#invasive trees

Jerry's at Salvin Creek Park in inner Brisbane. It’s an important bushland reserve, home to remnant vegetation communities, eucalyptus forest and local wildlife. Being just 7km from the CBD, and fringed on all sides by suburbia, the reserve faces a lot of different pressures. One of these pressures is weeds. We’re here to find out how one weed, in particular, is being creatively reused to create an invaluable habitat resource for our native animals.

Stefan Hattingh is an ecologist at Bulimba Creek Catchment Coordinating Committee, who help care for the site. He says invasive camphor laurel trees are a big problem. “They were planted in Brisbane because they make amazing wood. Now they’re all over Brisbane because the berries are spread by birds. Particularly in creek lines and gullies.”

Native to Asia, camphor laurel (Cinnamomum camphora) is a large, rapidly growing tree to 30 metres in size. It’s become a widespread problem in both NSW and Qld, where it’s a declared noxious weed. You can tell you’re dealing with camphors as the leaves have a signature scent when crushed; the tree exudes an oil to prevent insect attack.

Stefan says part of the reason they’re such a bad weed is they’re allelopathic, meaning they deploy chemicals to stop other plants growing around them. “You will see around them nothing is growing. Even the falling leaves will smother and kill small plants. They’re very invasive. About the only thing that can use them is birds, who spread the seeds.”

Stefan says removing the camphors is a big undertaking. “Normally we cut them down and chip them into mulch.” For a 20 metre tree, this isn’t a small job. “The footprint and cost to remove them, it’s a lot.”

Steve Collom is an arborist, and specialises in what he calls “conservation arboriculture.” “I’ve always had a passion for conservation.” His work has seen him become the go-to for creating “habitat trees”; carving out nesting hollows for animals in the wood of dead or compromised trees that would otherwise be sent to the chipper. “Overall we’ve done over 2500 carved hollows.”

“300 species of fauna rely on hollows in Australia. But we don’t have any species that can create their own hollows. We tend to rapidly remove and prune any trees that would be reaching hollow bearing potential. It creates a high demand for hollows in these species. The most perfect, picturesque tree in terms of form is often the most barren-nothing can use it. The reasons a tree will fail in some way in the environment, is to produce hollows.”

Natural hollows can take hundreds of years to form, but Steve describes his work as “fast-forwarding this process, you go from several hundred years to 30 minutes.”

Steve has now installed over 10 nesting hollows into camphor laurels at White’s Hill, and they’re being closely monitored for any tenants.

The trees are ringbarked at the base to kill them, and then the canopy is reduced heavily for safety; to stop large limbs breaking off. Sections of trunk are carved out, hollowed and screwed back onto the tree, forming a lid over an internal cavity perfect for a first owner looking to dip their toes in the market.

Steve has built three different kinds of hollows at the site, catering to three different demographics; small parrots, gliders, and microbats. “The internal shape of the hollow is key, and the entrance dimension decides what can get in there.”

Steve and Stefan will continue to monitor the new homes with wildlife cameras to see who moves in. “Usually we remove hollows, or the potential for hollows with a quick blip with the chainsaw. This is a way of reworking that” says Steve. Stefan says he’s thrilled with the job Steve’s done. “He’s turned a problem tree into a real resource.”

Featured Invasive Species:

CAMPHOR LAUREL - Cinnamomum camphora