The Illuminating World of Bridges, Part 4. Ecology Now!

Learn about bridge eco-systems (with links to Parts 1, 2, 3)

PART 4 ECOLOGICAL CONCERNS

Welcome engineers, architectural designers, and interested colleagues to the fourth edition of five "Illuminating World of Bridges." (Editions 1 through 3 are linked below)

Thank you for the many email responses, including requests for ecological systems and biodiversity coverage. Here it is! Issue #4 describes the "stressor" effect that increasing urbanization has on organisms —specifically from "anthropogenic" light, or light created by humans through artificial and electrical sources.

While many bridges cross bodies of water, a significant number also span land, roads, and other infrastructure. In this issue, we focus on signature bridges that connect land to land across water. The design, engineering, and lighting of these structures require consideration of the sensitivities of nocturnal fish, waterfowl, and amphibians, as well as birds and insects.

With an eye to providing you, our readers with resources, there is a free "Global Eco Research Guide" document attached at the end of this newsletter.

The design team begins by conducting an existing-conditions study. From an ecological standpoint, nocturnal wildlife is identified by consulting knowledgeable resources—including local and federal authorities, as well as NGO's.

The effects on human communities must be balanced with the effects on surrounding flora and fauna. As examined in Part 1, civic benefits of illuminated bridges reflect positive human outcomes—connectivity, safety, well-being, and social and economic vibrancy, particularly when pedestrian and cycling lanes are indicated. While ecological impacts are often viewed as inherently negative, best practices have been developed to minimize adverse environmental effects.

"You can't think about environmental impacts without thinking about impacts on people." —Jim Anderson, SiteLights

PLACES, HUMAN & NON HUMAN LIFE

Specific locations and geographies host specific wildlife. Artificial light can affect a range of evolutionary dependencies for birds, bats, fish, and invertebrates and other living organisms. For example, illumination of waterways can create behavioral barriers and migratory delays for numerous fish species. Similarly, lighting along riverbanks and lakes may disrupt predator-prey relationships among insects.

Human considerations begin with community outreach and project introductions to gather useful input. The community topic will be covered in detail in the next installment of the Illuminating World of Bridges. For bridge users—whether traveling by vehicle, on foot, or by bicycle—visual comfort, including contrast and glare, should be carefully evaluated during the design phase. Finally, light trespass and glare should be mitigated for surrounding homes and public spaces.

Illuminated River is a multi-site, permanent light-art installation embellishing the historic Thames River bridges. The design process required a delicate balance of community desires, ecological considerations, and the artist's vision.

Luminance studies of the river and it's banks were conducted both before and after the installation enabling analysis of the lighting levels on the banks and water surfaces.

By establishing benchmarks based on ambient light levels and existing conditions, the project team carefully monitored the effects of their installation. Using baffles and directing light upwards into the covered areas of the bridges, the team was able to concentrate illumination on areas most impactful to humans while minimizing overall light exposure at the water's surface.

How does the design team identify ecological concerns, species-specific sensitivities, or protected wildlife in the area? Guidelines may not be included in the lighting design brief and lighting designers are not species experts! However, as mentioned: Designers may have a hand in shaping marine ecosystems. *See below for resources and prompts to contact local wildlife authorities.

Pre-design site assessment is critical for both the bridge structure and its surrounding river, bay, or ocean environment. Identifying the specific wildlife species, and understanding their sensitivities to light, is essential for the ecosystem-aware designer. Existing light levels should be mapped during this assessment.

For lighting concepts, a detailed photometric analysis is conducted to simulate design options, including alternative optics, color temperatures, brightness, and contrast. This analysis quantifies light spill and evaluates direct visibility impacts on sensitive zones within the local ecosystem, ensuring both environmental responsibility and functional effectiveness.

A special thank you to Jim Anderson, of SiteLight for his support and input.

Did you miss Illuminating World of Bridges' previous three chapters? They are evergreen, so get your reading glasses on.

Part 1 introduces the exciting practice of bridge illumination. Part 2 explores luminous colors and international trends. Part 3 provides a technical focus.

Notable Articles:

1. Davies, T. W., & Smyth, T. (2018). “Why artificial light at night should be a focus for global change research in the 21st century.” Global Change Biology. https://onlinelibrary.wiley.com/doi/10.1111/gcb.13927

2. Jägerbrand, A. K., & Spoelstra, K. (2023). “Effects of anthropogenic light on species and ecosystems.” Science, 380. https://www.science.org/doi/10.1126/science.adg3173?utm

Research Insights from Pacific Northwest National Laboratory (PNNL):

1. Lighting Science and Technology Laboratory: This facility studies connected lighting systems, aiming to improve lighting quality and reduce environmental impacts.

2. Lab-on-a-Fish (2021 R&D 100 Award winner): This innovative biotelemetry sensor monitors the health, behavior, and environment of fish, providing valuable data for studying the impacts of artificial lighting on aquatic species

Resource Link Download

Global Eco Research Guide