 686,
Chile. [online] URL: http://www.opcc.cl/.
Uradni List. 2007. Republike Slovenije, St. 81. [online] URL:
http://www.uradni-list.si/1?year=2007&ofs=40.
Ecology and Society 15(4): 13
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Appendix 3. Life-cycle cost of a lighting system
The life-cycle cost of a lighting system is the sum of its initial cost (the sum of the purchase
price and the installation cost) and the discounted operating costs (the energy and
maintenance costs discounted over time to take account of the time-dependent value of
money). In this analysis a real discount rate of 5% is assumed (OECD/IEA 2006).
LITERATURE CITED
Organisation for Economic Co-operation and Development (OECD)/International
Energy Agency (IEA). 2006. Light’s labour’s lost - policies for energy-efficient lighting.
OECD/IEA, Paris, France.
... The nights on earth have been getting brighter since humans introduced artificial light at night (ALAN). Particularly, since technological advancements have made light more efficient, ALAN is financially affordable to many people and the extent of artificial illumination of the night is increasing every year (Hölker et al., 2010a, Kyba et al., 2017a. While humans make use of artificial light to expand their temporal activity range to a "24 h society", possible negative side effects of ALAN include increased incidence of cancer, metabolic syndrome, and mood disorders in humans (Walker et al., 2020) as well as an unintended impact on nature (Rich and Longcore, 2006). ...
... For example, day-active species often rely on their visual sense whereas night-active species have generally higher sensitivities in other sensory systems (olfactory, auditory) and special adaptations of the eyes for capturing low light incidence. Flora and fauna constantly adapt to environmental changes, but light pollution has been increasing by rates of 2 -6% globally, with rapidly developing areas of up to 20% more illuminated areas each year (Hölker et al., 2010a, Kyba et al., 2017a. Like other anthropogenic impacts, such dramatic changes may be too fast for most species to adapt. ...
... The natural darkness of nocturnal environments is disturbed by increasing levels of artificial illumination deriving from human activities (Hölker et al., 2010a, Kyba et al., 2017a. The daily recurring change from brightness to natural darkness is used as a source of information by most organisms to synchronize daily rhythms of metabolic and behavioral processes (Gaston et al., 2013, LeGates et al., 2014, Whitmore et al., 2000. ...
Thesis
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Künstliches Licht in der Nacht (ALAN) entsteht in Zentren menschlicher Aktivität und erhellt die Nacht, wodurch biologische Rhythmen von Menschen und Wildtieren gestört werden können. Skyglow ist eine diffuse Aufhellung des Nachthimmels aufgrund von Reflexion und Streuung von ALAN, welche indirekt große Bereiche (vor-)städtischer Ökosysteme beleuchtet. Da sich Zentren menschlicher Aktivität häufig in der Nähe von Flüssen und Seen befinden, kann sich Skyglow unverhältnismäßig stark auf wildlebende Tiere in Süßwassergebieten auswirken. In drei Experimenten wurden die Auswirkungen von ALAN auf die Physiologie des Europäischen Flussbarsches untersucht. Die Fische wurden verschiedenen Versuchsbedingungen ausgesetzt: 1) niedrige ALAN-Intensitäten von 0,01, 0,1 und 1 lx unter kontrollierten Bedingungen, 2) höhere ALAN-Intensitäten von 1, 10 und 100 lx unter kontrollierten Bedingungen und 3) eine niedrige ALAN-Intensität von 0,06 lx in einem Feldexperiment. In den vorgestellten Experimenten unterdrückten niedrige ALAN-Intensitäten den nächtlichen Melatoninspiegel sowie teilweise Reproduktionshormone bei Weibchen. Höhere ALAN-Intensitäten verringerten das aktivste Schilddrüsenhormon und das relative Lebergewicht der Fische. Diese Arbeit zeigt physiologische Veränderungen bereits bei schwachen ALAN-Intensitäten, wie sie in großen Bereichen (vor-)städtischer Ökosysteme in Form von Skyglow vorkommen. Die empfindlichste Reaktionsvariable auf die Belastung durch ALAN bei Fischen ist der nächtliche Melatoninspiegel. Mögliche Wirkungen von ALAN auf andere physiologische Parameter können durch direkten Lichteinfall oder indirekt über reduziertes Melatonin ausgelöst werden. Diese Arbeit trägt zum Verständnis der Schwellenwerte für verschiedene physiologische Effekte durch eine mehrwöchige ALAN-Exposition bei. Schwellenwerte für ALAN-Intensitäten könnten zukünftig notwendige Deskriptoren für die Ausarbeitung von regulierenden Maßnahmen zur Reduzierung von Lichtverschmutzung liefern.
