Using dark infrastructure to combat artificial light at night

Species that are adapted to darkness rely on light from the moon to search for shelter, food, and mates. Artificial light at night – often recognized as the orange glow that brightens the night sky over urbanized areas – has disrupted spatial cues for species that rely on nocturnal rhythms. Artificial light pollution acts similar to physical barriers such as fences and roads by impeding the movement of species that avoid light, further compounding the effects of habitat loss and fragmentation.

Green infrastructure in urban areas can create corridors that facilitate species movement in fragmented terrestrial and aquatic habitats, and is recognized by the IUCN as a key spatial planning tool.

Sordello, R., Busson, S., Cornuau, J. H., Deverchère, P., Faure, B., Guetté, A., Hölker, F., Kerbiriou, C., Lengagne, T., Le Viol, I., Longcore, T., Moeschler, P., Ranzoni, J., Ray, N., Reyjol, Y., Roulet, Y., Schroer, S., Secondi, J., Valet, N., Vanpeene, S., Vauclair, S. 2022. A plea for a worldwide development of dark infrastructure for biodiversity–Practical examples and ways to go forward. Landscape and Urban Planning 219: 104332.

However, many of these areas do not take into consideration the effects of light on movement and dispersal. Since light pollution can be seen up to one hundred kilometers from the source, it is pervasive even within protected areas. In Europe, artificial light at night has increased in protected areas by 15% over an 8 year time.

To reduce the detrimental effects of artificial light, researchers are advocating for the integration of ‘dark infrastructure’, where creating dark spaces is an additional consideration when designing wildlife corridors at the landscape scale. New research identifies a four step operational process for incorporating dark infrastructure into regional plans to reduce the effects of artificial light on species.

Step 1: Map the quality of dark spaces in natural and urban settings by identifying the sources of the light pollution and its spatial distribution in relation to the species of concern.

Step 2: Identify areas of optimal habitat that are currently undisturbed by light pollution to form the foundation of dark infrastructure. Areas of lower darkness quality that are currently protected but were not created by taking ALAN into consideration can be selected if artificial light in these areas meet minimum light thresholds for sensitive species.

Step 3: Preserve dark infrastructure by enacting action plans that limit the creation of additional light sources and/or limit light intensity and unnecessary use; and restore dark infrastructure through regulation of urban lighting periods in order to match natural light rhythms.

Step 4: Monitor the efficacy of areas protected with dark infrastructure in restoring darkness and ecological function of nocturnal species.

Currently there are many dark infrastructure projects that have been carried out in Europe and the United States. As the development of dark infrastructure progresses, it will bring attention to knowledge gaps and identify many opportunities where existing protected areas could be enhanced by incorporating dark infrastructure.

More research is needed to better understand the response of species function on the various dimensions of light pollution, such as the direction of light, light intensity thresholds, and the response of light across the spectrum while utilizing current data on dispersal ecology of target species. As light pollution levels increase worldwide, dark infrastructure is a useful planning strategy that could limit the effects of light pollution at the landscape level.

State	Year	Policy	Description
New Hampshire	2026	SB592	Enables regional, conservation, and energy resource planning for habitat strongholds and wildlife corridors
New Hampshire	2019	SB200	Requires the New Hampshire Department of Transportation to consider fish and wildlife crossings and mitigation measures in all future road and culvert projects
New Hampshire	2016	SB376	Requires the fish and game department to identify existing and needed wildlife corridors connecting wildlife habitats in the state and to make recommendations for legislative changes

State	Year	Policy	Description
Maine	2023	LD258	Appropriates $7.5 million to Department of Transportation to improve roadways with potential adaptations for wildlife
Maine	2023	LD1881	Establishes compensation fee program relating to fish and wildlife habitats and associated corridors, including compensation paid by solar energy development
Maine	2023	LD508	Requires Department of Environmental Protection to review its permitting laws concerning climate change, habitat connectivity, ecological resilience, and coastal environments

State	Year	Policy	Description
New Jersey	2025	S3618	Directs state agencies to develop a Wildlife Corridor Action Plan
New Jersey	2024	S3916/A5486	Expands eligibility for existing wildlife fencing programs by including farmers leasing farmland
New Jersey	2007	NJAC7:13	Requires the state to incorporate wildlife crossings or a natural bank for terrestrial threatened and endangered species and/or species of concern when a new bridge or culvert project would cause habitat fragmentation

