Contrary to common belief, some forests get more fire-resistant with age


Philip Zylstra, University of Wollongong

An out-of-season bushfire raged through Sydney’s southwest at the weekend, burning more than 2,400 hectares and threatening homes.

As the fire season extends and heatwaves become more frequent, it’s vital to preserve our natural protections. My research, recently released in the journal Austral Ecology, contradict one of the central assumptions in Australian fire management – that forest accumulate fuel over time and become increasingly flammable.




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I looked at every fire in every forest in the Australian Alps National Parks and found that mature forests are dramatically less likely to burn. Perhaps surprisingly, once a forest is several decades old it becomes one of our best defences against large bushfires.

The English approach

Within decades of the first graziers taking land in the Australian Alps, observers noticed that English-style management had unintended consequences for an Australian landscape.

In the British Isles, grazing rangelands had been created in the moors by regular burning over thousands of years, and this approach was imported wholesale to Australia’s mountains.

By 1893, however, the botanist Richard Helms had observed that as little as a year after fires were introduced to clear the land, “the scrub and underwood spring up more densely than ever”.

It’s true that, as in the rest of the country, many shrubs in the Alps are germinated by fire. However, the Alps also lie in a climatic zone where many trees are easily killed by fire. As a result, fire produces dense regrowth, and in the worst cases, removes the forest canopy that is essential to maintaining a still, moist micro-climate. Fires burning in this regrowth have abundant dry fuel, and they are exposed to the full strength of the wind.




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Theoretically, that should make regrowth more flammable than old growth, but it is at odds with the widespread assumption that fuels accumulate over time to make old forests the most flammable. Which is the case then? Are old forests more or less flammable than regrowth?

36 million case studies

Looking back over 58 years of mapped fires in the 12 national parks and reserves that make up the Australian Alps National Parks, I asked a simple question: when a wildfire burnt the mountains, did it favour one age of forest over another? If there were equal amounts of forest burnt say, five years, 10 years or 50 years ago, did fires on average burn more in one of those ages than another?

It’s not an entirely new question; people have often studied what happened when a fire crossed into recently burnt areas.

However, instead of just looking at part of a fire, I looked at every hectare it had burnt as separate case study. Instead of only looking at recent fires, I looked at every recorded fire in every forest across the Australian Alps National Parks. Instead of a handful of case studies, I now had 36 million of them.

Consistent with all of the other studies, I found that forests became more flammable in the years after they were burnt; but this is where the similarity ended. Rather than stop there as the other studies have done, I pushed past this line and found something striking. Regardless of which forest I examined, it became dramatically less likely to burn when it matured after 14 to 28 years.

Alpine Ash forests become increasingly flammable until the trees are tall enough to avoid ignition, and the shrubs thin out.
Phil Zylstra, Author provided

The most marked response of these was in the tall, wet Ash forests. These have been unlikely to burn for about three years after a fire, but then the regrowth comes in. Until these trees are about 21 years old, Ash forests are one of the most flammable parts of the mountains, but after this, their flammability drops markedly. When our old Ash forest is burnt, it is condemned to two decades in which it is more than eight times as flammable.

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The forests across the Alps have survived by constructing communities that keep fires small; but their defences are being broken down in the hotter, drier climate we are creating. Roughly the same area of the Victorian Alps was burnt by wildfire in the 10 years from 2003-2014 as had been burnt in the previous 50 years.




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More fire means more flammable forests, which in turn mean more fire; it’s a positive feedback that can accelerate until fire-sensitive ecosystems such as the Ash collapse into permanently more flammable shrublands. Knowing this, however, gives us tools.

The ConversationOld forests are assets to be protected, and priority can be given to nursing older regrowth into its mature stages. It may be the eleventh hour, but we’re better placed now to stand with the forests and add what we can to their fight to survive climate change.

Philip Zylstra, Research Fellow, flammability and fire behaviour, University of Wollongong

This article was originally published on The Conversation. Read the original article.

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What children can teach us about looking after the environment



File 20180413 570 1705drz.jpg?ixlib=rb 1.1
6-year-olds have the social skills to cooperatively overcome the competition of a resource dilemma.
from www.shutterstock.com

Rebecca Koomen, Max Planck Institute

United States President Donald Trump sparked outrage last year when he announced that the US would pull out of the Paris climate agreement. The decision frustrated world leaders because it undermined the process of global cooperation, setting a bad precedent for future agreements to unify countries in the effort to avoid climate disaster.

This is an example of a very common social dilemma, called a common-pool resource (CPR) dilemma. When a natural resource is open access, such as fish in a lake, everyone has to limit the amount they take individually in order to sustain the resource over the long term.

