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Nature’s pyrotechnics: Fire starters - Of the trees that burn and those that don’t

It’s pointless thinking we can stop wildfires entirely. So, here’s why some trees burn, and some survive, and how to benefit from plants that don’t burn.

Nature’s pyrotechnics: Fire starters - Of the trees that burn and those that don’t
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Fire fighters battle a fire near the town of Hout Bay, South Africa

Chennai

From Siberia to Sumatra, from the Greek and Portuguese islands to the Amazon — in fact, anywhere, where there are trees, shrubs, or grassland, it’s all prone to burn. Some of it even needs to burn to reseed the land and rejuvenate. Some trees, like eucalypts, have adapted to fire over millions of years. Eucalypts burn fast but they know how to survive as well. Others, meanwhile, “wouldn’t burn if you put a blowtorch on them,” says Bob Scholes, a professor of systems ecology at the University of Witwatersrand in South Africa.

These days we tend to think only of two major regions that burn regularly: eastern and southern Australia, and California, where massive, uncontrollable blazes burn eucalypts and pine trees, respectively, with high-intensity, sometimes for months.

But there are fires in Europe, rainforests in Indonesia, and Africa, too. Africa is “the number one hotspot” Some Earth observation maps will suggest that Australia and the western USA don’t burn half as often as parts of Africa, such as central Africa, Angola and the Democratic Republic of Congo. “Africa is known as the ‘fiery continent,’” says Scholes. “If you measure by area-burned, rather than by emissions, Africa has the largest area-burned in the world.” But almost all of those areas are savannas, where relatively low-intensity fires only burn the grass layer, without consuming any of the tree layers above.

“There are specific ecosystems in Africa which have fire behaviours like those in Australia and California, but they are not extensive,” says Scholes. As a result, “no one really worries about (grassland fires) too much,” adds Owen Price, director of the Centre for Environmental Risk Management of Bushfires at the University of Wollongong in Australia. But South Africa is “probably the number one hotspot,” he says. “The savannas are seasonally dry and some of those areas will burn every year,” says Price. “We have the same in northern Australia. They burn frequently, but they are not so intense because they are only burning the grass.”

So, there is a difference between low-intensity fires in grasslands and high-intensity fires in forests where there’s a lot of combustible or volatile material in what’s known as the fuel layer. The fuel layer is on the ground, where there’s dry grass, as in the savannas of Africa, but also leaves and fallen, frayed bark or branches. Occasionally, forests need a fire to burn away that dead material. It’s only when the flames climb up from the fuel layer and ignite hanging leaves that the trees come closer to danger.

Eucalypts, such as those native to Australia, burn fast because their leaves are very oily. In the western United States, it tends to be pine trees that burn. Both have evolved in their respective fire environments and can survive. “If you have a mild fire, some eucalypts will just put the leaves back on. If you have a more intense fire, they can start to put out leaves from the trunk. And if the fire is really severe, the entire top of the tree dies but it’s still alive underground, so they just send up a new trunk,” says Price. Other eucalypts are killed by fire, but they tend to have prolific seeding events right after the fire.

But humans keep reshaping their environments, turning them into fully urban areas or making the bush (at least partly) residential. Perhaps the best advice is that we develop a better relationship with the land and accept that wildfires are a reality. “We seem to have this attitude that we are superior to nature, that we can dominate nature, and it plays out in this sphere,” says Price. “No one would pretend you could prevent the next earthquake. But people and authorities seem to think that they can prevent the next bushfire from occurring.”

— This article has been provided by Deutsche Welle

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