Rethinking burning for biodiversity

Rethinking burning for biodiversity

Let’s say you’re given a fire-responsive ecosystem. Forest, grassland, shrubland, take your pick – the fire regime is yours to manage. Each ecosystem is a complex network of fire-sensitive plants and animals, and much like a difficult constituency, some species will want one thing (say, long-established, unburnt trees with a moist and shady understorey) and others will want something altogether different (maybe to either grow or scavenge in the newly-opened canopy soon after a fire) With the fire regime at your mercy, how do you keep the voters happy?

Improving the state of biodiversity in Australia is imperative. Over the last 200 years, we have seen the extinction of 29 of 315 land-dwelling mammals. While land degradation, deforestation and invasive species are some of the major drivers of this tragic loss, a growing trend of increasingly intense, frequent and widespread wildfires plays a proportionately threatening role for our native plants and animals. In Australia, fire is one of the strongest natural drivers of ecological change. Management of bushfire regimes through planned burning therefore represents an opportunity to deliver positive outcomes for fire-sensitive plants and animals – if we can get it right.

One common approach to maintaining biodiversity in fire-dependent ecosystems is to maintain a patchwork of ‘mosaics’, where each mosaic contains vegetation which has been burnt more or less recently than the one beside it. For example, some mosaics will be recently burnt, others long unburnt, and some in-between. This approach to fire management, sometimes called pyrodiversity, assumes that fauna will find their appropriate niche among the patchwork, and therefore a diversity of species in the ecosystem will be supported. It is thought that producing this ‘heterogeneity’ in fire-prone landscapes is the best way to protect native plants and animals, under the assumption that pyrodiversity-begets-biodiversity.

This assumption, however, is not necessarily true. This approach has had success in supporting the diversity of a number of certain species globally, including pollinators in North America mixed-conifer forests, and also birds in Australian temperate forests. However, the success of this approach is by no means universal.

Studies in the Murray Mallee in south-eastern Australia – a dry, fire-prone landscape – show that the number of bird species was not associated with heterogeneity in the landscape created by managed fire regimes. Instead, these birds relied heavily upon older vegetation, making this type of vegetation disproportionately important for these species.

Species like the Golden Whistler are some of the last to appear in revegetated bushland after a fire, preferring open canopy vegetation.
Species like the Golden Whistler are some of the last to appear in revegetated bushland after a fire, requiring mature understorey vegetation. Image: Greg Miles via Flickr. Used under [CC BY-SA 2.0]
In this case, the blanket ‘fire-mosaic’ approach to pyrodiversity, in failing to take into account the particular importance of this vegetation type, places the sought-after old vegetation at risk. This fire regime could then in fact be threatening species diversity in this region, instead of nurturing it.

A common argument for the pyrodiversity approach is that it mimics traditional burning practices by Indigenous Australians. This is true in some contexts, though some argue that differences in the modern methods may be giving inferior results. Regardless, identifying exactly where the approach fits and where it does not is critical to protecting biodiversity. So how can we find the best management approach for each landscape? How can we identify the seasonality, regularity, intensity — in short, the fire regime — that a landscape requires? The answer, naturally, is by listening to the plants and animals themselves.

Luckily for us, some very dedicated people are doing just that, by way of volunteer-driven wildlife monitoring projects. Wildlife monitoring can be time-intensive and costly, making it tricky for decision-makers to gather data on faunal responses to fire across study sites at the landscape scale. Tricky, but not impossible. The VNPA’s community-based Caught on Camera project is picking up the slack for the rest of us. Groups of volunteers committed to their local landscape – in this case, Wombat State Forest in central-west Victoria and Bunyip State Park in eastern Victoria – are currently gathering high-quality wildlife monitoring data tracking how animals respond to bushfire in their forest.

Unlike the Golden Whistler, the Flame Robin (a resident species of Wombat State Forest) prefers open vegetation and often appears early after a fire, only to disappear later as the vegetation closes up.
Unlike the Golden Whistler, the Flame Robin (a resident species of Wombat State Forest) prefers open vegetation and often appears early after a fire, only to disappear later as the vegetation closes up. Image: Lachlan Walsh

Their project, running over ten years, will be critical in delivering data to scientists and decision-makers on how animals respond to fire across a whole landscape at an individual species level. Projects such as this one provide contemporary, long-term data that would otherwise be unavailable to environmental decision-makers. Fire managers will be able to use this information to make informed decisions about planned burns which are more nuanced than ‘rules of thumb’ approaches such as the pyrodiversity-begets-biodiversity hypothesis.

While fire management is essential to preserving biodiversity in Australia and trying to prevent increasingly intense large-scale fires, we have to take care to avoid complacency in applying generalistic approaches. Plants and animals can tell us what they need if we listen, and to our collective relief, there are passionate individuals out there who are all ears.

 

 


Banner image courtesy of Tim Brown

 

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