... In the natural setting, earlier spring budburst (up to 7.5 days) 17 and later autumn senescence (by 13 to 22 days) 18,19 were found in areas exposed to ALAN using satellite observations. Besides being affected by direct light in the illuminated urban area (e.g., domestic, architectural, advertising, and public street lightings) 20 , plant phenology may also potentially be affected by low-intensity diffuse light from sky glow or transient light (e.g., vehicle lights) 21 . The latter occurs over much larger areas surrounding cities and transportation network 21 . ...
... The continuous increasing ALAN may have significant and far-reaching consequences in disrupting key ecosystem functions, ecological processes, and ecosystem services with a significant impact on human health and well being 46,54 . Although previous studies have advanced our understanding of ALAN effects on the behavior and physiology of animals 11,20 , its ecological impacts and their consequences for plants are far less studied 55 . Our study identified an opportunity for greater attention and focus on this area as an emerging topic in global change ecology, i.e., the effect of ALAN on ecosystems dynamics and its interaction with climate warming. ...
Article
Artificial light at night (ALAN), an increasing anthropogenic driver, is widespread and shows rapid expansion with potential adverse impact on the terrestrial ecosystem. However, whether and to what extent does ALAN affect plant phenology, a critical factor influencing the timing of terrestrial ecosystem processes, remains unexplored due to limited ALAN observation. Here we used the Black Marble ALAN product and phenology observations from USA National Phenology Network to investigate the impact of ALAN on deciduous woody plants phenology in the conterminous United States. We found that (1) ALAN significantly advanced the date of breaking leaf buds by 8.9 ± 6.9 days (mean ± SD) and delayed the coloring of leaves by 6.0 ± 11.9 days on average; (2) the magnitude of phenological changes was significantly correlated with the intensity of ALAN (P < 0.001); and (3) there was an interaction between ALAN and temperature on the coloring of leaves, but not on breaking leaf buds. We further showed that under future climate warming scenarios, ALAN will accelerate the advance in breaking leaf buds but exert a more complex effect on the coloring of leaves. This study suggests intensified ALAN may have far-reaching but under-appreciated consequences in disrupting key ecosystem functions and services, which requires an interdisciplinary approach to investigate. Developing lighting strategies that minimize the impact of ALAN on ecosystems, especially those embedded and surrounding major cities, is challenging but must be pursued. Significance Statement Artificial light at night (ALAN) profoundly disturbs the natural cycles of light and darkness that plants rely on to leaf out. In this study, we provide direct observational evidence that ALAN, an increasing environmental factor as a result of urbanization, advanced the date of breaking leaf buds and delayed the coloring of leaves in the conterminous United States. In a warmer and brighter night future, breaking leaf buds will continue to shift earlier, but the coloring of leaves will show a more complex response. The findings imply significant but under-appreciated consequences of ALAN on terrestrial ecosystems, which requires an interdisciplinary approach to investigate.
... The lives of moths (order Lepidoptera) are obscure for most people owing to their nocturnal lifestyles. Most of our encounters with these insects are limited to their erratic fluttering flights around our light bulbs at night [1], and enthusiasts and biologists attempt to understand their behaviour and diversity using moth light traps and illuminated sheets [2]. There are hundreds of thousands of species of moths-10-fold the number of butterfly species [3][4][5]-and include infamous agricultural pest species such as army worms [6], corn-and sugarcane borers [7] and cutworms [8], all of which are pests with an enormous potential to inflict severe economic damage [9]. ...
