Preventing wildfires: Effectiveness of fuel treatment in forests
.. thanks, DD, yep, excellent .. i agree with your point that suing for cause can be a bit much sometimes .. you probably know the USA has a bit of a reputation for too much of it and the lawnmower note you made sure seems a case of that .. poor guy .. when a dentist cut my tongue a couple of people here said sue, huh? wha? why? .. so that mentality is seeping in here a bit .. in cases of serious and obvious negligence by corporations or individuals sure, but your point is valid, i think .. i was going to post the first adds separately, then decided to fit them into this one .. the bottom one is a cute/fun/interesting read ..
A 2011 study by the U.S. Forest Service, “Review of Fuel Treatment Effectiveness in Forests and Rangelands and a Case Study from the 2007 Megafires in Central Idaho,” .. http://www.treesearch.fs.fed.us/pubs/37405 .. examines various practices used to manage areas in the “wildland-urban interface,” where fires are mostly likely to affect human life.
The study surveys a variety of past research reports, focusing on forest “fuel treatments,” which typically entail thinning vegetation through cutting, prescribed burning, and the use of animal grazing. The goal is to reduce the intensity of wildfires, limit risk to humans and increase the resiliency of ecosystems. But these programs are expensive, their effectiveness is subject to debate, and the science of forest-fire management continues to evolve.
The study’s findings include:
* Analysis of the 2007 Central Idaho megafire confirms what previous scientific literature had hypothesized, that the most effective treatment was mechanical thinning of trees and brush followed by a controlled surface fire.
* Prescribed burn treatments alone are more limited in their effectiveness, and the benefits diminish over time: “It is difficult to kill most medium-sized trees and many small trees by fire alone. Multiple rounds of prescribed fire are more effective … than single entry treatments.”
* Animal grazing was found to be an effective technique: “The removal of biomass during grazing (particularly heavy grazing) reduces fine fuels and decreases risk of fire occurrence and spread.”
* There appears to be no “magic formula” for all forest area types: “While thinning from below is a common treatment and thresholds in tree density, crown base height, crown bulk density, tree spacing, and other fuel composition descriptors exist for a given stand, there is no general prescription that will work in all or even most stands.”
* More research is required on the question of whether fuel treatments might actually increase the likelihood of intense fires in certain environments. It is “certainly possible for fuel treatments to increase fine fuel temperature and create a micro-climate that favors increased winds and lower relative humidity.”
* A 2009 study found that treatments often fell outside the wildland-urban interface (WUI). The National Fire Plan mandates that 50% of treatments be within the WUI, but the study found that, of 44,000 fuel treatments in the western United States, only 3% were within a WUI and only 8% within 2.5 km of the WUI.
* Some past scholarship has concluded incorrectly that expensive fuel treatment programs are not worth their cost, having only “a mean probability of 2.0% to 7.9% of being encountered by moderate or high severity fire within 20 years following treatment.” However, there is strong evidence that fuel treatments indeed mitigate fire effects.
The tiny marsupials who spend their nights digging for truffles on the forest floor could be holding together ecosystems in ways scientists are only beginning to understand.
TAKING AN EARLY MORNING walk through the scrubby forest in Tasmania's south-east, Professor Chris Johnson from the University of Tasmania can tell if the local bandicoots and bettongs have been hard at work the night before.
These little marsupials, looking a bit like kangaroos in miniature, spend all night digging for dinner on the forest floor. But it is not the foraging pits that these little diggers leave that gives them away, but a lack of crunching dead leaves underfoot.
Johnson, an ecologist with over 30 years experience studying mammals, says that these little critters are so prolific with their digging activities that they can bury large amounts of leaf litter in a single night.
And it is this influence on leaf litter loads that has him suspecting that bandicoots and bettongs, together with other mammals that dig for food or burrow for shelter, can influence how a bushfire burns through a landscape.
"Fires tend to start down on the ground in the dry litter and a fire will spread if the litter layer is continuous," Johnson says.
"These animals are in there digging holes and throwing soil up into heaps and that creates a lot of micro-firebreaks at a very, very small scale. This diminishes the likelihood that a small fire will spread and turn into a large intense fire."
While the actions of digging mammals would do little on those high fire-danger days when catastrophic, high-intensity fires can occur, Johnson believes that overall they can have a significant influence on the patterns of low-intensity fires.
