Australian towns and cities are home to more than just humans.
Over thirty percent of threatened species live in urban areas, but one of the greatest problems facing many animals is that places that were once their homes no longer exist.
Urban development destroys habitats, forcing many organisms into smaller or degraded environments that offer poor quality of life and reduced prospects for long-term survival.
The worrying decline in numbers of large old trees around the world, and the resulting loss of hollows that develop in their trunks and branches is a typical example. Tree hollows provide shelter for many birds, mammals, and reptiles.
Unfortunately, these older hollow-bearing trees are becoming rarer in cities. Managers and residents cut them down believing they might fall or drop heavy branches. Replacement trees can take centuries to mature.
There is an urgent need to provide habitat structures that can allow wildlife to thrive in cities, but this is a difficult challenge. For example, one response to the lack of tree hollows is to install artificial hollows like nest boxes. While these boxes can help, they have several shortcomings - they can deteriorate easily and some animals don't like to use them.
In our recent study, we show how computer-aided design and manufacturing can improve the design of artificial hollows, opening new opportunities for restoring animal habitats in urban areas.
Computer-aided design uses software to create 3D models of objects, while computer-aided manufacturing automates their making. These technologies have grown in importance since the 1960s, helping to engineer cars, planes, boats, rocket ships, and buildings.
From laser-cut reefs to 3D-printed seawalls, computers enable creation of complex structures in multiple sites. We show that computer-aided design and manufacturing can produce structures that resemble natural hollows while integrating organic and thermally stable materials. The resulting structures are easy to reproduce, adapt, assemble, and install.
These benefits result from the process we have developed to help designers explore new technologies, materials, and approaches. The process considers the needs of the target species, the people installing the hollows, and other members of local ecosystems including animals and plants.
Recently featured on ABC Catalyst, our project tested these ideas in a pilot that targeted the biggest hollow-dwelling bird to live in Australian cities - the powerful owl (Ninox strenua).
With the aid of computers, we designed hollows that draw inspiration from the natural habitat structures that powerful owls use for nesting - tree cavities and termite nests.
Like tree cavities, our artificial hollows feature rounded entrance pads for landing, tunnels for feeding, and stepped interiors to aid climbing. Like termite nests, they precisely fit the complex geometries of host trees. 3D scanning helps to fit the hollows on branches at positions preferred by owls, and in areas where arborists find installation easier.
We built two types of computationally designed hollows - one made from 3D-printed wood and the other from hempcrete (a building product that is a mix of hemp wood fibres with lime and water). Our assembly process uses augmented-reality headsets that overlay digital guides atop physical models to simplify the assembly using modular components.
We are now in the process of monitoring how these computationally designed hollows perform in comparison with nest boxes and carved logs. We have installed the prototype hollows at sites across Melbourne and equipped them with sensors to collect data on microclimate and habitation. The monitoring will inform our computer models and material selections to improve future designs.
It will take some time to know if computationally designed hollows will attract powerful owls. Targeting these elusive birds is a hugely ambitious goal. Powerful owls are rare, listed as threatened in Victoria, and there has been almost no success in enticing them to use artificial hollows.
Other species, including lorikeets and possums, have shown interest in using our hollows. This is a promising sign for conservationists and land managers who are looking to support local biodiversity or increase the prey base for the owls.
There are exciting opportunities to extend our approach to create more ambitious and effective designs for other sites and species. Future research will explore the use of novel biomaterials that are sustainable, feasible, and suitable for target animals. Possibilities include robotically printed clay, drone-sprayed mud, or 3D-printed aggregations of sticks.
We plan to make future designs publicly accessible through open-source databases that provide do-it-yourself recipes for customisable designs and biodegradable materials.
This work on artificial hollows sits within the broader shift in design practices that increasingly recognise the need for innovative habitat creation. Innovative examples range from environmentally-sensitive lighting and designs that support moss growth on buildings to lightweight tensegrity structures that provide bird roosts on utility poles.
These proposals show how urban areas could look when designers use technologies for ecocentric purposes instead of focusing on solely human goals. They present relevant ideas for architects and others who have declared their commitment to addressing the climate and biodiversity crises.
We hope that innovations that retrofit existing structures or construct new buildings can utilise computer-aided design to present compelling visions for successful coexistence with wildlife in urban environments.
The project shows what is possible when interdisciplinary teams work together on challenging ecological issues. This research is an outcome of a collaboration between the University of Melbourne (Deep Design Lab; Melbourne School of Design; School of Ecosystem and Forest Sciences; School of Biosciences; Grounds and Sustainability), Monash University, Deakin University, Knox City Council, Melbourne Tree Care, and the Hemp Building Company among others.