Article
Full-text available
There are hundreds of thousands of moth species with crucial ecological roles that are often obscured by their nocturnal lifestyles. The pigmentation and appearance of moths are dominated by cryptic diffuse shades of brown. In this study, 82 specimens representing 26 moth species were analysed using infrared polarimetric hyperspectral imaging in the range of 0.95–2.5 µm. Contrary to previous studies, we demonstrate that since infrared light does not resolve the surface roughness, wings appear glossy and specular at longer wavelengths. Such properties provide unique reflectance spectra between species. The reflectance of the majority of our species could be explained by comprehensive models, and a complete parametrization of the spectral, polarimetric and angular optical properties was reduced to just 11 parameters with physical units. These parameters are complementary and, compared with the within-species variation, were significantly distinct between species. Counterintuitively to the aperture-limited resolution criterion, we could deduce microscopic features along the surface from their infrared properties. These features were confirmed by electron microscopy. Finally, we show how our findings could greatly enhance opportunities for remote identification of free-flying moth species, and we hypothesize that such flat specular wing targets could be expected to be sensed over considerable distances.
... Two emerging and diffuse anthropogenic stressors in freshwaters are closely linked to urbanization: light pollution in the form of artificial light at night (ALAN) (Hölker et al., 2010;Kyba et al., 2017) and the spread of chemical pollution such as antibiotics (Amos et al., 2014;Bengtsson-Palme and Larsson, 2015). Light pollution can affect organism and nutrient fluxes across ecosystem boundaries (Manfrin et al., 2017) and can change microbial community composition (Grubisic et al., 2017), favouring taxa that benefit from nocturnal light and potentially leading to altered carbon budgets (Hölker et al., 2015). ...
Article
Freshwater microbes play a crucial role in the global carbon cycle. Anthropogenic stressors that lead to changes in these microbial communities are likely to have profound consequences for freshwater ecosystems. Using field data from the coordinated sampling of 617 lakes, ponds, rivers, and streams by citizen scientists, we observed linkages between microbial community composition, light and chemical pollution, and greenhouse gas concentration. All sampled water bodies were net emitters of CO2, with higher concentrations in running waters, and increasing concentrations at higher latitudes. Light pollution occurred at 75% of sites, was higher in urban areas and along rivers, and had a measurable effect on the microbial alpha diversity. Genetic elements suggestive of chemical stress and antimicrobial resistances (IntI1, blaOX58) were found in 85% of sites, and were also more prevalent in urban streams and rivers. Light pollution and CO2 were significantly related to microbial community composition, with CO2 inversely related to microbial phototrophy. Results of synchronous nationwide sampling indicate that pollution-driven alterations to the freshwater microbiome lead to changes in CO2 production in natural waters and highlight the vulnerability of running waters to anthropogenic stressors.
... Light pollution created by errant artificial lighting has increased rapidly and globally in recent years [1,2]. Artificial light from man-made environments can alter natural light regimes in adjacent wildlife habitats and thus affect species that live there, i.e., cause ecological light pollution [3]. ...
Article
Full-text available
Light pollution caused by poorly directed artificial lighting has increased globally in recent years. Artificial lights visible along marine turtle nesting beaches can disrupt natural brightness cues used by hatchling turtles to orient correctly to the ocean for their offshore migrations. Natural barriers, such as tall dunes and dense vegetation, that block coastal and inland lights from the beach may reduce this disruption. However, coastal areas are often managed toward human values, including the trimming of vegetation to improve ocean views. We used viewshed models to determine how reducing the dune vegetation height (specifically that of seagrape, Cocoloba uvifera) might increase the amount of artificial light from upland buildings that reaches a marine turtle nesting beach in Southeast Florida. We incorporated three data sets (LiDAR data, turtle nest locations, and field surveys of artificial lights) into a geographic information system to create viewsheds of lighting from buildings across 21 vegetation profiles. In 2018, when most seagrape patches had been trimmed to <1.1 m tall, female loggerhead turtles nested in areas with potential for high light exposure based on a cumulative viewshed model. Viewshed models using random (iterative simulations) and nonrandom selections of buildings revealed that untrimmed seagrape heights (mean = 3.1 m) and especially taller vegetation profiles effectively reduced potential lighting exposure from three building heights (upper story, midstory, and ground level). Even the tallest modeled vegetation, however, would fail to block lights from the upper stories of some tall buildings. Results from this study can support management decisions regarding the trimming of beach dune vegetation, any associated changes in the visibility of artificial lighting from the nesting areas, and modifications to existing lighting needed to mitigate light exposure.
