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The introduction and widespread uptake of LEDs as outdoor lighting has caused no small amount of concern amongst conservation biologists. The prevailing impression that LEDs are always blue-white is well founded as adoption of LEDs for streetlights were invariably high color temperatures and with the deterioration of phosphors the blue wavelengths penetrated even more. But LEDs do have characteristics that differentiate them from other light sources and may allow for the reduction of environmental effects of lighting on species and habitats: direction, duration, intensity, and spectrum. Travis Longcore, Assistant Professor at the University of Southern California’s School of Architecture, sheds light on all these aspects.
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Issue 70 | © 2018 Luger Research e.U.
Hazard or Hope?
LEDs and Wildlife
The introduction and widespread uptake of LEDs as outdoor lighting has caused no small amount of
concern amongst conservation biologists. The prevailing impression that LEDs are always blue-white
is well founded as adoption of LEDs for streetlights were invariably high color temperatures and with
the deterioration of phosphors the blue wavelengths penetrated even more. But LEDs do have
characteristics that dierentiate them from other light sources and may allow for the reduction of
environmental eects of lighting on species and habitats: direction, duration, intensity, and spectrum.
Travis Longcore, Assistant Professor at the University of Southern California’s School of Architecture,
sheds light on all these aspects.
Outdoor lighting sources that
have been in use for the better
part of a century or more are
rapidly being phased out in
favor of LEDs. The industry
has delivered consistent
improvements in efficiency
extending across a wide
spectral range and with control
capabilities unimaginable
to previous generations of
lighting designers. Yet, the
introduction and widespread
uptake of LEDs as outdoor
lighting has caused no small
amount of concern amongst
conservation biologists. Leading
bat researchers wondered if
LEDs were “conserving energy
at the cost of biodiversity” [1].
Another group investigating
insects declared “LED lighting
increases the ecological
impact of light pollution” [2].
A horizon scan of threats to
urban ecosystems listed LEDs
and the associated profusion
of bright white light [3]. Most of
these concerns, however, are
based on the experience of the
general public that LEDs used
in outdoor lighting can only
be blue-white - or on studies
of instances where the switch
to LEDs is in fact to high color
temperature whites [4,5].
The prevailing impression
that LEDs are always blue-
white is well-founded. Early
adoption of LEDs for streetlights
was invariably high color
temperatures as a result of
their higher efficiency during
that phase of technological
development. As these
products aged and the
phosphors deteriorated, the
blue wavelengths penetrated
even more. It is no surprise
that the public, and wildlife
researchers included, perceived
high color temperatures to be
an inherent attribute of LEDs.
This misconception continues
today, even though a wider
range of spectral configurations
of LEDs are competitive and
installed across the world.
It seems possible, as well, that
LED professionals are unfamiliar
with the concerns about the
effects of outdoor lighting
that motivate conservation
biologists to regard LEDs with
suspicion. The purpose of this
essay is to reconcile these
two realms by addressing the
question of whether LEDs
pose a risk or opportunity to
wildlife conservation. LEDs
do have characteristics that
differentiate them from other
light sources. The influence of
these characteristics fall into the
four major attributes that have
been identified as important to
reducing environmental effects
of lighting on species and
habitats: direction, duration,
intensity, and spectrum [6].
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LIGHT SPECTRUM & WILDLIFE
© 2018 Luger Research e.U. | Issue 70
53
Direction
LEDs as currently deployed in street
lighting tend to be quite directional,
casting most light on the ground
and little light at the horizontal or
higher. In this regard they can be an
improvement over other lamp types
that have drop lenses resulting in
more light scattering to locations
where it is not useful. With the use
of microlens arrays, the focus of
LED streetlights on the street and
adjacent pedestrian zones could be
nearly perfect [7]. So long as lights
are not pointing downward into a
sensitive habitat (e.g., a wetland [8]),
the directionality of LED streetlights
can be an improvement in terms of
wildlife impacts. Bulb-type LED
lamps, however, offer no such
benefit and their deployment in
unshielded fixtures presents the
same challenges as previous
technologies.
Duration
One of the most effective ways to
reduce the unintended adverse
effects of lighting is to turn lights off
when they are not needed. For most
lamp types previously used for
municipal outdoor lighting, turning
the lamp on and off comes with an
energetic penalty or warmup period.
In contrast, LEDs can easily be
extinguished and illuminated without
delay. Consequently, LEDs are
suited to the use of controls that use
either timing or motion/heat
detection to extinguish lights when
they are not needed.
