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Enhancing habitat connectivity & biodiversity by use of wooden glide poles

Sugar Glider image credit PXHere
Sugar Glider

Overview of Impact

Roads and highways separate animal populations and disrupt their opportunities to find food and suitable mates. While traditional road crossing structures can overcome these problems, flying mammals (gliders) are reluctant to use them. To help preserve glider populations, Southern Cross University researchers developed wooden ‘glide poles’ that act as stepping stones for gliders to cover distances that would otherwise be too far for them to glide.

This low-cost solution has been used widely around Brisbane, on Australian highways and in the USA, providing economic and environmental benefits to councils, road authorities and developers. Gliders are important for pollination and insect control. Glide poles protect gliders and therefore also benefit ecosystem health and support biodiversity.

  • Local Government
  • Road authorities
  • Property developers
  • Community groups
  • Natural ecosystems

Urbanisation is the primary cause of biodiversity loss world-wide. Roads are particularly problematic as they fragment wildlife habitats and disrupt foraging opportunities and population processes. Isolation can disrupt gene flow resulting in a lack of genetic diversity and potential extinction of local populations. Road crossing structures are used to mitigate the effects of habitat fragmentation on wildlife. Prior to Associate Professor Ross Goldingay’s research in 2002, mitigation measures did not accommodate arboreal mammals (e.g. gliders) that do not use traditional crossing structures. Gliders are highly vulnerable to habitat fragmentation because they are reluctant to cross canopy gaps and have a heightened risk of predation when on the ground.

Loss of glider populations can have a significant impact on ecosystem health. Most gliders feed on nectar and pollen (e.g. 48% feeding time of squirrel gliders is for nectar and pollen), and Professor Goldingay’s research has shown gliders to be as important as birds in pollination. The loss of local populations may lead to adverse changes in outcrossing rates in flowering trees. Furthermore, many gliders feed on leaf-eating insects and loss of gliders may lead to increased herbivory. Both factors can negatively impact forest dynamics. A number of Australian gliders are already threatened including the squirrel glider (endangered Vic, vulnerable NSW/SA), yellow-bellied glider (vulnerable North Qld/NSW/nationally), greater glider (vulnerable nationally), mahogany glider (endangered North Qld/nationally). Population and genetic modelling of glider populations by Professor Goldingay’s team demonstrated that habitat fragmentation disrupts gene flow and may lead to local extinctions, however linking remnant habitats improves viability of populations to ensure survival.

Professor Goldingay proposed an innovative solution to restore connectivity in fragmented glider habitats, recommending the use of tall wooden glide poles to facilitate crossings that exceed gliding ability. His team proved the effectiveness of these ‘stepping stones’ for road crossings and movement between vegetation remnants. Glide poles are now in use at seven Brisbane sites, on the Pacific, Hume, Princes, Oxley and Bruce Highways, and in the USA (northern flying squirrel). This world-first solution delivers not only demonstrable environmental benefits but also economic benefits for local councils, road authorities and developers. A set of glide poles is one third of the cost of a rope bridge (another crossing structure for gliders). Furthermore, poles can be easily retrofitted along existing roads. Since 2002 Professor Goldingay’s team has worked closely with Brisbane City Council across five glide pole installations (Brisbane City Council-funded research 2002-11). Professor Goldingay’s understandings of morphology, gliding behaviour and trigonometry of gliders are reflected in Brisbane City Council’s protocols for glide pole height, design and placement. The Brisbane City Council website describes the Compton Road site (glide poles on a land bridge) where four research projects were conducted by Professor Goldingay’s team as an “invaluable and worthwhile exercise… to protect biodiversity by reconnecting ecological corridors.” Brisbane City Council also used Professor Goldingay’s expertise for policy development. Their Gliders Conservation Action Statement includes 22 citations /17 references to his research. 

The research has also benefitted developers. In 2015-16 Professor Goldingay’s team worked with Urbex Pty Ltd on a proposed new Brisbane public golf course and residential precinct with a resident squirrel glider population. Professor Goldingay’s team conducted a baseline population study and provided glide pole design specifications. Urbex funded a $175,000 PhD scholarship. 

