I’m excited to say that the Hermon Slade Foundation has thrown support behind my research for a second consecutive year. Last year it was for a project examining the long-term recovery of woodland bird communities following southern Australia’s Millennium Drought (2001-2009), building on previous work in the region that documented shorter-term responses (see here, here,here, and a perspective piece it inspired here).
This time it is to initiate a study on the capacity for traditional Indigenous fire management to restore mammal communities. The project is in collaboration with Rebecca and Doug Bird from the Human Environmental Dynamics Lab at Penn State, USA, and Euan Ritchie from Deakin University. We will work in remote parts of the Western Desert of Western Australia, where Rebecca and Doug have done ground-breaking work (see here, here, here) on the fire regimes maintained by Indigenous communities and their impacts on native species. We will compare areas under active Indigenous fire management with areas where such management has long ceased to reveal the ecological consequences of an active, traditional fire regime. We are extremely grateful to the Hermon Slade Foundation for supporting this work, and I can’t wait for this collaboration to begin later in the year.
A new paper from PhD student Mark Hall. This is actually Mark’s honours work, so it’s great to see it published (far too few honours theses make it to publication). Well done Mark!
In agricultural regions worldwide, linear networks of vegetation such as hedges, fencerows and live fences provide habitat for plant and animal species in heavily modified landscapes. In Australia, networks of remnant native vegetation along roadsides are a distinctive feature of many rural landscapes. Here, we investigated the richness and composition of woodland-dependent bird communities in networks of eucalypt woodland vegetation along roadsides, in an agricultural region in which >80% of native woodland and forest vegetation has been cleared. We stratified sites in a) cross sections and b) linear strips of roadside vegetation, to test the influence on woodland birds of site location and configuration in the linear network (the ‘intersection effect’). We also examined the influence of tree size at the site, the amount of wooded vegetation surrounding the site, and the abundance of an aggressive native species, the noisy miner Manorina melanocephala. Birds were surveyed at 26 pairs of sites (cross section or linear strip) on four occasions. A total of 66 species was recorded, including 35 woodland species. The richness of woodland bird species was influenced by site configuration, with more species present at cross sections, particularly those with larger trees (>30 cm diameter). However, the strongest influence on species richness was the relative abundance of the noisy miner. The richness of woodland birds at sites where noisy miners were abundant was ~20% of that where miners were absent. These results recognise the value of networks of roadside vegetation as habitat for woodland birds in depleted agricultural landscapes; but highlight that this value is not realised for much of this vast vegetation network because of the dominance of the noisy miner. Nevertheless, roadside vegetation is particularly important where the configuration of networks create nodes that facilitate movement. Globally, the protection, conservation and restoration of such linear networks has an important influence on the persistence of biota within human-dominated landscapes.
I’ve recently been hopeful about a possible revival of landscape-scale research. To me, conservation science went a bit like this: general principles were being established in the 1960; reserves were advocated in the 1970s; reserve planning was perfected in the 80s and 90s; the “matrix” outside protected areas attracted attention in the 1990s, along with a rise in landscape ecology; ecosystem services arose as a new field of enquiry in the 2000s; and protected areas…
Unfortunately, mass coral bleaching is just one example of a far broader problem. Although it represents a rapid and extensive example of ecosystem degradation, coral bleaching is not surprising: it is consistent with many changes that are occurring now across Australia’s natural environments.
Our iconic trees – including the world’s tallest flowering plant, the Mountain Ash, and the most widely distributed eucalypt, the River Red Gum – are among the hardest hit.
A stark example is the floodplain forests of the Murray-Darling Basin. Reduced rainfall and water extraction for human needs have deprived River Red Gums of the flooding integral to their existence. The consequence is that 79% of forests on the Murray River have dieback. Tree graveyards are a common sight.
On the back of historic declines (primarily due to land clearing), two-thirds of species declined substantially as the drought took hold. The assumption, or perhaps hope, was that these declines were part of a natural cycle, and that the drought’s end would bring a return to normal. This did not happen.
The result is that our bird communities have dramatically changed in as little as two decades. As we enter another period of drying, there is grave concern about the future of southern Australia’s birds.
What do Australians value?
These are just a few examples of massive ecosystem degradation. Sadly, there are many more. The battle for Australia’s biodiversity can still be won, but this requires decisive action on climate change and serious investment over many election cycles.