Intensity
Intensity of light is easily controlled
in LEDs, they are dimmable without
difficulty. So from the perspective of
reducing lighting levels to the
minimum needed for required tasks,
they are ideal. Yet, the tendency is
for designers and end users to use
more light with LEDs because they
are so energy efficient [9]. This
phenomenon is well-known in
environmental economics, known as
the “rebound effect” [10]. It seems
that users find that it is preferable to
use a brighter bulb when the energy
savings are great. LEDs represent
an era of cheap light and when a
product is inexpensive, the tendency
is to overconsume. Just as cheap
(fast) food has resulted in an obesity
epidemic in the United States and
elsewhere [11], cheap light has the
potential to result in unnecessarily
bright nights.
Spectrum
The flexibility of LEDs when it comes
to spectrum, contrasts dramatically
with the perception that LEDs used
for outdoor lighting are intrinsically
bluish white. Rather, the rapid
development of a range of spectral
combinations offers many possible
options that could be exploited to
reduce impacts on wildlife and the
environment.
Insect attraction to LEDs is lower
across the board when compared
with lamps that emit ultraviolet light.
Both “warm” and “cold” LEDs have
been compared with metal halide
and mercury vapor lamps and found
to attract less than a tenth of the
number of insects, a finding that is
attributable to the difference in
ultraviolet emissions [12]. Conversely,
most broad spectrum LEDs used in
outdoor lighting do have a potential
to adversely impact the perception
of daylength (and thus seasonality)
Figure 1:
A hatchling logger head
sea turtle c rawls
towar d a high -pres sure
sodium luminaire on
the F lorida coas t
(Photo Credits:
Blair Witherington)
LIGHT SPECTRUM & WILDLIFE
RESEARCH
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Issue 70 | © 2018 Luger Research e.U.
in plants, because the peak sensitivity
of the phytochromes that detect
daylength are in range of LED peak
emissions for most full-spectrum LEDs.
Beyond these two examples, the
combination of tunable LEDs, filters
combined with LEDs, and colored
LEDs such as PC Amber offer
unique opportunities. Spectrum can
be controlled by combining different
colored diodes in many
configurations (red, blue, green, and
perhaps also white, amber with
white). The number of combinations
far outstrips previous technologies,
where the spectral output of high
pressure sodium, low pressure
sodium, metal halide, xenon,
fluorescent, and incandescent
lamps were well-known and
inflexible.
Choosing Spectrum to
Reduce Wildlife Disruption
To take advantage of the range of
possibilities from LEDs, the quantal
flux at dif ferent wavelengths can be
compared with the behavioral
responses of wildlife across those
wavelengths. A generalized
response curve for all insects was
just published [13] and curves exist
for other species [14]. The
intersection of the response curves
with the spectral power distribution
of the lamps (converted to photons)
can be compared with the same
calculations for an equal lux of a
standard illuminant to provide a
comparison of the effects of
different light sources [14].
Response curves for insects
(averaging three curves in the
literature), sea turtle (averaging three
curves in the literature), juvenile
salmon, and a visual response curve
for the endangered seabird Newell’s
Shearwater were used to construct
a composite metric of wildlife
impacts and compared with a range
of lamp types and standard
illuminants. Plotting the results
relative to Correlated Color
Temperature (CCT) reveals two
characteristics of the impacts of
lights (Figure 2). First, on average
and for each species or group,
lower CCTs had lower predicted
effects. Second, the slope of the
relationship between CCT and
wildlife influence was greater for
some groups than others, indicating
that spectrum could be a more
effective tool to reduce impacts on
insects and juvenile salmon than on
Newell’s Shearwater.
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Figure 2 :
Relation ship of
modeled effect of
lamps on dif fe rent
wildlife speci es o r
groups ( juven il e
salmon , Newell’s
shearwater,
sea turtles, inse cts,
and their ave rage)
with Correlated Color
Temp erature ( CCT )
of th e la mps.
Data from [14]
Figure 3 :
Relationship of
cor related color
temperature to average
wildlife sensitivit y with
lamps and illuminants
labelled. Data from [14]
LIGHT SPECTRUM & WILDLIFE
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© 2018 Luger Research e.U. | Issue 70
Figure 4:
Rank ing of light ing
source s th at e qually
weighs wildlife
respon se, melanop ic
respon se, astro nomical
light pollution (Star
Light Index [15]), a nd
Color Rendering Index.
Reprin te d fr om [ 14].
Shor ter bar s re prese nt
a combinatio n of lowe r
wildlife responses and
higher CRI
CCT is not a perfect predictor of
effects on wildlife, but it is a
reasonable rule of thumb that lower
CCT will be less disruptive to wildlife
(and we already know that it will be
less disruptive for circadian rhythms
and astronomical observation [15]).
