How do forest fires naturally die out

The forests of the world are on fire - the large overview of the sources of the fire

The forests of the world are on fire - the large overview of the sources of the fire

Forest fires are becoming more extreme. Nature recovers from it. But the released C02 further stimulates climate change.

Australia is on fire. 25 people have lost their lives, 2,000 houses have burned down, and entire areas of land where Australian animals lived are destroyed. It is estimated that 100,000 farm animals and nearly a billion wild animals have died in the three states of New South Wales, Victoria and Queensland. Images of burned kangaroos and koalas go around the world.

But actually the animals in Australia are used to forest fires because they occur regularly.

"If the fire is not too strong, the reptiles disappear into a mouse hole, the koalas climb into the 25-meter-high treetop and survive a normal ground fire."

says Robert Zingg, curator and zoologist at Zurich Zoo. The Australian animals have lived with fire for thousands of years, but this time it hits them. This has to do with the large area and above all with the high wind speeds. The winds keep directing the fire in different directions, leading even animals as mobile as the kangaroos into deadly dead ends. In addition, many roads in Australia are fenced so that the animals cannot avoid them. “It's not just the fire that is deadly, but above all the smoke gas,” says Zingg.

The koalas that live in Australia like on "islands", separate forest areas, are less mobile. There is no way to go to the next forest. “The fires will wipe out local populations, so there will be entire areas without koalas,” says Zingg. However, the animals that specialize in eucalyptus will not become extinct. This also applies to the Echidna, the kangaroos and the many monitor lizards, the giant lizards.

Australia's ecosystems are adapted to forest fires

This is confirmed by Harald Bugmann, Professor of Forest Ecology at ETH Zurich. “The ecosystems of Australia outside the tropics are adapted to forest fires. Even if many animals are dying now, from nature's point of view this is not a catastrophe; the ecosystems will recover. "

But first the fires have to stop. Rain is only expected in February and the fire brigades are overwhelmed.

"As a rule, forest fires cannot be extinguished if they have exceeded a certain - relatively small - size"

says ETH professor Bugmann. If several hectares are burning, the only thing the fire brigade can do is to prevent it from spreading in certain directions. The vegetation that has not burned down is moistened, or vegetation-free firebreaks are created. "Even though that doesn't always help." Fires naturally only stop when the weather changes. When the wind changes direction and the fire must continue to burn against the wind direction. Then at least the speed of propagation is massively reduced. There is also a standstill when the burning material goes out - when the fire reaches a lake shore, the sea or an upper edge in a mountain range. "Because the fire usually burns upwards and only very slowly downwards, if at all in that direction," explains Bugmann.

The rain is of course helpful - in comparison to this, extinguishing water is the proverbial drop in the ocean. "So the prospects are not so good that the fires in Australia will stop soon, because the weather is still extremely hot and dry."

The big fires are seen as a beacon for climate change. It is difficult to clearly attribute individual events to climate change. In principle, they could also occur in a climate that is not influenced by humans, says Bugmann. But such unlikely extreme events have accumulated strongly in various places on the globe since 2000. "That corresponds to the pattern that we expect in a climate that has changed by humans," says Bugmann.

As long as such events as this year do not occur more frequently, the existence of the forest ecosystems is not threatened. A greater accumulation could, however, result in a change in vegetation from closed forest to savannah structures and even grassland. Climate change would therefore lead to a «vegetation shift». If the emissions were not reduced to zero within a few decades, such shifts in vegetation are very likely. “Not only in Australia, but also in many other places around the world. For example in Valais, where it is already very dry today. "

Extreme forest fires in Siberia and the Amazon

In the summer it burned for months in Siberia. It is normal for the taiga with its endless forests to burn at this time of year. But this year the fires raged worse than usual and also endangered the peat soils. They are great stores of carbon dioxide. In August 2019, the rainforests in the Amazon also blazed. There, the trees and soils also bind large amounts of carbon and, together with the oceans, take part of the man-made emissions of CO every year2 on. Destruction of the forests leads to additional carbon emissions and also destroys the CO2-Reduce.