C. Aubrecht, M. Stojan-Dolar, A. de Sherbinin, M. Jaiteh, T. Longcore, and C. Elvidge

In this paper we argue for the importance of an “urban lighting governance” framework, i.e. control and management of artificial night lighting, particularly in close proximity to protected areas, and raise awareness of the issue of light pollution and related ecological consequences. The term light pollution is widely used referring to any adverse effect of artificial light, including sky glow, glare, light trespass, light clutter, decreased visibility at night, and energy waste.

The footprint of human occupation is uniquely visible from space in the form of lights at night, ranging from the burning of rainforest to massive offshore fisheries to the omnipresent lights of settlements and connecting road networks (Elvidge et al. 2001). Increasing research activities on the ecological consequences of artificial night lighting in recent years have attracted the attention of both scientists and journalists (Rich & Longcore 2006, Aubrecht et al. 2008a, Klinkenborg 2008). We present a study using nighttime Earth Observation data that helps to identify which protected areas globally are most exposed to human influences.

Lighting governance in this article is described in terms of existing legal implementations and ongoing efforts in regulating adverse effects of artificial light at night. We focus in particular on the emerging trend of Dark-Sky Parks that protect areas with a natural dark sky coupled with promotion of tourism and educational and public awareness programs for visitors and local municipalities at and around such sites. Monitoring lighting conditions from space enables consistent global assessment of light pollution trends and focusing on areas of special need (e.g., biodiversity hot spots, rare ecosystems). This offers valuable reference information and a foundation for developing policy questions relevant to sustainable management and conservation of ecosystems.

Lighting governance

With growing awareness of the problems related to excess artificial lighting, there is a need for legislation that would limit the rapidly increasing levels of light pollution. The initiatives that draw the attention to this need are present in various European countries as well as in several U.S. states and mostly come from NGOs and the academic sphere. The internationally recognized coordinating authority on light pollution is the International Dark-Sky Association (IDA) which was founded in 1988 and since then has been a platform for promoting public awareness of the hazards of light pollution.

The first “sky law” that limits light pollution was enacted in 1988 in Canary Islands to protect the Islands’ astronomical observatory sites (Ruggles & Cotte 2010). Later, most important observatories adopted legal regulations protecting them from light pollution. Among larger areas not restricted to observatories, the Italian Region of Venetto was the first to adopt light pollution legislation in 1997. Today, 12 out of 20 Italian regions have light pollution laws demanding 0% upward light output ratio and an additional 6 regions have legislation with various levels of protection against light pollution. The Lombardy regional law served as a model for national legislation in Slovenia, where in August 2007 a “Decree on Limit Values due to Light Pollution of Environment” was adopted, prohibiting light above the horizontal and requiring the use of shielding for most luminaires. It also defines acceptable illumination for airports, ports, railways, production premises, businesses, institutions, construction sites and advertising panels, and limits the yearly electricity consumption that municipalities may use for public lighting.

In the United Kingdom (England, Scotland, Wales) since 2005, (artificial night) lighting has been categorized as a statutory nuisance in the context of potential prejudicial health conditions (as defined in the “Clean Neighbourhoods and Environment Act 2005”). Not in principle intended to fight light pollution and its ecological consequences, this law should nonetheless help reduce lighting that shines into windows. However, a potential major problem in terms of law enforcement exists in this context, as the responsible governing body (i.e., the Chartered Institute of Environmental Health), has not openly supported the law (Morgan-Taylor 2006).

Furthermore, the IDA maintains a Directory of Lighting Ordinances currently listing various legislative acts and statutes for 19 of the 50 U.S. federal states. There is no consistent or standardized way in terms of the handling of these legal measurements. Most statutes deal with light pollution differently and in varying contexts (e.g., the Arizona House Bill Title 47 Chapter 7, the California Energy Commission Title 24, the Arkansas Shielded Outdoor Lighting Act, etc.). On the national level, however, the U.S. Environmental Protection Agency (EPA) does not address light pollution in its latest “Report on the Environment”, despite urgent recommendations of its own Scientific Advisory Board in 2007: the board identified light pollution as a “significant potential future environmental stressor that risks disrupting animal and plant physiology and behavior”, and stated that “this risk should be managed” (Davis 2007).