But if some people don’t cooperate, for example by overfishing or pulling out of a global climate agreement, they risk collapsing the resource for everyone else, leading others to follow suit.

Our research, published today in Nature Human Behaviour, found that some six-year-old children are capable of cooperating to sustain a CPR dilemma using strategies resembling those of the most successful real-world solutions by adults.

From tragedy to hope

Back in the 1960s, economists believed this type of environmental dilemma to be unsolvable, famously labelling these competitive traps as the tragedy of the commons.




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More recent work by Nobel laureate Elinor Ostrom tells us that we do actually have the social skills necessary to cooperate and avoid environmental tragedy, when we can communicate and come to fair agreements about how a resource should be divided.

If we fail to find cooperative solutions to these dilemmas, we risk facing disastrous environmental outcomes. Understanding our behaviour and the conditions that are most likely to lead to cooperation could better prepare us to create solutions in the future.

For this reason, myself and my colleague, Esther Herrmann, at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, recently set out to explore the roots of human behaviour in CPR dilemmas.

We looked at how children deal with such a dilemma in the laboratory in order to find out if these basic social skills are already present in developing children. Because children are not yet exposed to as much environmental information as adults, we asked: are children are able to spontaneously use these skills in a novel context to avoid resource collapse?

A magic water game

To test the social behaviour of pairs of six-year-olds in a CPR dilemma, we created an apparatus that mimicked a renewing, but collapsible common-pool resource, “magic water”. The water was slowly pumped from a clear container at the top of the apparatus into a clear cylinder, where it became accessible to the kids for the taking.

Each child and their partner had a clear box in front of them with a set of buoyant eggs inside. They used the magic water to float eggs to the top of the boxes and could then trade their raised eggs for candies at the end of the game. To collect magic water, children could turn an individual water tap on and off whenever they pleased throughout the game, which looked like this:

This image shows a pair of kids playing the common-pool magic water game. Each child could use the magic water to collect eggs they could exchange for candies, but if either one or both took too much water at any given time, they risked collapsing the resource. In order to get the most magic water possible, kids had to work together to sustain it, much like a real-world environmental dilemma.

There was a trick to it though: If either one or both children took too much water at any given time, they risked collapsing the resource which meant no one could get any more. To produce resource collapse, we put a bright red cork into the cylinder where children harvested their magic water. When this cork fell with the water level to a red threshold near the bottom of the cylinder, a magnet mechanism engaged, pulling out a plug at the bottom of the cylinder, dumping all the magic water into a bucket below, out of reach of the children.

Although kids were much more successful at sustaining the magic water when they had their own independent source – instead of a shared (open access) source – about 40% of pairs did find a way to sustain the magic water together. This means partners collapsed the water in the majority of trials, earning fewer candies because they succumbed to the competition of the game. As we know from research with adults in CPR dilemmas, success is far from guaranteed, owing to the competitive nature of this type of dilemma. But, the number of children who did manage to sustain the water shows these skills develop early. Our challenge will be to find ways of fostering these successful behaviours.

For the pairs who managed to avoid resource collapse, some social patterns emerged, and interestingly, these patterns resemble the successful strategies used by adults in real-world CPR dilemmas.

Children’s strategies resemble those of successful adults

One pattern to emerge was a series of verbal rules many of the kids spontaneously came up with and enforced on each other.

The most successful pairs were the ones that made inclusive rules that applied equally to both partners – like “now we both wait until the water rises and then we’ll both take a tiny bit!” – rather than the unilateral rules made up to benefit a dominant child, enforced at the expense of his or her partner.

Systems of rules generated, monitored and enforced by local communities are also some of the most effective strategies for adults in real-world and laboratory CPR dilemmas. For example, many lobster fishing communities in Maine have developed local systems of mapping fishing territories throughout their accessible waters which determine who is allowed to fish where, and when.




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Another pattern evident in the successful sustainers’ behaviour was a tendency for partners to have similar or equal numbers of eggs at the end of the game. In fact, partners who collected more unequal amounts of eggs tended to collapse the magic water more quickly.

This is a pattern also seen in experiments with adults – we fare better when we can establish fair resource access and equitable risk management among stakeholders.

The ConversationOf course, determining what is fair in the global effort to curb the effects of climate change is more complex than a face-to-face game of common-pool magic water. But this work shows that the basic social building blocks needed to avert the tragedy of the commons develop and can be applied early.

Rebecca Koomen, Postdoc, Max Planck Institute

This article was originally published on The Conversation. Read the original article.