... [10][11][12][13][14][15] During the past few decades, the global proportion of land area exposed to ALAN has increased drastically owing to rapid urbanization. It is estimated that outdoor ALAN increased by 5% to 20% annually in many urban places, 16 and more than four-fifths of the global population is now affected by nocturnal light pollution. 17 Previous epidemiological studies in adults suggest that the rapid growth of outdoor ALAN may be associated with a higher risk of poor sleep health. ...
Article
Full-text available
Importance: Healthy sleep has an important role in the physical and mental health of children. However, few studies have investigated the association between outdoor artificial light at night (ALAN) and sleep disorders in children. Objective: To explore the associations between outdoor ALAN exposure and sleep disorders in children. Design, setting, and participants: This population-based cross-sectional study, part of the National Chinese Children Health Study, was conducted from April 1, 2012, to June 30, 2013, in the first stage and from May 1, 2016, to May 31, 2018, in the second stage in 55 districts of 14 cities in China. This analysis included 201 994 children and adolescents aged 2 to 18 years. Data were analyzed from February 20 to March 21, 2022. Exposures: Outdoor ALAN exposure (in nanowatts per centimeters squared per steradian) within 500 m of each participant's residential address obtained from the satellite imagery data, with a resolution of approximately 500 m. Main outcomes and measures: Sleep disorders were measured by the Chinese version of the Sleep Disturbance Scale for Children. Generalized linear mixed models were used to estimate the associations of outdoor ALAN with sleep scores and sleep disorders. Results: The study included 201 994 children and adolescents (mean [SD] age, 11.3 [3.2] years; 106 378 boys [52.7%]), 7166 (3.5%) of whom had sleep disorder symptoms. Outdoor ALAN exposure of study participants ranged from 0.02 to 113.48 nW/cm2/sr. Compared with the lowest quintile (Q1) of outdoor ALAN exposure, higher quintiles of exposure (Q2-Q5) were associated with an increase in total sleep scores of 0.81 (95% CI, 0.66-0.96) in Q2, 0.83 (95% CI, 0.68-0.97) in Q3, 0.62 (95% CI, 0.46-0.77) in Q4, and 0.53 (95% CI, 0.36-0.70) in Q5. Higher quintiles of exposure were also associated with odds ratios for sleep disorder of 1.34 (95% CI, 1.23-1.45) in Q2, 1.43 (95% CI, 1.32-1.55) in Q3, 1.31 (95% CI, 1.21-1.43) in Q4, and 1.25 (95% CI, 1.14-1.38) in Q5. Similar associations were observed for sleep disorder subtypes. In addition, greater effect estimates were found among children younger than 12 years. Conclusions and relevance: The findings of this cross-sectional study suggest that sleep disorders are more prevalent among children residing in areas with high levels of outdoor ALAN and the associations are generally stronger in children younger than 12 years. These findings further suggest that effective control of outdoor ALAN may be an important measure for improving the quality of children's sleep.
... Artificial light at night (hereafter, ALAN) has brought benefits to humans and was first perceived as a technological advancement that would increase the comfort and wellbeing of modern civilizations. However, it is now increasingly accepted by the scientific community that it also results in damaging effects to living organisms, including humans, and is an ever-increasing global pollutant that threatens biodiversity at multiple scales (Hölker et al., 2010;Swaddle et al., 2015;see below). Because ALAN reaches not only areas close to its sources, but also far away sites through sky-glow, it can have far-reaching impacts on organisms and ecosystems. ...