The budget allocation for the federal Department of the Environment is shrinking and is now less than 0.5% of the government’s spending. It is hard not to draw comparisons with the recent announcement that Australia will spend A$50 billion on submarines.
By contrast, avoiding extinctions of Australian birds would cost around A$10 million per year — a cost we are, at the moment, unwilling to meet.
“Don’t tell me what you value; show me your budget, and I’ll tell you what you value.”
On May 3, Australia’s government will present its 2016 budget and, with an election looming, we will also soon learn about the opposition’s spending commitments. The coming months will expose how major parties value Australia’s environment, and the election to follow will measure the degree to which Australians accept it.
Something alarming happened in the woodlands of southern Australia last decade. The birds stopped calling. Well, not entirely, but substantially. The chorus of kookaburras, honeyeaters and babblers that usually make the woodland air burst with song was reduced to a whisper.
When the drought broke spectacularly in 2010 with flooding rains, there was a sense of cautious optimism that the region’s biodiversity might have been offered a reprieve. However, two years after the drought had broken, that optimism turned again to alarm. Monitoring data revealed that although around one quarter of bird species increased following the floods, most species had not recovered. Further still, 14–29% of species (depending on the dataset) continued to decline, despite the drought ending. Promisingly, in our recent paper in Journal of Applied Ecology, we think we have found a hint of a silver lining.
If you read the climate change literature, you may be familiar with the idea of ‘climate refugia’. This concept suggests that some areas are buffered from the impacts of climate change or climatic extremes such as drought. For instance, areas that have relatively high moisture or stable microclimates may offer refuge for species during drought. It follows that these areas should be targeted for protection for conservation, to enhance the capacity of biodiversity to persist during climate change.
The concept provides a sense of agency among conservationists in the face of a looming global disturbance over which we have little control. However, although there is evidence of refugia operating over evolutionary time scales and at continental spatial scales, the evidence that we can create refugia at the scale of conservation management is much scarcer.
Our paper provides that evidence. We found that landscapes with more tree cover on productive soils – such as on riverbanks, stream sides, drainage lines and floodplains, collectively termed ‘riparian vegetation’ – retained a higher proportion of their bird species during the drought.
This means that past land clearing, for agriculture and other human land uses, is likely to have diminished the capacity of bird communities to resist the impacts of drought. This might explain why the drought had such huge effects on the region’s bird fauna. On the other hand, by protecting riparian vegetation, and by revegetating cleared riversides, floodplains and drainage lines, we could enhance the capacity of bird communities to persist during the next big drought. That is, we could build climate refuges.
Although this sounds promising, our results come with an important caveat. When the drought broke, landscapes with less riparian tree cover tended to ‘bounce back’ to a greater extent. That is they were more ‘resilient’. This is largely because these same landscapes had a greater need for recovery, having lost a greater proportion of their species pool during the drought. By contrast, landscapes with more riparian tree cover lost fewer species and so had less of a need for recovery post-drought. Over the duration of the entire drought–flood cycle, these two opposing trends cancelled each other out such that two years after the drought, a similar fraction of the bird community was lost across all landscapes.
What does this mean? In simple terms, riparian vegetation enhances the ability of landscapes to retain bird species during the drought, but does not arrest longer-term declines that may cause ongoing species loss over successive drought events.
This does not diminish the important role of riparian vegetation for bird conservation during drought. Retaining a larger portion of the species pool throughout the landscape means that ecological functions continue, functions critical to ecological and economic systems, such as pollination and insect control.
We also know from previous work in these same landscapes that increasing tree cover of any kind increases the richness of woodland birds. Indeed, the total amount of tree cover in the landscape is the most important influence on the number of woodland bird species that can occur. Adding riparian tree cover to heavily modified landscapes gives huge ‘bang for your buck’ in terms of bird conservation, as productive areas support more species and provide specialised habitat for species that favour riparian vegetation. Finally, other work has revealed that landscapes with more tree cover had more stable bird communities, measured in terms of species turnover, over the duration of the drought.
Combined, these results suggest that maintaining and revegetating riparian areas will provide many benefits to bird conservation. It also has many other benefits, including protecting water quality, enhancing aquatic environments, and creating a visually attractive environment. It’s a ‘win-win’ for sustainable land management and nature conservation.