The $213,000 spent on nest boxes to offset trees lost widening the Hume Highway has been wasted, says a professor of ecology at the Fenner School, Australian National University.
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Professor David Lindenmayer recently led a four-year study to investigate whether nest boxes commissioned by the Roads and Maritime Service were effective hides for the species they were designed to encourage.
When the Hume Highway was widened between Coolac and Holbrook, the nest boxes were installed in the area to offset the loss of established tree hollows which vulnerable species use to nest. “To our horror, we discovered that the species of endangered and threatened animals that the project was targeting weren’t using the boxes at all,” Professor Lindenmayer said.
The boxes sought to attract the superb parrot, squirrel gliders and the brown tree creeper, all vulnerable species. Instead, they were more commonly used by pests, such as rats and starlings.
In just seven of the 3000 checks carried out were squirrel gliders found to be using the boxes, and in only two was the brown tree creeper found. No superb parrots were found during the checks.
Of the 587 boxes installed, seven went missing, presumably stolen, and 14 fell out of the trees. Professor Lindenmayer believes these findings indicate the boxes will be all but useless in 10 years.
Offsets are a common practice in environmental management worldwide. “The loss of these really big trees is a massive problem globally,” Professor Lindenmayer said.
“The loss of these big trees has a disproportionately large effect in Australia, because we have a disproportionately large number of kind of species that are dependent on these big old trees. The discovery here is that an offset, to try to compensate for the loss of these big trees, is simply not effective.”
The study demonstrates the need to invest in effective long-term land management, rather than temporary measures, he said. Working towards establishing large trees not only provides a habitat for vulnerable and endangered species, it can also fix a whole host of agricultural problems. Tree planting sites in unused land, such as gully lines around can improve water quality, decrease erosion and lower salinity by lowering the water table.
“A better offset in this case is likely to be making sure we can regenerate big old trees actually coming through.”