Article
Full-text available
The growing global population has increased the demands for urban housing development not only in the cities but in suburbs and rural areas as well. This gradual but speedy urbanization and globalization have introduced a new kind of “night lifestyle” among people, who engage in various entertainment activities late in the evening till early mornings. This influx of urban architecture and changes in lifestyles have resulted in increased use of various kinds of lighting systems in our cities to a point where some cities like Mumbai and New York City are known as “the cities that never sleep.” Although this might be contributing significantly to the economy, they cause greater harm-light pollution, with little to no awareness. This paper, therefore, deals with the various types and causes, and thus the consequences of light pollution, ranging from plants, animals, humans to astronomy. The documentation done so far concerning light pollution has been done by scientists and astronomers from the West. Thus, an attempt has been made to assess the awareness ratio among Indians between the ages of 16–65 through an online questionnaire, analyzing the collected data qualitatively. It was found that majority of the participants were not aware about the term ‘light pollution’ and consequently were not aware about the threat that comes with it. So the objective of this review paper is to bring attention to the severity of the issue of light pollution and make people aware of the consequences it has on our lives. All the effective mitigation policies and regulations from various countries around the world that were theorized to deal with this risk and propagate awareness are included. Our goal is to bring these solutions to practice in the Asian and South Asian countries like India and make the masses informed as light pollution is still a relatively new and alien concept.
Preprint
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Luz Artificial Nocturna (ALAN) es un problema para el estudio del Universo y puede generar efectos adversos en la biodiversidad y la salud humana. Dado que se prevé que las emisiones globales de ALAN aumenten en 6% cada año. Las actividades urbanas y portuarias próximas al humedal río Maipo y lagunas adyacentes, sugieren una amenaza en el sector, por lo que se postula que existirán especies sensibles a la contaminación lumínica expuestas a niveles de calidad de cielo similar al área urbana aledaña. Para comprobar lo anterior se procedió a evaluar la susceptibilidad que los vertebrados existentes la desembocadura del río Maipo pueden manifestar a ALAN. Se categorizó el tipo de cielo existente en distintos puntos de un transecto utilizando un medidor de calidad de cielo (SQM-L) y se buscó información de las especies de vertebrados sensibles a ALAN. Los resultados señalan que todos los puntos muestreados presentan promedios de calidad de sectores urbanos (según la escala de Bortle); donde 23.35% de las 137 especies de vertebrados presentes en el humedal ha demostrado efectos de ALAN. Por lo anterior, es importante considerar medidas que eviten una mayor degradación del lugar el cual está en un área de importancia internacional por su biodiversidad. Palabras Claves: ALAN, Contaminación lumínica, Humedales, SQM
Article
During six consecutive autumn seasons we registered birds that were attracted to an illuminated 41-storey building in Bonn, Germany, the so-called ‘Post Tower’. Casualties on the ground were disoriented by the light and in most cases collided with the building. All-night observations with numbers of casualties, effective light sources, moon, and weather parameters registered hourly allowed for analyses of the role of these factors for the attraction and disorientation of numerous migratory birds. As expected, the conspicuous façade illumination was responsible for many casualties (fatal or non-fatal). Additionally, the illuminated roof logos and even faint light sources like the emergency lights were attractive and led to casualties. Moon and rain were negatively correlated with casualties, but there was no clear correlation with other weather parameters. Turning off lights was key, but effects of other ex post mitigation measures were limited: shutters were not originally intended for the attenuation of light emissions, control technology was insufficient, and there was a lack of willingness of the building owner to reduce light emissions consistently, even during core bird migration periods. Conservation recommendations are derived from this case study.
Article
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This paper presents an analysis of the optical night sky brightness and extinction coefficient measurements in UBVRI at the Indian Astronomical Observatory (IAO), Hanle, during the period 2000-2008. They are obtained from an analysis of CCD images acquired at the 2 m Himalayan Chandra Telescope (HCT) at IAO. Night sky brightness was estimated using 210 HFOSC images obtained on 47 nights and covering the declining phase of solar activity cycle-23. The zenith corrected values of the moonless night sky brightness in mag arcsec^-2 are 22.14 ± 0.32 (U), 22.42 ± 0.30 (B), 21.28 ± 0.20 (V), 20.54 ± 0.37 (R) and 18.86 ± 0.35 (I) band. This shows that IAO is a dark site for optical observations. No clear dependency of sky brightness with solar activity (implied by the 10.7 cm solar flux) is found. Extinction values at IAO are derived from an analysis of 1325 images over 58 nights. They are found to be 0.36 ± 0.07 in U-band, 0.21 ± 0.04 in B-band, 0.12 ± 0.04 in V-band, 0.09 ± 0.04 in R-band and 0.05 ± 0.03 in I-band. On an average, extinction during the summer months is slightly larger than that during the winter months. This might be due to an increase of dust in the atmosphere during the summer months. No clear evidence for a correlation between extinction in all bands and the average night time wind speed is found. Also, presented here, is the low resolution moonless optical night sky spectrum for IAO covering the wavelength range 3000 - 9300 Å. Features from O, OH, N and Na are seen in the spectra. Hanle, thus has the required characteristics of a good astronomical site in terms of night sky brightness and extinction, and could be a natural candidate site for any future large aperture Indian optical-infrared telescope(s).
