Bat friendly lighting in the public realm – a case study

Research and trials have confirmed that wildlife is heavily reliant on good urban planning and sensitive product choice for successful ecological outcomes. In particular, over-lighting, and directional spill can harm bat habitats. Attitudes are changing now but, leading bat researchers have challenged the industry, wondering if LEDs are “conserving energy at the cost of biodiversity”

Bat species continue to decline as a result of habitat destruction and fragmentation. Yet the economic and ecological value of protecting these species is not as widely understood as it should be. Bats play a key role in urban ecosystems, through insect and pest control, seed dispersal and pollination of a wide range of plants and crops.

The outdoor lighting industry is responding.

Recent changes to BS5489 have been thoughtfully and deliberately crafted to prioritise environmental protection, ensuring bat-friendly lighting schemes and similar start to become the norm. (Read our blog post series on the changes here) And our products are smarter, offering greater flexibility to deliver the kind of product differentiation and design concessions that conservation biologists ask for. We can light for people whilst also reducing negative environmental impacts; using direction, duration, intensity, and spectrum.

It falls to us as lighting manufacturers, to help councils duty-bound to balance their legal and moral obligations. We must do our part in providing lighting solutions that strike a balance between lighting that improves human use of space as well as protecting and encouraging wildlife’s use of the same.

Environmental Standards in Action

This was exactly what London Borough of Barking and Dagenham achieved with its “Ripple Greenway project” The scheme involved creating a brand new path for people on foot and bicycle, linking the Thames View community with its nearby Nature Reserve and River Thames footpath. The traffic-free link also provides access to a new Overground station which was under construction. Residents said they didn’t currently use the green space because they didn’t feel safe. They wanted improved access and visibility along the site as well as catering for a wide range of users. They asked for a cleaner environment and improved wildlife habitats.

An investigatory ecological survey of the Greenway and nature reserve areas revealed bat roosts and several species of bats inhabiting the location. With its overgrown watercourse, the site was shown to be an important wildlife corridor – a Site of Importance to Nature Conservation (SINC).

The river that runs adjacent to the Ripple Greenway footpath

The path, therefore, had to be carefully designed to ensure that wildlife habitats would thrive in the future. Opening up the green space within a highly urbanised environment was also an opportunity to promote mental and physical health and wellbeing for local schools and residents

In collaboration with the community, the design included new lighting, new trees and planting, benches, bins, wayfinding signs, information boards, heritage and memorial features, natural play features and new wildlife habitats such as bird and bat boxes, bug hotels (made by school pupils) as well as planting such as blossoming trees to attract beneficial insects and bees.

Community engagement

Path in disrepair

Concept design - path

Concept design - orchard

Initial Project Lighting Specification

INDO SiCURA luminaire with PIR Sensor fitted to Zhaga socket for part-night dimming
Lighting for safety and access over 1.5km of open space/greenspace path including small, currently unlit, joining footpaths
Mix of existing luminaire replacement and new luminaires
Designed to be lit to lighting class, P4
Mounted on 5M raise & lower columns, painted black
Light shields for additional or ongoing light control, as needed

Pre scheme light monitoring was conducted by Ecologists to demonstrate the existing light levels on the proposed site and identify any areas particularly sensitive to lighting. INDO was asked by the consultant ecologist (specialising in biodiversity and urban green infrastructure from University East London) to clarify how the lighting proposal would comply with the lighting limitations that are now recommended for habitats of value to Bats and other sensitive wildlife.

How the INDO lighting scheme was adapted to suit Ripple Greenway’s bat habitats

a) Lighting Direction

Light must be focused on the pedestrian zone, to improve public access and safety, tightly directed to prevent minimise light spill onto the watercourse, identified wildlife habitats and adjoining properties.
Lighting level on the watercourse to be kept below 1 lux across the majority of the calculation.
The upward light ratio to be 0%

INDO Response:

The image below shows the light characteristics of the proposed INDO SiCURA. It can be seen that at 90degrees the intensity of light output is 0.00 indicating no lighting at or above the horizontal plane. Additionally, the scheme’s lighting design limited the mounting height to 5M with no tilt to target only to the calculation area; and photometric performance was optimised to minimise light spill into unwanted areas. Should further light control be needed, a full range of rear, side and front shields is available for SiCURA and can be fitted without drilling or tapping on site.

b) Lighting Duration

Turning lights off is one of the most effective ways of reducing the unintended, adverse effects of lighting on wildlife
Sensors should trigger light only when needed
Dimmers/timers must provide a ‘dark period’

INDO Response:

The SiCURA luminaire supports dimming and part-night lighting. Units are remotely managed by the (Urban Control) Central Management System (CMS) for lighting output and ON/OFF switching times. Timings can be changed to meet the dynamic requirements of the habitat as the seasons change. The PIR sensor, connected via Zhaga socket, is dimmed to 25% output when no activity is detected, coming up to 100% when the sensor is triggered, then dimming back down to 25% after 5 minutes of inactivity. An adaptive, part-night dimming function, further reduces light spill onto the riverway and lowers energy consumption.

c) Lighting Intensity

Lighting Spectrum – Behavioral responses of wildlife varies according to spectrum. However, as a general rule, lower CCTs are less disruptive to wildlife and the environment
“Warm light’ colour temperature – ideally 2700K”
“Luminaires should feature a peak wavelength of >550 nm to avoid the component of light most disturbing to Bats.”

INDO response:

The INDO SiCURA product range is available from 2700K colour temperature LED’s. The initial design was for 3000K but this was later reduced to 2700K. It was important, however, that the luminaire also displayed the requisite peak intensity (this is a different factor from colour temperature). SiCURA’s spectral output peaks at 600nm wavelength, avoiding a spike in the blue area as required (see graph below)

Chart showing the spectral output of the LED chips used in SiCURA

INDO initially designed the scheme to the lower end of lighting-class, P4, achieving the standard but keeping levels as low as possible. The customer subsequently decided the path should have the capability to be lit to class P3 but dimmed to P4 if necessary. To accommodate this, INDO increased the lumen package of the SiCURA from 1.5klm to 2.5klm whilst keeping the rest of the design parameters unchanged.

As can be seen in the video, lighting levels on the path were limited to a minimum required for public use of the space whilst also achieving a satisfactory perception of safety.

Installation Gallery

Lighting and Ecology working in harmony!

References:

The Institute of Lighting Professionals and the Bat Conservation Trust have both co-authored and produced guidance on the reduction of obtrusive light, undertaking environmental lighting impact assessments and the impact of obtrusive lighting on Bats.