The lamps with the lowest projected
influence on wildlife overall were
low-pressure sodium (which is being
phased out), high-pressure sodium,
PC amber LEDs, and filtered LEDs
(Figure 3).
Figure 3: Thus far, the results
represent the predicted effects of
the lamps on wildlife. To account for
preferences in outdoor lighting,
another ranking was created that
incorporated a penalty for low color
rendering index (CRI). Any lamp with
a CRI over 75 was assumed to have
adequate color rendering, while
those with lower CRI were penalized
in the overall index. The resulting
ranking of lamps is notable in that
low pressure sodium ranks lower
because of its extremely low CRI,
while PC Amber and filtered LEDs
rank the highest, balancing both
lower wildlife impacts with
reasonable if not high CRIs (Figure
4).
As a rule of thumb, CCT can be
used as an indicator of wildlife
effects, but this may not hold true
across all applications. Migrating
birds cannot orient under red light
and therefore solid red lights are to
be avoided on communication
towers [16]. Green light has support
for minimizing attraction of nocturnal
migrant birds [17]. Other special
cases exist and would require
consultation with experts on a
particular taxonomic group or
species at risk.
Tuning Within the
Same CCT
An additional useful feature of LED
lamps is that they can be configured
to produce the same CCT with
different spectral outputs. To
demonstrate this approach to
minimize insect attraction, the
spectral response curves for bees
and moths were used to choose
between configurations of two 2700
K LEDs (produced with a prototype
tunable lamp with RGB diodes) and
one 3000 K LED in a manner
predicted to reduce insect
attraction. The custom
configurations were then compared
in a field study with an off-the-shelf
2700 K LED and 2700 K fluorescent
lamp [18].
The results of this field experiment
showed that a tunable LED attracted
20-21% fewer insects than a similar
LED not designed with minimizing
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RESEARCH
insect attraction as an objective
(Figure 5). This effect was large for
moths, similar to the findings when
comparing different CCT lamps.
These results are especially
important for the choice of indoor
lighting in the tropics, where glass
and screens on windows is not
common. Using indoor light that
provides adequate color rendering
for work while reducing insect
attraction would reduce the
probability of exposure to
phototactic insect vectors of disease
[18]. LEDs offer this possibility
because of the spectral flexibility in
their design.
Certainly, conservation scientists
have more work to do on spectral
responses. The number of species
response curves available needs to
be increased, which requires
experts across taxonomic groups to
engage the topic. The relationship
between light intensity and spectral
responses is largely unknown and
needs research across nearly all
wildlife groups. Even the perception
of light by different groups of wildlife
species is not fully described and
taxonomic-specific metrics of both
radiance and irradiance are needed.
Nevertheless, a “no regrets”
approach can be taken to guide the
choice of spectrum that LEDs make
possible, which is to reduce blue
content. With amber and filtered
products on the market, low color
temperatures 2200 K are feasible
and desirable to minimize adverse
impacts.
Conclusions
The efficiency benefits of LEDs and
the resulting economic incentives
will drive further conversion of
outdoor and indoor lighting to the
technology. If the tendency to light
more when light is cheaper can be
overcome, the other attributes of
LEDs hold significant promise for
reducing environmental effects.
Realizing that promise requires
designers and manufacturers to
learn about and embrace the
guidance that wildlife scientists can
provide. In some instances it will be
challenging - resisting the desire to
up-light, using no more light than
necessary, and educating clients on
the benefits of spectral choices that
do not look like daylight. In other
contexts, environmental regulations
are likely to dictate lighting choices
and offer an opportunity if the
industry is prepared to seize it. On
each of the mitigation approaches
- duration, direction, intensity, and
spectrum - LEDs will inherently or
can be designed to perform well.
Whether they do in practice will be
up to the LED professional.
Figure s 5:
Compar ison of
attr actio n of insec ts,
and subset s of flies
(Dipter a), m ot hs
(Lepidopter a ), and
other insects to 2700
K compact fluorescent
(C FL ), custom 3000 K
LED ( A ), off-the-shelf
270 0K LED, two custom
270 0 K LEDs ( B and
C), and a co ntrol ( NO).
