Reporter Stephanie Pain contributed an excellent summary of recent research on light pollution, “There Goes the Night,” with interviews and summaries of research from around the world. Knowable Magazine is the partner publication to the Annual Reviews series, which recently published a review from the Gaston lab, Impacts of Artificial Light at Night on Biological Timings. Our favorite part, however, is that the article included an image from Ben Banet, who graduates this spring with an interdisciplinary B.S. in conservation and GIS that focused on light pollution. His image of the Smithsonian research hut on Mt. Whitney with the glow of Los Angeles on the horizon 285 km in the distance provided a striking illustration for the article.
Author: Travis Longcore
Two light pollution research updates
I’m usually one to announce research results and not grant funding, but the funders put out a release and Tweet, so it is officially news that we are starting a new 2-year project: Coast Light: Actionable Science to Manage Coastal Nightscapes. The funding is from USC Sea Grant and includes in-kind contributions from many partners that will make the project possible — including data, labor, and/or time from Los Angeles County Museum of Natural History (collaborating on measuring influence of light on settlement rates of marine invertebrates), The Aerospace Corporation (providing coastal night light measurements by cubesat!), Los Angeles Audubon Society and the many volunteer snowy plover monitors, and Professor Karen Martin at Pepperdine (grunion data). More about the project as it develops — I’ll be co-advising a Ph.D. student from Biological Sciences who will be the official Sea Grant Trainee on the project.
Preliminary results from analysis of radiance-weighted nighttime boat detections by month off the coast of southern California (Gutierrez-Dewar, Elvidge, and Longcore, unpublished data).
Our Park Light research efforts are coming to an interim head, as at least three lab members will present at the Los Angeles Geospatial Summit on February 23. Harrison Knapp and Ben Banet will present a classification of National Park Service units based on the lighting conditions inside the parks and in buffers surrounding them, so that parks can know what other parks face similar issues for light pollution management. Eliza Gutierrez-Dewar has some very interesting results looking at the spatial and temporal distribution of squid boats off the Pacific Coast, which can be identified using night lights because of the bright lights used by squid fishers to attract the squid up near the surface where they can be caught. This project builds on data produced by an automated boat detection algorithm developed by Chris Elvidge’s group at NOAA and is of significant interest to land managers looking to protect sensitive seabird nesting sites from excessive light (and associated predation risk) during nesting season. We may have another poster, but I have not reviewed the final program yet.
Urban (de)greening research in USCDornsife Magazine
The fall edition of USCDornsife Magazine is out and includes a numerical summary of our research on mansionization and urban forest cover in Los Angeles single-family neighborhoods. Although not mentioned, Catherine Rich and John P. Wilson were co-authors of the paper, published in Urban Forestry and Urban Greening earlier this year.
Drivers of plant community structure on San Clemente Island
A third paper from our collaboration with Scott Loss and post-doc Shishir Paudel at Oklahoma State University has been published in Ecosphere. This paper analyzes the vegetation data collected as Shishir searched for invasive earthworms on the island.
Determinants of native and non-native plant community structure on an oceanic island
Shishir Paudel, Juan C. Benavides, Beau MacDonald, Travis Longcore, Gail W. T. Wilson, and Scott R. Loss
Understanding the relative importance of environmental and anthropogenic factors in driving plant community structure, including relative dominance of native and non-native species, helps predict community responses to biological invasions. To assess factors influencing plant communities on San Clemente Island, USA, we conducted an islandwide vegetation survey in which we measured plant species richness and percent cover of native and non-native plants, as well as physical environmental variables, soil chemical properties, abundance of soil microbial functional groups (e.g., arbuscular mycorrhizal fungi [AMF]), and a human disturbance variable (distance to road). We found that total plant species richness decreased with increasing non-native plant cover, soil pH, and AMF abundance. Native plant cover increased with increasing distance to a major paved road and decreased with increasing soil moisture and pH. Non-native plant cover decreased with increasing distance to a major paved road and increased with increasing soil moisture, AMF abundance, and from southwest to northeast, a geographic/climatic gradient that represents increasing moisture. Nonmetric multidimensional scaling ordination further illustrated that trends in plant community composition were correlated with elevation, distance to a major paved road, and soil moisture, organic matter, and ammonium. These results suggest complex effects of physical environmental, soil chemical, and human-related factors on plant community structure on an oceanic island, and moreover, that different factors affect cover of native and non-native plants. Notably, our observation of apparent moisture limitation of non-native plants suggests that, in some contexts, drought conditions can limit plant invasions and may even represent an opportunity for efficient control or eradication of invasive plants. The apparent negative effect of non-native plants on native plant cover and overall plant species richness represents a conservation concern for native biodiversity on oceanic islands and suggests the potential for community reassembly as invasive species increasingly dominate due to anthropogenic disturbances.