Professor Goldingay’s has expertise benefitted NSW local councils. His team surveyed yellow-bellied gliders and recommended glide poles for Gosford City Council (2010-12). He also worked with Wyong, Cessnock, Great Lakes and Lake Macquarie City Councils on squirrel gliders. Professor Goldingay presented on urban fragmentation and glider genetics (2015) and influenced policy (18 citations in Lake Macquarie Squirrel Glider Planning and Management Guidelines 2015, a document to guide local and State decision-making on development approvals which impact glider populations).

Professor Goldingay and his team provided expert advice to Roads and Maritime Services NSW (RMS) for several new road projects including the Oxley Highway deviation Port Macquarie (2007) and the Princes Highway, Termeil (2012-14). They evaluated the road-crossing potential of gliding mammals and provided glide pole design specifications. Professor Goldingay also monitored use of glide poles at Oxley Highway, Port Macquarie (2013-16) and conducted ecological monitoring of yellow-bellied glider for Pacific Highway (Warrell Creek to Nambucca Heads) (2014). Since 2014, glide poles have been installed at 15 locations on the Pacific Highway between Port Macquarie and Wardell, with more to be installed from Wardell to Ballina. Professor Goldingay’s research has also informed RMS policy and procedures (23 citations/8 references in Threatened Glider Management Plan 2015). Professor Goldingay’s long-term relationship with RMS allowed this authority to create sound policy, integrate positive environmental benefits into road projects, preserve local glider populations and enhance biodiversity of natural ecosystems impacted by road construction.

A 2014 presentation to Australasian Network for Ecology and Transportation on field testing of glider road crossing structures benefitted industry, government (transport, regulatory, planning and environmental agencies), environmental consultants and community groups (environmental and wildlife carers). Professor Goldingay also presented to community organisations (Wildlife Preservation Society of Queensland, Karawatha Forest Protection Society and Bulimba Creek Catchment Coordinating Committee). Professor Goldingay’s novel approach to enhancing habitat connectivity for gliders delivered a cost-effective, environmentally appropriate option for councils, road authorities and developers, but most importantly it offered security to threatened local glider populations, and by extension, preserved biodiversity and ecosystem health.

In 2004 Professor Goldingay and David J Sharpe (SCU) showed squirrel gliders in fragmented habitats, Brisbane, were at risk of extinction. Glide poles were proposed to enable gliding mammals to cross roads. Subsequent modelling of greater gliders and squirrel gliders by Professor Goldingay and Brendan Taylor (SCU) (2009-2012) established that populations could be rescued from extinction by restoration of habitat connectivity. In 2013 Professor Goldingay worked with Harrisson and Taylor (both of Monash University), Ball (of Central Queensland University and Qld Parks & Wildlife, co-supervised by Professor Goldingay) and Sharpe and Taylor (both SCU) to determine that genetic diversity of isolated squirrel glider populations (Brisbane and Mackay) was seriously compromised. Without habitat connectivity being restored, populations would collapse.

Professor Goldingay and Taylor’s 2009 research (squirrel glider, Brisbane) and Professor Goldingay’s 2014 work (yellow-bellied glider, Vic) addressed a knowledge gap about gliding behaviour. They determined length of glides/glide angles, essential information for optimising height of/space between glide poles. Proof of concept (poles would be used by gliders to move between habitat fragments) was undertaken by Ball and Professor Goldingay in 2008 (Mackay). They found that poles facilitated glider movement. In 2011 Professor Goldingay, Taylor and Ball presented evidence of glide pole use (2 Brisbane sites and a Mackay site). In 2012/13 at 3 Brisbane sites and in Tweed, Taylor and Professor Goldingay filmed free glides between poles on a land bridge (1 glide per 3.8 nights) across a two-lane road (16 confirmed crossings) establishing definitively that glide poles enhance habitat connectivity.

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