Average c atch p er n ight
with 95% confide nce
intervals (se e [18 ] for
details)
LIGHT SPECTRUM & WILDLIFE
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© 2018 Luger Research e.U. | Issue 70
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LIGHT SPECTRUM & WILDLIFE
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... In particular, lamp color and directionality are two key streetlight features that can affect fallout [7,16]. Spurred by efforts to improve energetic efficiency, many cities are replacing yellow high-pressure sodium (HPS) lightbulbs commonly used in streetlights with white light-emitting diode (LED) bulbs [17][18][19]. Although LED bulbs decrease electricity consumption and maintenance costs, these benefits could be costly to wildlife, as shearwaters may be more sensitive to LED lights [7]. ...
... This approach, when applied to HPS lights, reduced Newell's Shearwater (Puffinus newelli) fallout on Kauai (Hawai'i) [16]. Although mitigation is being addressed through shielding, the common use of optimized LEDs with broad spectra and Correlated Color Temperature (CCT) greater than the maximum recommended value for wildlife (2200 K) may be a cause for concern [17]. While modern LED lights possess the flexibility to give off a range of low to high CTT, short-wavelength light with high CCT is a common choice because of its efficiency [19]. ...
... A recent survey of lighting experts suggests that while LEDs can be adjusted to reduce light pollution and minimize wildlife impacts, yet municipalities rarely capitalize on those benefits [19]. For instance, although new-technology LED streetlights can filter out lower wavelengths [17], full spectrum white LED lights maximize brightness, and are commonly chosen to replace HPS streetlights. Furthermore, LEDs come in a variety of CCTs with options as low as 2200 K, the maximum temperature experts recommend for wildlife [17]. ...
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This thought-provoking but accessible book critically examines the dominant food regime on its own terms, by seriously asking whether we can afford cheap food and by exploring what exactly cheap food affords us. Detailing the numerous ways that our understanding of food has narrowed, such as its price per ounce, combination of nutrients, yield per acre, or calories, the book argues for a more contextual view of food when debating its affordability. The first edition, published in 2011, was widely praised for its innovative approach and readability. In this new edition the author brings all data and citations fully up to date. Increased coverage is given to many topics including climate change, aquaculture, financialization, BRICS countries, food-based social movements, gender and ethnic issues, critical public health and land succession. There is also greater discussion about successful cases of social change throughout all chapters, by including new text boxes that emphasize these more positive messages. The author shows why today's global food system produces just the opposite of what it promises. The food produced under this regime is in fact exceedingly expensive. Many of these costs will be paid for in other ways or by future generations and cheap food today may mean expensive food tomorrow. By systematically assessing these costs the book delves into issues related, but not limited, to international development, national security, healthcare, industrial meat production, organic farming, corporate responsibility, government subsidies, food aid and global commodity markets. It is shown that exploding the myth of cheap food requires we have at our disposal a host of practices and policies.
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In the summer of 2008 the City of Düsseldorf and that city's Agenda 21 group initiated a study to evaluate insect flight activity to street lights. We compared modern lamp types such as metal halide and LEDs to older lamp types, e. g. high pressure mercury lamps, high pressure sodium lamps and fluorescent lamps. Traps were exposed in a daily pattern. We analysed 964 nightly samples containing 33,896 insects belonging to 13 insect orders, of which 7 predominated while 6 were counted only in lower numbers. To compare flight activity we used attraction to the high pressure mercury lamps as reference (= 100 %). On this basis we found a sequence of attraction for all insect orders together down to -80 %. The 7 most common orders behaved very differently, e. g. the moths were attracted to minimum values in the range of -95 %. Two orders were found to be attracted stronger than the reference. The most significant differences for most insects were between LEDs and all the other lamp types. LEDs do not emit any UV and appear to be very insect friendly. However, we need more studies to conclusively evaluate these results. As a final point, the very low activity of nocturnal insects around street lamps in the Fleher Deich area of Düsseldorf must be regarded as an indication of an impoverished insect fauna overall.
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As urbanization intensifies, urban ecosystems are increasingly under pressure from a range of threats. Horizon scanning has the potential to act as an early warning system, thereby initiating prompt discussion and decision making about threat mitigation. We undertook a systematic horizon scanning exercise, using a modified Delphi technique and experts from wide-ranging disciplines, to identify emerging threats in urban ecosystems. The 10 identified threats were generally associated with rapid advances in technology (eg solar panels, light-emitting diode lights, self-healing concrete) or with societal demands on urban nature (eg green prescriptions). Although many of the issues identified are also technological opportunities with recognized environmental benefits, we have highlighted emerging risks so that research and mitigation strategies can be initiated promptly. Given the accelerated rate of technological advancement and the increasing demands of urbanized populations, horizon scanning should be conducted routinely for urban ecosystems. Read More: http://www.esajournals.org/doi/10.1890/150229
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