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Nightsat is a concept for a satellite system capable of global observation of the location, extent and brightness of night‐time lights at a spatial resolution suitable for the delineation of primary features within human settlements. Based on requirements from several fields of scientific inquiry, Nightsat should be capable of producing a complete cloud‐free global map of lights on an annual basis. We have used a combination of high‐resolution field spectra of outdoor lighting, moderate resolution colour photography of cities at night from the International Space Station, and high‐resolution airborne camera imagery acquired at night to define a range of spatial, spectral, and detection limit options for a future Nightsat mission. The primary findings of our study are that Nightsat should collect data from a near‐synchronous orbit in the early evening with 50 to 100 m spatial resolution and have detection limits of 2.5E Watts cmsrµm or better. Although panchromatic low‐light imaging data would be useful, multispectral low‐light imaging data would provide valuable information on the type or character of lighting; potentially stronger predictors of variables such as ambient population density and economic activity; and valuable information to predict response of other species to artificial night lighting. The Nightsat mission concept is unique in its focus on observing a human activity, in contrast to traditional Earth observing systems that focus on natural systems.
Article
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Recent (1998-1999) broadband photometry of the night sky brightness at Mount Wilson Observatory is compared to similar data recorded in 1973 and with measurements from other astronomical observatories. These measurements show the observatory's B- and V-band night sky brightness have increased by 0 · 8 and 1 · 0 mag. arcsec 2 over the last three decades, respectively. However, the I-band sky brightness of 18-8 mag. arcsec -2 compares favourably with other observatories known for their dark night skies. These results emphasize the importance of protecting the night sky brightness, while demonstrating that even under bright optical skies there are opportunities to continue to observe at longer wavelengths.
Article
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Before the mid-eighteenth century, most people lived in near-complete darkness except in the presence of sunlight and moonlight. Since then, the provision of artificial light has been revolutionised by a series of innovations in appliances, fuels, infrastructures and institutions that have enabled the growing demands of economic development for artificial light to be met at dramatically lower costs: by the year 2000, while United Kingdom GDP per capita was 15 times its 1800 value, lighting services cost less than one three thousandth of their 1800 value, per capita use was 6,500 times greater and total lighting consumption was 25,000 times higher than in 1800. The economic history of light shows how focussing on developments in energy service provision rather than simply on energy use and prices can reveal the ÔtrueÕ declines in costs, enhanced levels of consumption and welfare gains that have been achieved. While emphasising the value of past experience, the paper also warns against the dangers of over-reliance on past trends for the long-run forecasting of energy consumption given the potential for the introduction of new technologies and fuels, and for rebound and saturation effects.
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We present optical (UBVRI) sky brightness measurements from 1992 through 2006. The data are based on CCD imagery obtained with the CTIO 0.9, 1.3, and 1.5 m telescopes. The B- and V-band data are in reasonable agreement with measurements previously made at Mauna Kea, although on the basis of a small number of images per year, there are discrepancies for the years 1992 through 1994. Our CCD-based data are not significantly different than values obtained at Cerro Paranal. We find that the yearly averages of V-band sky brightness are best correlated with the 10.7 cm solar flux taken 5 days prior to the sky brightness measurements. This implies an average speed of 350 km s -1 for the solar wind. While we can measure an enhancement of the night-sky levels over La Serena 10° above the horizon, at elevation angles above 45°, we find no evidence that the night-sky brightness at Cerro Tololo is affected by artificial light of nearby towns and cities. © 2007. The Astronomical Society of the Pacific. All rights reserved.