‘Rules for lighting’ are proposed and related fights for legislative measures are on-going in several other countries, such as the Czech Republic (Hollan 2003), Switzerland (Righetti 2007), and Germany (Hänel 2009). In 2002, the Czech Republic became the first country to enact nation-wide legislation that specifically mentions light pollution. However, it does not provide specific technical prescriptions and limitations. Compliance with this ‘Protection of the Atmosphere Act’ (an English translation of the Act is provided by IDA Czech Republic), which also addresses other kinds of air pollution, is not mandatory, and as a result, its recommendations are being followed to a very limited extent (Mizon & Morgan-Taylor 2008). Although adopting laws that limit light pollution is of crucial importance, successful implementation of the regulations is an important next step that can represent a problem in some areas. Raising the awareness of local decision-makers as well as of the general public about the light pollution-related issues can be of great importance in this respect and can contribute significantly to a general acceptance of (or even demand for) the required limitations.

Monitoring Artificial Night Lighting From Space

The footprint of human occupation is uniquely visible from space in the form of lights at night. The National Oceanic and Atmospheric Administration, National Geophysical Data Center (NOAA-NGDC) processes and archives data acquired by the U.S. Air Force Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS), which was initially designed to monitor the global distribution of clouds using visible and thermal infrared spectral bands. At night, the visible band signal is intensified with a photomultiplier tube enabling the detection of moonlit clouds. The boost in gain provides this sensor with the unique capability of observing lights present at the surface of the Earth at night. Most of the lights are from human settlements (Elvidge et al. 1997) and ephemeral fires (Elvidge et al. 2001a). Furthermore, gas flares and offshore platforms as well as heavily lit fishing boats can be identified. NOAA-NGDC archives the long-term DMSP data from 1992 to present. Individual orbits are processed with automatic algorithms (described in Elvidge et al. 1997, 2001b) identifying image features, such as lights and clouds, and quality of the nighttime data. Cloud-free annual composites of nighttime lights at a spatial resolution of 30 arc seconds, corresponding to approximately one kilometer at the equator, are produced regularly for every year and are publicly provided for download at the NOAA-NGDC-DMSP website. Figure 1 shows a sample composite of the Earth at night as seen from space.

Artificial Night Lighting (ANL) In Protected Areas – A Proxy For Human Activity

Protected nature areas represent the parts of our planet with high biodiversity where nature is relatively undisturbed. It is of particular importance to maintain natural conditions during both day and night time in these areas. There is a growing body of evidence showing that artificial night lighting affects the foraging, reproductive and migration behavior of a number of nocturnal animals such as insects, bats, amphibians and birds. It changes prey-predator relationships, affects animal natural rhythms, and disrupts physiological processes in plants (Rich & Longcore 2006). High levels of light pollution in proximity of protected areas are therefore especially worrying.

Moreover, nighttime lighting can also be considered as a proxy for anthropogenic activities that bring along a number of other environmental disturbances and influence neighboring regions. This enables a globally consistent analysis of areal exposure to potential human impacts. The assessment of exposed ecosystems, potential threats and related loss of biodiversity is essential in the context of monitoring and protecting the diversity of life on Earth, which is considered one of the ‘global issues’ affecting society.

UNEP’s World Conservation Monitoring Centre (WCMC) provides information on spatial distribution and delineation of protected areas (World Database on Protected Areas, WDPA). Integrating these data and the DMSP nighttime lights data, a set of spatial indicators was developed that describe the exposure of protected areas to artificial night lighting on a global scale. In addition to this direct ANL exposure (Protected Areas Light Pollution Indicator, PALI), a 5-kilometer neighborhood designated around lighting sources was additionally considered in order to account for potential outreaching human influence on protected areas (Protected Areas Human Influence Indicator, PAHI). In fact, the direct effects of light pollution do not stop at the borderline of a distinct lighting source. Light emitted from human settlements in the atmosphere is refracted or scattered by air and water molecules and suspended particles (atmospheric aerosol) caused by dust, pollen, salt from sea spray, and waste products from industry. Artificially illuminating the sky over great distances this is called “artificial skyglow”. Light from cities has been documented as being visible from over 200 miles (more than 320 km) away (Moore 2001, 2007). Thus, the 5-kilometer buffer width has to be understood as a kind of arbitrary value and is undoubtedly highly variable for every individual case. Nonetheless, this little addition gives an idea of how much potential impact values can change by just minimal increases of the basic spatial units (see results in Table 1).