State	Year	Policy	Description
New Mexico	2023	SB72	Appropriates money to new Wildlife Corridors Fund for implementation of wildlife crossing projects under New Mexico Wildlife Corridor Action Plan
New Mexico	2022	HB 2	Allocates funding for projects to reduce wildlife-vehicle collisions and allows the Department of Transportation and Department of Game to implement their Wildlife Corridors Action Plan
New Mexico	2019	SB 228	Requires the creation of a Wildlife Corridor Action Plan that includes comprehensive guidance to agencies for identifying, prioritizing and maintaining important areas for wildlife movement

State	Year	Policy	Description
Washington	2023	HB1216/SB5196	Requires Department of Ecology to prepare environmental impact statements for clean energy projects that consider impacts to habitat connectivity and wildlife migration corridors
Washington	2022	SB5689	Provides funding for US 97 Wildlife Crossing Improvements project
Washington	2019	SEO 1031.02	Recognizes the effect of roadways in creating barriers to wildlife movement, breeding, and migrations; the Washington State Department of Transportation will promote and support Practical Solutions and Planning and Environmental Linkages to integrate habitat connectivity and biodiversity plans; will make use of the highway prioritization map known as Habitat Connectivity Investment Priorities; and will corporate and coordinate with other agencies involved in wildlife habitat protection, specifically along highways

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Using dark infrastructure to combat artificial light at night

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About the Author: Fahimeh Baziari

State	Year	Policy	Description
Vermont	2023	Act59	Vermont's 30x30 law that commits to conserving and maintaining an ecologically functional landscape that sustains biodiversity and maintains landscape connectivity
Vermont	2016	Act 171	Primarily focuses on timber harvesting regulations, but calls for a study of necessary revisions to planning statutes that protect contiguous areas of forestland from fragmentation and promote habitat connectivity between forestlands

State	Year	Policy	Description
Colorado	2026	SB141	Creates optional collision prevention fee to fund wildlife safe passage projects
Colorado	2025	HB1093	Restricts local limits on residential density unless offset elsewhere, exempts areas near wildlife crossings, and allows municipalities to seek judicial review of land use initiatives
Colorado	2023	SB 23-092	Encourages minimal impacts to wildlife migration corridors when constructing solar panel farms
Colorado	2023	SB 214	Appropriates funding to the Colorado Wildlife Safe Passages Fund for wildlife crossing projects
Colorado	2022	SB22-151	Creates a $5 million fund for measures that reduce wildlife-vehicle collisions and reconnect habitat fragmented by roads
Colorado	2022	HB22-1072	Expands the scope of Habitat Partnership Program to fund efforts to conserve wildlife migration
Colorado	2021	SJR 21-021	Aims to protect and enhance habitat connectivity in the state through the establishment of a working group to develop state policies on corridors, as well as the commission of a report on state corridors and voluntary policies to support willing landowners in improving connectivity
Colorado	2019	EO 11	Directs Colorado agencies to identify policy, regulatory, and legislative opportunities to ensure the ongoing conservation of seasonal big game habitat and migration corridors
Colorado	2018	SB 18-143	States explicit goals for Division of Parks and Wildlife to invest in habitat conservation and wildlife crossings

State	Year	Policy	Description
Florida	2024	SB1638	Dedicates annual funding to land purchases, conservation easements, and trail maintenance within Florida Wildlife Corridor
Florida	2023	HB1379	Creates annual appropriation to acquire lands that complete certain linkages and are under high population stress within Florida Wildlife Corridor
Florida	2023	SB2500 sec.146	Provides funding to buy Ocala to Osceola (“O2O”) Wildlife Corridor
Florida	2021	SB976	Tasks state agencies with maintaining wildlife connectivity and designates Florida Wildlife Corridor as an existing physical, geographically defined area
Florida	2021	SB2500	Appropriates $300 million to acquire lands to conserve Florida Wildlife Corridor
Florida	2019	SB7068	Creates a "Multi-use Corridors of Regional Economic Significance Program" that includes protection of wildlife corridors as an intended benefit
Florida	2008	SB542	Amends Florida Forever Act statues to include goals of connecting linkage corridors
Florida	2001	SB1468	Amends Florida Forever Act to establish that land acquisitions should include complete landscape linkages and corridors
Florida	1999	S908	Creates Florida Forever Program, with increased protection of lands that protect threatened or endangered species and plans to create a statewide system of connected landscape linkages