Making sure that what we think is good for box-gum woodland restoration, actually is.
Box-gum grassy woodlands were once a widespread and productive ecosystem in south eastern Australia. However, since European settlement we’ve lost (largely through clearing) around 90% of the woodlands. Of what’s left, only around 5% is regarded as being in good condition, although, the description of ‘good’ is a relative term because we simply don’t know how today’s woodlands compare with pre-European woodlands. We do know that most of what is left is degraded and experiencing declining biodiversity.
How do you manage, protect and improve important ecosystems like the box-gum grassy woodlands when you have no benchmarks of what a healthy ecosystem might be? That’s the daunting challenge facing a new collaborative research project between scientists at ANU and the ACT Government which is seeking to determine how to best manage grassy box woodlands on the northern boundary of the Australian Capital Territory – in the Mulligans Flat and Goorooyarroo Nature Reserves.
“We’re looking at ways of improving grass box gum woodlands for biodiversity by setting up various manipulations and treatments in Mulligans Flat and Goorooyarroo reserves,” says Dr Adrian Manning, a Research Fellow at the Fenner School of Environment and Society. Adrian manages research on the project.
“Our treatments include adding dead wood, using controlled burning and excluding kangaroos that are currently over abundant at the site and are having a major impact on the system,” says Dr Manning. “The ACT Government is also going to build a feral-proof fence around one half of the experiment to keep out foxes, cats and dogs. The idea being that we can look at the effects of all these treatments and the interactions between these treatments.”
Conserving box-gum grassy woodlands is not a new issue; it’s one that ecologists and conservationists have been pondering for decades. Adding ‘fallen’ timber, managing fire regimes and controlling grazers and predators all seem like logical things to do. Why do we need to experiment with them?
“The experiments are crucial because we really don’t know how these treatments will work or interact,” says Dr Manning. “And our record of protecting grassy box woodlands isn’t very good.
“So far, conservation efforts have involved fencing out stock, trying to stop people taking out dead wood (usually as firewood) and tree planting. The hope is that fencing out stock might allow tree regeneration but in a lot of cases these ecosystems have changed so much that fencing by itself isn’t enough. Phosphates have been added and exotic understoreys, often grasses, have come in. Which means, in most places, there’s actually been a regime shift. The system has changed so much it’s operating in a different way. It’s not just a case of relaxing those threatening processes and letting the system recover. We know that simply leaving an area alone doesn’t always work.
“One example of this is that we’re still witnessing the disappearance of species from box-gum woodlands, even those placed in a reserve. Mulligan’s Flat, for example, was set aside as a reserve in 1995. At that time it had brown tree creepers, a threatened woodland bird species. Several years after it was declared a reserve it lost its population of brown tree creepers – they’ve become locally extinct in that woodland. And we’re seeing similar things happening in other reserves. So, threatening processes are not being reversed by creating reserves. Therefore there’s a need for proactive conservation, and what we’re trying to do is provide the evidence for how this might be best done in box-gum woodlands.”
The woodlands experiment is unique on a number of scores, including its scale of operation.
“We’re not being half-hearted with our treatments,” says Dr Manning. “It probably hasn’t been approached in such an intense way at one site ever before. For example, with the addition of dead wood we’ve added at least 2000 tonnes of timber, which would make it one of the largest types of experiments like this, at the very least in Australia.
“And working closely with a government partner is another noteworthy aspect of this project. I think and I hope that this project can show the way that researchers and conservation agencies can work together so there’s more of an integration of restoration conservation and research and we get a more evidence-based approach to conservation. And these timber treatments are a good example of this.
“I mean we could just say: ‘fallen timber provides important refuge for small mammals so just add timber’ and not specify how much or in what distributions. But what we want to do is take a bit more of a scientific approach and tease out what works and what doesn’t. So, if you’re going to add timber, let’s test how much you need to get the desired effect and how do you spread it.
“In our experimental design we’re looking at different distributions, clumping or dispersed patterns and mixtures of both. And that’s important because timber is expensive to move so you don’t want to put on any more than you have to.
“I think that’s a good illustration of why it’s important for science to be involved rather than simply saying ‘let’s add more timber’. What we hope to do is to inform that process of restoration and demonstrate the value of such a process.”
The woodland enhancement experiment has many partners. In addition to ANU and the ACT government, there and several researchers from CSIRO Sustainable Ecosystems and CSIRO Entomology, with a variety of PhD and honours students studying different components in the system.
“One of the unique things about this project are the linkages between ourselves, the ACT government and other research institutions,” observes Dr Manning. “The idea is not simply that we are the scientists and they are the government who are doing things for our experiment. Rather, we own the experiment together and we work together to make it happen. What we learn and achieve is shared. It can take longer to set up such a process but I believe the benefits are also more long lived.”