Foxes to blame for fires?

17 Oct, 2010 11:43 AM

THERE are a few things missing from the discussion about forest fire hazard management. Truffles. Bandicoots. And poteroos, bettongs, woylies and a whole suite of small fungi-loving marsupials.

Admittedly, any links between the loss of truffle-hunting marsupials and the ferocity of latter-day native forest fires are only conjecture, but it's an argument that opens up such an interesting world that it's worth exploring for the journey's sake.

The theory goes roughly like this:

Thanks to foxes, and probably cats, today's native forests have only a fraction, if any, of the small fungi-loving marsupials that once used to live in these environments.

These little "rat kangaroos" have two qualities that equip them for fungi-hunting: an extraordinary sense of smell (as biologist Andrew Claridge told me, "A bandicoot is basically a nose on legs") and a great capacity for digging.

Some of these rat-sized creatures scratch out 30-100 little diggings each night in pursuit of fungi. In doing so, they can move anywhere between 0.5 to four tonnes of litter and soil in the course of a year.

Each of these diggings collects drifting organic matter and becomes an entry point for water into the soil. The constant turnover of forest litter accelerates its breakdown into humus, which in turn increases the soil's capacity to hold moisture (and grow truffles).

Put these elements together - moister soils, accelerated litter breakdown, healthier vegetation that is less prone to shedding leaves and branches under moisture stress - and you have a recipe for less intense forest fires.

Sadly, there is little hard scientific evidence for this attractive theory. But it is supported by the observations of a couple of men in a position to speculate.

I was introduced to the idea by Dr Jim Trappe, a legendary American truffle specialist who, despite being retired and nearing eighty, regularly comes to Australia to catalogue our truffle riches. (see breakout)

Dr Trappe outlined how, along with their relationship with trees, many forest truffles have a relationship to the small marsupials that forage for them. The fungi are spread through spores excreted in marsupial pellets.

Andrew Claridge, a senior research scientist with NSW National Parks and Wildlife Service who has for years married his marsupial expertise to Dr Trappe's mastery of fungi, tells me that some mycorrhizae are fire-adapted. After a forest fire their truffles emit a powerful smell of rotting onions or garlic.

"Rotting onions" is barbecued steak to bandicoots and other fungi-lovers: a come-on so powerful that they will be hunting for truffles while the ashes are still cooling.

After the truffle is eaten, its spores are deposited in marsupial pellets across the burned zone, setting up a nutrient delivery network that can aid trees in their recovery from fire.

What does all this mean for fire management? It's complicated.

Unlike open woodlands, where mosaic burning every few years can be beneficial, tall wet forests and the creatures that live there don't respond well to regular fire.

Studies of the long-nosed poteroo suggest that mosaic burning once every 20-30 years is optimal for the species. Dr Trappe adds that truffles need 2-4 centimetres of forest litter to flourish.

In a (hypothetical) functioning forest, where trees, truffles and truffle-eaters are working in concert, regular hazard reduction burning would seem to be a recipe for reducing marsupial numbers, drying out the soil and increasing the amount of un-decomposed litter.

But thanks to the fox, a spanner in the ecological machinery, small marsupials very seldom exist in the numbers to test whether more critters=damper forests=less destructive fires.

Eliminate foxes, Dr Claridge says, and in five-10 years populations of small marsupials begin to rise. (Biologists still aren't certain about how cats fit into the picture.) That's being tried in several areas, notably in east Gippsland.

It's a long-term commitment, and we may not see any change for maybe 25 years. But some day, hopefully, we'll be in a position to know whether ferocious forest fires are somehow the fault of the fox.

* Jim Trappe and Andrew Claridge collaborated with Chris Maser on the book, Trees, Truffles, and Beasts: How Forests Function.

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true greenie
14/11/2010 10:45:20 AM

Unfortunately cats are too dear to some city peoples hearts to acknowledge the damage and ecological upset they cause. Foxes are more limited in their spread across Australia, but cats have invaded all areas; through to the deserts, upsetting the balance where ever they are. More thorough understanding and controll options should be investigated.


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