Koala knows best when it comes to landscape restoration

Mining companies, farmers and developers are often involved in the rehabilitation of native landscapes, but how effective are their efforts? New research suggests that in some parts of Australia, koalas and other native animals may be best placed to adjudicate whether or not rehabilitation has been successful.

As Dr Romane Cristescu of the University of NSW, lead author of the research report, explained, “Rehabilitation of a former mine site is a legal requirement in Australia. The goal is to restore the ecosystem to something as close to its original function as possible, and with the same plant and animal species mix it held before. However, the point at which the restoration can be deemed ‘successful’ is difficult to judge and can be a bit subjective.”

Indeed, the researchers note that “The success of rehabilitation projects, to date, has focused on abiotic and flora-based criteria of success, leaving fauna unmonitored. This follows from the common paradigm that if flora recovers, fauna will recover too.”

Following the restoration of former sandmining sites on North Stradbroke Island, the researchers, the mining company, the government and the local community all agreed that the one animal which should benefit from the restoration was the koala.

“Koalas are in serious decline due to habitat loss in South East Queensland, so it’s important to know whether or not restored areas will support them,” said Cristescu.

So the researchers examined whether the flora criteria used to assess mine site rehabilitation was reflected in the behaviour of koalas. They identified the areas which had been labelled the ‘best restored’ and equipped koalas in the surrounding areas with radio collars. These were used to monitor the animals’ movements, indicating whether they settled into the restored habitat or moved away from it.

“When we compared the areas that were best-rehabilitated according to vegetation criteria with the areas being used by koalas, it quickly became apparent that they seldom matched,” said Cristescu.

“This is a strong signal that the current policies being used to guide mine site rehabilitation do not necessarily ensure successful rehabilitation for all plants and animals.”

Even after the researchers developed their own biologically relevant criteria for the koalas - eg, species richness in food trees, and tree canopy cover - correlations were higher but still inconsistent.

“Koalas were happily recolonising other parts of the rehabilitated areas that ranked lower in terms of vegetation success,” revealed Cristescu.

The report throws up several questions about how the restoration process should be conducted in future. Should one or more species be monitored? How should they be picked? Can the costs of monitoring them be justified? The researchers recommend that the animal(s) of choice should be “species of interest (eg, threatened and charismatic) and … fauna involved in long-term resilience of ecosystems”.

Their research is published in the Journal of Applied Ecology.