Hume Highway nestbox offset: ecological, economic and governance failure

Our new paper in Biological Conservation has been featured in an article on ABC News:

A review of a $200,000 effort to protect animals impacted by a major roadworks project in southern NSW has found its attempts to assist the survival of threatened species have failed.

Researchers spent four years assessing the Southern Hume Highway Duplication project’s effectiveness in helping three species affected by land clearing between Holbrook and Coolac.

Prof David Lindemayer, Maron Crane and the Long Term Ecology Group at the ANU monitored 587 nestboxes which had been installed to offset the clearing of hundreds of old hollow-bearing trees, which provide crucial nesting habitat for a host of threatened critters.  Many of the boxes were specifically designed for three threatened species – the Squirrel Glider, the Superb Parrot and the Brown Treecreeper.

Percentage rates of nest box use by each of the species of conservation concern (denoted nest box use), rates of use of large old hollow-bearing trees from studies outside the areas subject to clearing for highway upgrading (for superb parrot and squirrel glider only) (denoted hollow use), and the proportion of long-term sites where each of the three target species had been recorded between 2010 and 2013 (denoted site occupancy). Data on nest box use excludes boxes with an entrance too small to permit entry of a given species. Source: 

Unfortunately, David and his team found that the nestboxes were rarely used by native wildlife, and instead they were frequently occupied by invasive species such as bees, mice and rats. 10% of the boxes had collapsed, were stolen or otherwise rendered ineffective just 4 years after being installed.

The offset failed to deliver its intended outcome, but most concerning (for me at least) is that it is unlikely the proponent will be asked to rectify the situation. As mentioned in the ABC News article:

“The project to duplicate the Hume Highway, including between Coolac and Holbrook, complied with NSW and Australian Government environmental conditions of approval,” the RMS said in a statement.

One of the report’s co-authors, University of Queensland Postdoctoral Research Fellow Megan Evans, believes the compliance requirement was part of the problem.

“To satisfy the conditions of the offset, the proponent only had to erect the nest boxes even if they completely failed to provide habitat for threatened species,” Ms Evans said.

Sadly, it is routine practice for development conditions to simply specify the action required, rather than the intended ecological outcome – which means that legally, no-one is responsible for the failure of an offset to compensate for impacts to threatened species. This is starting to change with the recent introduction of a Federal Outcomes Based Conditions policy, but at this stage such conditions are voluntary, and there remain hundreds of existing offsets approved under inadequate conditions of approval.


Lindenmayer, D.B., Crane, M., Evans, M.C., Maron, M., Gibbons, P., Bekessy, S., Blanchard, W., 2017. The anatomy of a failed offset. Biological Conservation 210, Part A, 286–292. doi:10.1016/j.biocon.2017.04.022

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

Create a website or blog at