Article
Recent (1998-1999) absolute spectrophotometry of the night sky over two southern Arizona astronomical sites, Kitt Peak and Mount Hopkins, is compared to similar data obtained in 1988 at each site. The current zenith sky brightness in the range ~3700-6700 Å is essentially identical at the two sites and is as dark now as Palomar Observatory was in the early 1970s, when it was generally considered a premier dark observing site. Converted to broadband measurements, our spectrophotometry is equivalent to B=22.63, V=21.45 mag arcsec-2, for the zenith night sky. The contribution of high-pressure sodium street lights to broadband V is about 0.2 mag arcsec-2, comparable to the strong airglow O I lambda5577 line. During the period from 1988 to 1998-1999, the zenith sky brightness increased only modestly, with the largest changes being seen for Kitt Peak, where the zenith sky has brightened by ~0.1-0.2 mag arcsec-2 in the blue-optical region. For Kitt Peak we also have both 1988 and 1999 observations at modestly large zenith distances (ZD~60deg). In the directions away from Tucson, the sky has brightened by ~0.35 mag arcsec-2 over the intervening decade. Toward Tucson the change has been larger, approximately 0.5 mag arcsec-2. In most directions the increase in the sky brightness has lagged behind the fractional increase in population growth, which we attribute to good outdoor lighting ordinances, a fact which is further reflected in the decrease in Hg emission. However, our results emphasize the need for diligent attention as developments creep closer to our observing sites. The research described here is based on data obtained in part at the MMT Observatory, a joint facility of the Smithsonian Institution and the University of Arizona.
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There have been major qualitative and quantitative changes in outdoor lighting technology in the last decade. The level of skylight caused by outdoor lighting systems is growing at a very high rate, about 20 percent per year nationwide. In addition, the spectral distribution of man-made light pollution may change in the next decade from one containing a few mercury lines to one containing dozens of lines and a significantly increased continuum level. Light pollution is presently damaging to some astronomical programs, and it is likely to become a major factor limiting progress in the next decade. Suitable sites in the United States for new dark sky observing facilities are very difficult to find. Some of the increase in outdoor illumination is due to the character of national growth and development. Some is due to promotional campaigns, in which questionable arguments involving public safety are presented. There are protective measures which might be adopted by the government; these would significantly aid observational astronomy, without compromising the legitimate outdoor lighting needs of society. Observatories should establish programs to routinely monitor sky brightness as a function of position, wavelength, and time. The astronomical community should establish a mechanism by which such programs can be supported and coordinated.
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The present and future effect of artificial illumination on ground-based optical astronomical observations in California and Arizona is discussed. It is concluded that the effectiveness of all major observatories in these states is presently or potentially limited by light pollution. Consequently, it is essential that immediate efforts be undertaken to: (1) Control outdoor illumination to lengthen the useful life of existing observatory sites, and (2) Identify and protect the best remaining sites both within and outside the United States. The characteristics and probable locations of the best sites for ground-based optical astronomical observations are discussed.
Article
The brightness of the night sky at the Mount Wilson Observatory has been calculated for the years from 1900 to 2000. Data on street lighting in Los Angeles City and estimates for light from residences, shops, and businesses have been used to calculate the per capita light-emission rates. These have been used in model brightness calculations with the populations of many cities in the Los Angeles Basin. The results show the relentless increase in night-sky brightness that is continuing at this time.
Article
The recognition that the elements of the ‘anthropocene’ play a critical role in global change processes means that datasets describing elements of the socio-economic environment are becoming increasingly more desirable. The ability to present these data in a gridded format as opposed to the traditionally reported administrative units is advantageous for incorporation with other environmental datasets. Night-time light remote sensing data has been shown to correlate with national-level figures of Gross Domestic Product (GDP). Night-time radiance data is analysed here along with regional economic productivity data for 11 European Union countries along with the United States at a number of sub-national levels. Night-time light imagery was found to correlate with Gross Regional Product (GRP) across a range of spatial scales. Maps of economic activity at 5 km resolution were produced based on the derived relationships. To produce these maps, certain areas had to be excluded due to their anomalously high levels of economic activity for the amount of total radiance present. These areas were treated separately from other areas in the map. These results provide the first detailed examination of night-time light characteristics with respect to local economic activity and highlight issues, which should be considered when undertaking such analysis.