Initial results of the analysis (Figure 2) indicate that protected areas in Europe and Asia Minor, the Caribbean, South and East Asia as well as in the Eastern United States are most exposed to anthropogenic light pollution (Aubrecht et al. 2010). Introducing aggregated data on terrestrial biomes (Olson et al. 2001) reveals that protected areas in temperate broadleaf and mixed forests are most affected. Biomes are defined as broad terrestrial ecological regions that are composed of finer-scale ‘ecoregions’ being sensitive to more specific ecological patterns. As explained by CIESIN (2009) such ecoregions might be more appropriate as policy targets, since they identify areas based on factors that affect biodiversity on the ground more precisely than biomes. However, given the scale and resulting computational requirements of the presented study (global 1-km grids for both the DMSP and the WDPA data) it was decided to use the coarser-scale biome data as basic reference units of the analysis.

Table 1 shows the total protected area on a global scale, classified by biomes. PALI and PAHI index values are given for each category. For some biomes, large indicator value differences are striking given that only an added 5-kilometer buffer around lighting sources on the ground accounts for these increases. This illustrates that potential threats to protected areas are mostly in very close proximity, even if basically being outside the protected area.

The exposure of regional biomes to indicators of human influence calculated by nighttime lights are in accordance with a previous assessment of biomes at risk where global land cover data were used as indicators for human impact (Hoekstra et al. 2005). With regard to considering remotely sensed nighttime lights as proxy measure for human activity (e.g., Aubrecht et al. 2008b, Ziskin et al. 2008), we need to be aware of certain issues in that context. Various regions of the Earth are characterized by very sparsely distributed light patterns compared to high population density (e.g. Africa). Elvidge et al. (2010a) showed those effects when jointly analyzing DMSP nighttime lights and spatial population data (Landscan) to assess electrification rates on a global scale.

Derivates of DMSP data were already used previously to estimate light pollution in U.S. Class 1 Federal Areas (1997 Light Pollution Study). These artificial sky brightness maps were modeled using radiance calibrated nighttime lights as input to a radiative transfer model. However, radiance calibration is not yet implemented in operational DMSP products, which is why standardized stable lights data are used for the current study.

Special Protected Areas: Dark-Sky Parks

During the last decade there has been an emerging trend to protect areas with natural dark sky, promote tourism at such sites and establish educational and awareness-raising programs for visitors and local municipalities. There are currently 21 official dark-sky parks worldwide (according to the IUCN Dark Skies Advisory Group’s List of Dark-Sky Parks and the International Dark-Sky Association IDA). They are mostly designated by two authorities that use slightly different systems of designation. First, the IDA uses the terms “International Dark-Sky Park (IDSP)” and “International Dark-Sky Reserve (IDSR)”, where IDSPs are reserved for protected public land, whereas IDSRs can include private land and must have a peripheral zone of at least 700 square kilometers. Three categories are distinguished: gold, silver and bronze tiers, with gold having outstanding quality night skies and bronze being slightly affected by sky glow but where aspects of the natural sky are still visible. Communities with exceptional commitment to preserve or restore dark sky and a quality comprehensive lighting code can apply for the title “International Dark-Sky Community (IDSC)” (not included in the above mentioned list of parks). Second, the Royal Astronomical Society of Canada (RASC) distinguishes between “Urban Star Parks (USP)” and “Dark Sky Preserves (DSP)”. In the first case artificial lighting must be strictly controlled, but sky glow from other areas may still be seen; whereas in the second case no artificial lighting should be visible and sky glow must be negligible (Dick 2009). A buffer zone is required in both cases. Most dark-sky parks are located in North America, and two can be found in Europe (with an additional two European applications currently being processed). Notably, no officially established dark-sky areas exist on other continents where the conditions are much more favorable (Figure 2).

In addition, the Starlight Initiative (www.starlight2009.net), supported by UNESCO-World Heritage Centre, IAU (International Astronomical Union), MaB Urban Ecology Programme of UNESCO, CIE (International Commission on Illumination), OTPC-IAC (Instituto de Astrofisica de Canarias) and UNWTO (World Tourism Organization), introduced the concept of Starlight Reserves in March 2009. This designation combines protection of the natural sky with other important world heritage values: archaeological and cultural sites, astronomical observatories, protected nature areas, exceptional manifestations of the night sky, and human habitats with relatively low levels of light pollution (Marín & Orlando 2009). Starlight reserves should have a core zone with minimal effects of artificial lighting and a buffer zone where special rules for outdoor lighting apply. If larger human settlements are present in the proximity they are considered an external zone where sustainable lighting recommendations should also be implemented. The concept of Starlight Reserves is included in the ICOMOS thematic study titled “Heritage Sites of Astronomy and Archaeoastronomy in the context of the World Heritage Convention” that was endorsed by UNESCO’s World Heritage Committee in July 2010 and will serve as a basis for inscription of astronomical properties as world heritage. It introduces five dark-sky areas as case studies for Starlight Reserves (Ruggles & Cotte 2010).

