Published: 30 January 2013

Improving road safety for Australia’s high-flyers

Ross Goldingay and Brendan Taylor

Roads pose many risks to wildlife – from preventing or curtailing their movement, to causing death or serious injury. Genetic evidence warns us that in many areas, these risks could lead to the local extinction of many species. Given the number of major roads being built or enlarged as road authorities try to accommodate ever-increasing volumes of traffic, the problem of wildlife on roads is set to worsen.

A squirrel glider ascending a roadside ‘glide’ pole installed by Brisbane City Council at Scrub Road.

Credit: B Taylor/R Goldingay

In addition to limiting wildlife movement, roads exact a dreadful toll in the form of road kill. In south-east Queensland, for example, hundreds of koalas are killed on roads each year; in north-east New South Wales, the figure is around 50 koalas per year.

In the leafier suburbs of Sydney, hundreds of common ringtail possums and common brushtail possums are killed on roads each year. The death or injury of these animals is a serious animal welfare issue that is largely unrecognised by anyone other than the innumerable wildlife carers and pro bono working vets who tend to these animals.

But, koalas and possums are just a few of the animals flattened on our roads each year. Many other species are on the list, including several species of endangered frog. So, what can we do about it?

Artificial structures designed to help animals cross under or over roads are becoming more common. Under-road structures range from modified drainage culverts to large, dedicated wildlife underpasses. Over-road structures include various kinds of land bridges that range from 10–800 metres wide and are covered in vegetation. Land bridges are common in Europe, where they enable large mammals, such as deer, to cross highways and prevent serious traffic accidents. Australia has three such structures in New South Wales and three in Queensland, including one just south of Brisbane. But, at a cost of more than AU$1 million, these structures are expensive, leading many to question their relative benefit.

Arboreal mammals are not well served by underpasses and land bridges. While some species may be reluctant to come down to the ground, others – such as koalas and possums – may not be fast enough to avoid ending up as road kill when crossing roads on the ground. In recent years, two new road-crossing structures have been installed for this wildlife group: canopy rope bridges for climbing species, and tall wooden poles for gliding species.

Design of the roadside glide poles installed by Brisbane City Council at Scrub Road.

Credit: B Taylor/R Goldingay

Canopy rope bridges were first trialled in North Queensland by Nigel Weston and his colleagues from James Cook University. They found that all three rainforest ringtail possum species they hoped would use their rope bridges did so, as well as six other mammal species, including Lumholtz’s tree kangaroo. In New South Wales, we have detected five species of arboreal mammal – including three gliding species – on rope bridges that span the Pacific Highway.

We recently published studies describing the success of tall wooden poles in helping squirrel gliders cross roads. In one study, glide poles were installed across two wildlife land bridges in Brisbane. Using motion-activated infra-red cameras, we observed squirrel gliders crossing the land bridge, and therefore the road, at one location once every four nights.

The glide poles on the second land bridge were connected by a rope to form a rudimentary rope bridge. Our camera monitoring revealed that squirrel gliders and ringtail possums used the rope to cross the road about once a week, with brushtail possums crossing once every two weeks.

When we investigated two vegetated land bridges in New South Wales that did not have tall wooden poles, we found no evidence that gliders (in this case, sugar gliders) used the vegetation to move across the bridges.

Discovering that squirrel gliders will cross a road using glide poles installed on a land bridge is important. But, will they use roadside glide poles to glide directly across a road?

To answer this question, Brisbane City Council installed roadside glide poles on a new section of road south of the city. Eleven months of monitoring with cameras provided us with crucial evidence that squirrel gliders regularly used the poles to cross the road.

Future research will focus on whether other gliding mammal species will use similar poles across a range of locations. For example, glide poles are now being incorporated in many new road projects, from the Oxley Highway at Port Macquarie – where 25-metre-high poles have been installed for the vulnerable yellow-bellied glider – to the Hume Highway, south of Canberra, where poles have been installed for squirrel gliders. Poles have also been installed for the endangered mahogany glider in North Queensland.

Over-road glide poles and rope ‘bridges’ – such as this one being used by a brushtail possum – can be built at a fraction of the cost of wildlife underpasses and land-bridges.

Credit: B Taylor/R Goldingay

The good news is that the cost of these structures for arboreal mammals comes at a fraction of the cost of underpasses and land-bridges. Plus, installation can happen at any time during or after road construction. Consequently, we recommend that glide poles be retrofitted across existing roads wherever a need is identified.

For example, we recently conducted simulation modelling of a local squirrel glider population that has been fragmented by the Logan and Gateway Motorways south-west of Brisbane. The results revealed the local population is likely to become extinct without structures to help them cross these major roads. Thus, retrofitting of crossing structures will be critical to the survival of squirrel gliders in this landscape.

Although further research is required to improve the design and installation of rope bridges and glide poles, recent evidence of their value should lead to their wider deployment, including along existing roads.

Dr Ross Goldingay is Associate Professor in the School of Environment, Science & Engineering at Southern Cross University, and is currently the editor of Australian Mammalogy, the journal of the Australian Mammal Society. Dr Brendan Taylor is a post-doctoral fellow in the School of Environment, Science & Engineering at Southern Cross University. Ross and Brendan have been studying road impacts on wildlife and their mitigation for more than 10 years.