"When you've got those mammals going about their business in the woodland ecosystems, the number of days you have when low intensity fires escalate into high intensity fires is going to be fewer, so on the whole there should be less fire impact."
At the moment the evidence is anecdotal and Johnson is now gathering the data to see if his suspicions are correct. But he says the impact of bettongs and bandicoots on reducing fuel loads are so obvious that anybody could notice the difference — well, that is if they actually had the opportunity to see it.
"Most people can't see it because they've got no experience of it. Very few Australians have ever walked through a woodland that has got the full complement of digging mammals because most of them went locally extinct in the early twentieth century."
It is a sad fact that the last 200 years has seen Australia gain the mantle for the highest rate of mammal extinctions in the world, and those mammal species that dig or burrow are no exception to this statistic.
Of the 29 mammal species that are considered to be diggers, six are known to be extinct and a further seven species are endangered. Another five species are vulnerable or near threatened, while most of the remaining species have suffered huge restrictions in their range.
Truffle hunters
But it is only now that scientists are discovering just how important these animals are to Australian ecosystems — and their benefits are not just limited to influencing the way a fire burns.
According to Dr Mathew McDowell, a post-doctoral researcher with Flinders University, so significant are the large-scale losses of these animals that it could jeopardise the survival of whole ecosystems. It is a concept he calls 'extinction debt'.
"When we lose those burrowing and digging animals the effect is of such an impact that probably all of the other species within the area are in trouble... thirty to fifty years down the track they may just suddenly disappear as well."
It is this situation that Professor Giles Hardy and Associate Professor Trish Fleming are hoping does not eventuate in the renowned Jarrah and Wandoo forests in Western Australia's south-west.
Hardy and Fleming, both from Murdoch University's Centre of Excellence for Climate Change, Woodland and Forest Health .. http://www.foresthealth.com.au/ , have been examining the impact of the losses of once-common digging mammals such as boodies and woylies on the health of the forests. And they are seeing some alarming results.
"In certain parts of these forests we are losing trees of all age classes and a lot of trees have changed quite significantly in canopy structure and health, with a quarter to an eighth of the canopy of a healthy tree," explains Hardy.
"When we start to tie all these aspects together, we start to see there is a potential link between tree declines and native mammal loss."
And that link comes in the form of a symbiotic relationship between the roots of the trees and native Australian truffles.
The special type of fungi, known as mycorrhiza, helps the trees gain greater access to water and nutrients. They are spread about the forest floor by mammals that dig up and eat the truffles. With less digging mammals around, the fungi do not spread as readily and the trees become more susceptible to stress.
"Trees with no or fewer mycorrhizal fungi are much more susceptible to diseases because the fungal sheaths that cover the roots provide a lot of protection," Hardy says.
"Also trees with mycorrhizal fungi are much more resilient to drought-stress because the fungi explore much more soil than a root does &mdsh; many thousands times more than what a root can do — so they can source a lot more water and nutrients."
Fleming adds that by digging into the soil the mammals also have a positive effect on soil quality, which would also benefit the trees.
"When they dig, these mammals turn over the soil and change the composition of the soil. They also affect the nature of the soil. Mammal diggings form indentations in hydrophobic soils (where water just runs off) and so increase water infiltration."
But where numbers of digging mammals have dropped away, the abundance of rabbits has dramatically risen. And rabbits dig as well, so why aren't we seeing the same benefits to ecosystem health conferred by them?
It all comes down to the way they dig, according to Professor David Eldridge from the University of New South Wales.
"Rabbits dig pits that are a lot smaller, they are a lot shallower, and they don't last as long. They are not digging enough of them, they are not digging them deep enough, and they are not digging them the right way."
Interestingly, Eldridge has found that rabbit diggings are associated with a greater number of exotic plants, whereas those of bilbies and bettongs favour locally native plants. Seeds are also easier for ants to take from rabbit pits, meaning they are eaten before the have a chance to sprout.
But Eldridge also points out that it is not just mammals that dig. Some reptiles and birds, such as goannas and bush turkeys, also dig, and these animals are likely to also play an important role in maintaining our ecosystems as well.
Whether or not they can be a replacement for the large numbers of digging mammals we have already lost, however, is another story.
For Professor Johnson, it all provides a compelling case for greater control of feral cats and foxes, which continue to be the biggest threat to the dwindling numbers of digging mammals that remain.
Until then, however, your best bet for seeing the grand work of Australia's little diggers on mainland Australia may just be from behind a predator-exclusion fence.
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