, , , , , and . 2017. Determinants of native and non-native plant community structure on an oceanic island. Ecosphere 8(9):e01927. 10.1002/ecs2.1927
Forum on ecological certification for urban design
I’m pleased to have been asked to contribute to the most recent roundtable on the interdisciplinary blog, The Nature of Cities. Hop on over to join the discussion:
How bright the moon: correcting a propagated figure error in the literature
Last year, the National Park Service released our report, Artificial night lighting and protected lands: Ecological effects and management approaches (Longcore and Rich 2016), which had been in the works for quite a while. Our colleague Andrej Mohar, while enthusiastic about the report overall, pointed out that a figure that we had included of natural illumination under various conditions was wrong, and by quite a bit, when it came to the levels under a “quarter moon.” This is the story of that error, where it came from, and its correction.
The figure we used in the 2016 NPS report was re-printed with very minor adjustments from Paul Beier’s chapter in our 2006 edited book, Ecological Consequences of Artificial Night Lighting (Island Press).
This figure was published in Ecological Consequences of Artificial Night Lighting and re-published with slight adjustment of the icons in our 2016 NPS report.
The “quarter moon” is shown as causing ground-based illumination of 0.1 lux or thereabouts. This is obviously and very wrong, and in fact is contradicted in Chapter 1 of the book, which indicates 0.01-0.03 lux for a quarter moon. We should have caught it then, but did not.
Furthermore, a quarter moon, technically, is half of the disk of the moon illuminated, which is one quarter of the entire moon. The icon we used for the “quarter moons” in the figure, however, is that of a crescent moon, with closer to one quarter of the disk illuminated. We had switched the icon for the “quarter moons” from a depiction of three quarters of the disk illuminated to one quarter of the disk illuminated to match this commonsense language.
Beier (2006) had adapted the graphic from McFarland et al. (1999), who cited their sources as Blaxter (1970) and Brown (1952). It was McFarland et al. (1999) who introduced the error. They correctly copied the illumination line from a moon with three-quarters of the face illuminated (a gibbous moon) and incorrectly labeled it as “quarter moons.” They had three-quarters of the face illuminated in the icon, which was correct, but inconsistent with the label.
Illuminations produced by the sun and moon as reported by McFarland et al. (1999). Note that “quarter moons” identifies the same line as a three-quarter moon in Brown (1952) once the conversion from footcandles to lux is made.
Compare the figure from McFarland et al. (1999) with the figure produced by Brown for the Department of Navy in 1952. The Brown figure is in footcandles.
Illumination produced by the phases of the moon reported by Brown (1952). The text “1st and 3rd Quarters” indicates the “apparent half moon.”
The 1952 Brown report provides curves of illumination from the moon at four phases: full (phase angle 0º), three-quarters full (phase angle 60º), half full (phase angle 90º, which is technically a “quarter moon”) and one-quarter full (phase angle 120º). In the McFarland et al. (1999) diagram, two curves are given: one for the full moon and one for “quarter moons.” The full moon line is correct. The “quarter moons” line is the same as the three-quarters full moon in Brown (1952), meaning that the lunar disk is three-quarters illuminated (phase angle 60º) and not a “quarter moon” in the sense of one quarter of the disk being illuminated or even a quarter moon meaning one quarter of the entire moon visible and illuminated (half of the disk visible and illuminated).
Unfortunately, this error propagated forward to Beier (2006), our 2016 report (which is being reissued with a corrected figure), and Gaston et al. (2014), who changed the icon to a crescent moon (as we did in our report) and might have shifted the line down slightly, but not enough to be accurate, especially given the icon depiction of a crescent moon and textual description.
Illumination from the sun and moon reported by Gaston et al. (2014). The curve for the “quarter moons” is shifted downward slightly but is an order of magnitude higher than a crescent moon (a quarter of the face illuminated) and higher than a quarter moon (half of the face illuminated).
I regret not catching the error when editing Beier’s chapter or when updating the figure in 2016. But Andrej did catch it and now the record can be set straight.
This corrected version of the figure shows maximum values for a full moon (0.3 lux) and quarter moons (0.03 lux) with the proper icon for quarter moon showing half of the face illuminated.
For the record, the approximate values for the maximum clear-sky illumination from the moon directly overhead at its phases are as follows.
|
Phase Angle |
Brown (1952) (lux) |
(Krisciunas & Schaefer 1991) (lux) |
|
| Full 100% illuminated |
0º |
0.37 |
0.423 |
| Gibbous 75% illuminated |
60º |
0.10 |
0.071 |
| First and Last Quarter 50% illuminated |
90º |
0.043 |
0.028 |
| Crescent 25% illuminated |
120º |
0.013 |
0.008 |
These values can vary based on the distance between the sun and the moon and whether the moon is waxing or waning because of the differing characteristics of the face of the moon. Illuminations this high are unlikely to occur under most circumstances, especially at temperate latitudes. A working estimate of illumination from the full moon is closer to 0.1 lux on the ground than the ~0.4 lux potential maximum illumination, a fact that has been recently discussed by Kyba et al. (2017).
Travis Longcore, Ph.D.
August 5, 2017
Literature Cited
Beier, P. 2006. Effects of artificial night lighting on terrestrial mammals. Pages 19–42 in C. Rich, and T. Longcore, editors. Ecological consequences of artificial night lighting. Island Press, Washington, D.C.
