High above the constant hum of traffic, a concrete bridge is undergoing a remarkable transformation. This isn’t just any bridge; it’s being reimagined not for the rumble of cars, but for the quiet passage of wildlife. The M1 Princes Motorway, a major artery near the Illawarra-Heathcote corridor, sees an estimated 40,000 vehicles daily. For the countless animals attempting to traverse the landscape, this busy road has become an almost insurmountable barrier, fragmenting vital habitats and threatening species survival.
However, this long-overlooked structure is now being reborn as a vital living corridor, offering a safe passage for fauna to move between fragmented ecosystems. This ambitious project represents the realisation of a vision held for nearly half a century by retired National Parks ranger Bob Crombie.
A Vision Decades in the Making
“I came up with this idea in about 1974, 1975,” Mr. Crombie recounted. “I was working in the park as a ranger naturalist, and it became apparent that [wildlife] needed to be able to move around the landscape. The movement of the species that keep those places viable has been blocked by this great big highway.”
Back in the mid-1970s, government departments were only beginning to grasp the critical importance of landscape connectivity for the survival of native species. Mr. Crombie highlighted the ecological reality of areas like the Royal National Park. “Everyone thinks it’s 14,000 hectares,” he explained, “but it’s actually a number of small units, so it is really quite threatened when you think of those units.”
Scrutinising maps, Mr. Crombie identified the potential of a forgotten crossing. “Right in the middle of one of those places with significant vegetation was this bridge, and I said, ‘Hallelujah, we’ve got a wildlife corridor.’”
Retrofitting for Nature: A Unique Approach
With the crucial support of various government departments, that vision is now becoming a reality. The project’s ingenuity lies not in constructing something entirely new, but in repurposing and enhancing an existing structure. Ecologist Kylie Madden, who is deeply involved in the project, emphasised the significance of this retrofit approach.
“This is probably one of the most exciting projects I’ve ever been involved in, in my entire career,” Ms. Madden stated. “It’s a retrofit of an existing bridge.” Originally designed for occasional service and emergency vehicle access, the bridge deck is now being meticulously converted into functioning habitat, while still retaining its capacity to accommodate vehicles.
More Than Just a Crossing: Creating a Thriving Habitat
The transformation involves more than simply adding a few plants. Logs salvaged from recent land clearing at the Mt Ousley interchange have been ingeniously incorporated to create naturalistic pathways. Soon, soil and a diverse array of vegetation will be installed, aiming to replicate the rich biodiversity of a forest floor.
The entire design has been carefully considered to encourage animals to use the bridge as if they were still moving through an unbroken expanse of bushland. “Every bit of the structure has been thought through very carefully,” Ms. Madden explained. “We want everything to use it, from the invertebrates through to swamp wallabies and the wombats, as well as the koalas.”
To cater to arboreal species, elevated structures and ropes will facilitate the movement of gliders and possums above ground. Simultaneously, the ground cover will provide essential protection for smaller animals from potential predators. “There were about four or five different butterflies actually crossing in there already,” Mr. Crombie noted, a promising early sign.
Matthew Burns, Transport for NSW director of regional delivery and statewide services, acknowledged the unique opportunity this project presents for his team. “It is a really great opportunity for our bridge carpenters to work on large timbers and get that experience and exposure to these unique projects,” he said. “It is great to see how the various different parts needed to come together and get the best outcome, and see from a koala’s point of view what makes it attractive… and how they get from one side of the motorway to the other.”
Monitoring the First Steps of Wildlife
To assess the success of this innovative corridor, cameras have been strategically installed. These will be monitored for several years to meticulously track which species return and how they utilise the crossing.
“This is the first retrofit of an existing structure [for use as a wildlife corridor] that we know of in Australia,” Ms. Madden proudly stated. “And I can’t wait to see the first proper crossing of a possum, a wombat or a koala.”
For Bob Crombie, witnessing the realisation of his half-century-old dream is a deeply personal and profoundly rewarding experience. “Look, it feels terrific. I didn’t think I would see it,” he admitted. “What’s being done here is wonderful thinking… recognition of wildlife is important. This is not one, this is only the beginning.” This pioneering project holds the promise of inspiring similar initiatives across Australia, fostering a future where human infrastructure and the natural world can coexist more harmoniously.