In the long run, a global consent on the categorization of dark-sky areas may contribute to the general recognition of these sites by the public.

Conclusion

Our assessment and discussion of protected areas’ exposure to light pollution and related ecological consequences underscore the need for an urban lighting governance framework to protect the natural environment. There has been much debate on the control and directionality of lighting in the last two decades, but only a few countries have been able to adopt some sort of related legal implementation. The recent emerging Dark-Sky Park concept (i.e., a trend of protecting areas with natural dark sky), promoting tourism at such sites and establishing educational and awareness-raising programs for visitors and local municipalities, is a big step towards better management and conservation of the natural environment.

Considering satellite observations of the Earth at night, light pollution development can be monitored consistently on a global scale. Improved conditions that are believed to result from law-enforced management activities against light pollution were observed on the Hawaiian island of Oahu in a satellite-based analysis of trends of coral reef exposure to artificial night lighting (Aubrecht et al. 2008c, 2009). The presented analysis helps indicate which protected areas are most exposed to human influences.

It is known that lighting types vary spectrally (Elvidge et al. 2010b) and that these variations might have different effects on wildlife and general ecosystem characteristics. It is thus highly advisable that the analysis of biological effects take into account the spectral differences in lighting types. Various case studies using in situ collected data show that insects, birds and bats, for example, appear to react differently to different colors of the light (Downs et al. 2003; Eisenbeis 2006; Evans et al. 2007; Gehring et al. 2009; Poot et al. 2008). While the DMSP satellite nighttime lights are panchromatic and such effects thus cannot be considered in current remote sensing analyses, future satellite sensors may provide multispectral observations of nighttime lights (Elvidge et al. 2007), enabling more specific analysis of lighting impacts.

This call for urban lighting governance highlighting the urgent need for sustainable management of artificial light at night is an important step towards public communication and raising awareness on the topic of light pollution and its ecological consequences. Recent increased visibility in the media should be taken as an impetus for pushing forward related policy relevant activities and eventually stimulating further legal implementations.

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Author Biographies

Christoph Aubrecht is a research associate scientist at the AIT Austrian Institute of Technology (Vienna, Austria) having a degree in geography and GI science from the University of Vienna. He has been teaching at the Institute of Geography and Regional Research at University of Vienna and is a cooperative doctoral researcher at the Institute of Photogrammetry and Remote Sensing at Vienna University of Technology. He held several visiting scientist and guest researcher positions at NOAA’s National Geophysical Data Center (NGDC), as well as at Columbia University’s CIESIN and at the Spatial Sciences Institute of the University of Southern California. Since 2008, Christoph has been member of Earthzine’s editorial board and currently serves as Deputy Editor-in-Chief.

Mojca Stojan-Dolar has a PhD in biology from the University of Göttingen, Germany and specializes in behavioral ecology. She currently works for Dark-Sky Slovenia and leads the Life at Night project that deals with nature friendly illumination of cultural heritage (supported by Life+ Programme, No. LIFE09 NAT SI 378).

Alex de Sherbinin is a Senior Staff Associate for Research at Columbia University’s Center for International Earth Science Information Network (CIESIN) and serves as deputy manager of the NASA-funded Socioeconomic Data and Applications Center (SEDAC). Prior to joining CIESIN, Mr. de Sherbinin was a USAID-funded Population-Environment Fellow with the Social Policy Program of IUCN-The World Conservation Union (Gland, Switzerland), and a Population Geographer at the Population Reference Bureau (PRB, Washington, DC). From 1984-1986 he served as an agricultural extension agent with the U.S. Peace Corps in Mauritania, West Africa.
Malanding Jaiteh is a Geographic Information Specialist at Columbia University’s CIESIN.

Chris Elvidge is leading the Earth Observation Group at NOAA/NGDC (Boulder, CO, USA). After his Ph.D. in Applied Earth Science from Stanford University he was a National Research Council research associate at NASA’s Jet Propulsion Laboratory. He moved on to faculty in Biological Sciences in the Desert Research Institute at University of Nevada. Prior to coming to NGDC he was a visiting scientist in the EPA’s global change research program office in Washington, DC.

Travis Longcore is associate research professor at the GIS Research Laboratory at University of Southern California (Los Angeles, CA, USA) and science director of The Urban Wildlands Group. Together with Catherine Rich he edited ‘Ecological Consequences of Artificial Night Lighting’, published by Island Press (2006).