The London- and Edinburgh-based lighting design firm Speirs and Major Associates’ portfolio boasts a gamut of neon-hued urban landmarks, ranging from the Bridge of Aspiration in London to developments in Dubai. But a recent commission to illuminate The Sackler Crossing, a John Pawson–designed footbridge at the Royal Botanic Gardens, Kew, offered a unique exercise in subtlety: designing for a historic site while maintaining a concern for its ecology.

Situated in southwest London between Richmond and Kew, the 167-year-old Botanic Gardens is a sprawling research and education institution that has collected more than an eighth of all known plant species. When first asked to illuminate Pawson’s bridge, which spans the banks of a central lake, project designer Philip Rose wondered whether LED lighting would adversely affect the plants and historic landscapes of the Botanic Gardens. “We questioned if the bridge should be illuminated, given the possible light pollution and the environmental impact the lighting may have on the local flora and fauna,” he says.

Following the advice of the Botanic Gardens’ herbologists and ecologists, Speirs and Major developed a Minimalist design solution that complements both landscape and structure. Custom LED fittings embedded within the bridge project a warm gradient of light up each of the 1,000 freestanding bronze balustrades that enclose the walkway, creating a diaphanous perimeter that is reflected in the lake. “The lighting concept was developed to help reinforce [the architect’s] concept of walking on water, with the bridge deck seeming to float just above the water’s surface,” Rose says. Moreover, the light does not spread into the immediate habitat.

Speirs and Major also uplit a nearby cluster of trees with floodlights and ceramic metal-halide spotlights. The overall composition not only underscores the area as a visual and programmatic nexus in the gardens’ revised master plan, but allows visitors “to understand the relationship between the architecture, the water, and its natural setting,” Rose says. “It gestures toward the gardens’ long tradition of revealing ‘the picturesque.’ ”