More information

Goldingay RL, Rohweder D and Taylor BD (in press). Will arboreal mammals use rope-bridges across a highway in eastern Australia? Australian Mammalogy (online early)

Taylor BD and Goldingay RL (in press). Squirrel gliders use road-side glide poles to cross a road gap. Australian Mammalogy (online early)

Taylor BD and Goldingay RL (2012). Restoring connectivity in landscapes fragmented by major roads: a case study using wooden poles as ‘stepping-stones’ for gliding mammals. Restoration Ecology 20, 671–678.

Weston N, Goosem M, Marsh H, Cohen M and Wilson R (2011). Using canopy bridges to link habitat for arboreal mammals: successful trials in the wet tropics of Queensland. Australian Mammalogy 33, 93–105.

Published: 17 January 2013

Crunch time for metals recycling?

Alex Serpo

With the world facing a rare-earth metals crisis, a paper published in the leading journal Science last year examined how far we are from cradle-to-cradle metal recycling, and identified future constraints and opportunities.

End-of-life recycling rates for commonly used metals such as iron, copper, zinc and lead are above 50 per cent. However, rare earths and other lesser known metals are seldom, if ever, recycled.

Credit: © rihardzz/istockphoto

In the paper, ‘Challenges in metal recycling’ written by US researcher, Barbara Reck, the author identifies a modern paradigm shift in metals use – today, humans exploit virtually every stable element in the periodic table.

In other words, we are now capitalising on every element’s unique physical and chemical properties, whereas for most of human history, we utilised only a handful of metals.

Another modern shift is that of recycling, a ubiquitous aspect of modern life. ‘The generation between 20 and 30 are now the first generation to have grown up with recycling bins as part of normal life,’ writes Reck from Yale University's Center for Industrial Ecology.

Reck adds, however, that the extent of modern metals recycling is well below potential.

'Metals are infinitely recyclable in principle. But in practice, recycling is often inefficient or essentially nonexistent because of limits imposed by social behaviour, product design, recycling technologies, and the thermodynamics of separation.'

She identifies two metrics that provide the most accurate measures of the rate of metals recycling – 'recycled content' and 'end-of-life recycling rate'.

Recycled content describes the share of scrap in metal production, which is important to get a sense of the magnitude of secondary supply. End-of-life recycling rate, on the other hand, is defined as the fraction of metal in discarded products that is reused in such a way as to retain its functional properties.

The paper makes reference to a United Nations’ panel that recently defined and quantified recycling rates for 60 elements. Two key trends are clear from this research.

The first is that end-of-life recycling rates for the commonly used base metals such as iron, copper, zinc and lead are above 50 per cent.

The second trend is that many trace elements are seldom, if ever, recycled. Most of these trace elements are increasingly used in small amounts for very precise technological purposes, such as red phosphors, high-strength magnets, thin-film solar cells, and computer chips.

In those applications, often involving highly comingled 'specialty metals', recovery can be so technologically and economically challenging that the attempt to recycle is seldom made.

'After millennia of products made almost entirely of a handful of metals, modern technology is today using almost every possible metal, but often only once. Few approaches could be more unsustainable,’ comments Reck.

Greater opportunities for collecting used metals have improved recycling rates over recent decades.

Credit: Bidgee under CC-BY-SA-3.0 via Wikimedia Commons

In her paper, Recki identifies lead as a notable exception : '...80 per cent of today’s lead use is for batteries in automobiles and for backup power supplies, and collection and pre-processing rates from these uses are estimated to be within 90–95 per cent as a result of stringent regulation worldwide. The result is a nearly closed-loop system for lead use in batteries.'

While improved product design and enhanced deployment of modern recycling methodology will both improve recycling rates, Reck identifies one activity that stands out as the key to increasing recovery.

'It seems mundane at first telling, but the activity with the greatest potential to improve metal recycling is collection,' she writes. 'Much improvement is possible, but limitations of many kinds – not all of them technological – will preclude complete closure of the materials cycle.'

Reck also identifies a perverse incentive when it comes to product design for recycling: the more advanced and highly engineered the product, the more difficult it is to recycle. This is particularly true for electronics products, but also applies to other goods like cars, aeroplanes and whitegoods.

Collectively, today’s high-tech products make use of almost every metal, in contrast to earlier products that used only a handful of the more common metals.

The paper identifies another paradox of modern materials recovery. 'It is not much of an exaggeration to say that we manufacture modern products with the best possible technologies we can devise, but generally recycle them with relatively basic approaches.

'It is unfortunate from a materials perspective that, for reasons of scale and economics, often only the more basic technologies (shredding, crushing, magnetic sorting) are routinely applied, whereas more advanced technologies (such as laser, near-infrared, or x-ray sorting) are limited to selected recyclate streams.'

The paper dismisses the common notions of infinite recyclability for bulk recycling of common metals.

'Markov chain modelling shows that a unit of the common metals iron, copper, or nickel is only reused two or three times before being lost, gainsaying the notion of metals being repeatedly recyclable.'

Reck’s concluding comments identify how materials substitution could help improve the sustainability of metals supplies.

'Sometimes, scarce metals can be replaced by more common metals with only modest loss of product performance. Examples are aluminum-doped zinc oxides substituting for indium tin oxides in liquid crystal.’

This is a lightly edited version of an article that first appeared in Business Environment Network (BEN) and is reproduced with permission.

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