Blaxter, J. H. S. 1970. Light, Animals, Fishes. Pages 213–230 in O. Kinne, editor. Marine ecology: a comprehensive integrated treatise on life in oceans and coastal waters. Wiley-Interscience, London.
Brown, D. R. 1952. Natural illumination charts. Research and Development Project NS 714-100. Pages 1–11, 43 plates. Department of the Navy, Bureau of Ships, Washington, D.C.
Gaston, K. J., J. P. Duffy, S. Gaston, J. Bennie, and T. W. Davies. 2014. Human alteration of natural light cycles: causes and ecological consequences. Oecologia 176:917–931.
Krisciunas, K., and B. E. Schaefer. 1991. A model of the brightness of moonlight. Publications of the Astronomical Society of the Pacific 103:1033–1039.
Kyba, C., A. Mohar, and T. Posch. 2017. How bright is moonlight? Astronomy & Geophysics 58:1.31–31.32.
Longcore, T., and C. Rich. 2016. Artificial night lighting and protected lands: Ecological effects and management approaches. Natural Resource Report NPS/NRSS/NSNS/NRR—2016/1213. National Park Service, Fort Collins, Colorado.
McFarland, W., C. Wahl, T. Suchanek, and F. McAlary. 1999. The behavior of animals around twilight with emphasis on coral reef communities. Pages 583–628 in S. N. Archer, M. B. A. Djamgoz, E. R. Loew, J. C. Partridge, and S. Vallerga, editors. Adaptive mechanisms in the ecology of vision. Kluwer Academic Publishers, Dordrecht.
CubeSats to measure light pollution
I had the fortune of being able to offer some examples of environmental applications in a paper by Dee Pack and Brian Hardy from Aerospace Corporation for the Small Satellite Conference this summer in Utah. We (mostly they) show the feasibility of using small satellites to measure upward radiance from Earth at night, with examples ranging from the Middle East to Southern California. I’m glad to have offered the concept of “darkest path” modeling for wildlife connectivity and perspectives on the usefulness of spectral information at this scale. The work we have been doing with the VIIRS Day-Night Band shows up for the identification of a very bright greenhouse on the Oxnard Plain. Here is the citation, abstract, and download link.
Pack, D. W., B. S. Hardy, and T. Longcore. 2017. Studying Earth at night from CubeSats. Proceedings of the 31st Annual AIAA/USU Conference on Small Satellites, Leo Missions, SSC17-WK-35.
This paper presents examples of the latest imaging data of the Earth at night from multiple CubeSat platforms. Beginning in 2012, with AeroCube-4, The Aerospace Corporation has launched multiple CubeSat platforms in different orbits equipped with a common suite of CMOS sensors. Originally designed as utility cameras to assist with attitude control system studies and star sensor development, we have been using these simple camera sensors to image the Earth at night since 2014. Our initial work focused on observing nighttime urban lights and global gas flare signals at higher resolution than is possible with the VIIRS sensor. To achieve optimum sensitivity and resolution, orbital motion is compensated for via the use of on-board reaction wheels to perform point-and-stare experiments, often with multiple frame exposures as the sensor moves in orbit. Ground sample distances for these systems range from approximately 100 to 130 meters for the narrow-field-of-view cameras, to 500 meters for the medium-field-of-view cameras. In our initial work, we demonstrated that CMOS sensors flown on AeroCube satellites can achieve a nighttime light detection sensitivity on the order of 20 nW-cm-2-sr-1. This resolution and sensitivity allows for detection of urban lighting, road networks, major infrastructure illumination, natural gas flares, and other phenomena of interest. For wide-area surveys, we can also program our cameras to observe regions of interest and co-add pixels to reduce the data bandwidth. This allows for a greater number of frames to be collected and downloaded. These results may then be used to task later satellite passes. Here, we present new examples of our nighttime Earth observation studies using CubeSats. These include: 1) detecting urban growth and change via repeat imaging, 2) investigating the utility of color observations, 3) spotting major sources of light pollution, 4) studying urban-wildland interface regions where lighting may be important to understanding wildlife corridors, 5) imaging lightning and cloud cover at night using wide-area imaging, 6) observations of the very bright lights of fishing boats, and 7) observing other interesting natural phenomenon, including airglow emissions, and the streaking caused by proton strikes in the South Atlantic Anomaly. Our ongoing work includes utilizing a diversity in overpass times from multiple satellites to observe nighttime scenes, imaging high-latitude cities not optimally accessed by the international space station’s cameras, and building a catalogue of observations of rapidly developing megacities and global infrastructure nodes. Data from CMOS sensors flown in common on 5 different AeroCubes in 4 different orbits have been collected. Our results show that enhanced CubeSat sensors can improve mapping of the human footprint in targeted regions via nighttime lights and contribute to better monitoring of: urban growth, light pollution, energy usage, the urban-wildland interface, the improvement of electrical power grids in developing countries, light-induced fisheries, and oil industry flare activity. Future CubeSat sensors should be able to contribute to nightlights monitoring efforts by organizations such as NOAA, NASA, ESA, the World Bank and others, and offer low-cost options for nighttime studies.
