Long live the fire!
How Plants Resist Fires
Audio 02:41
Fires ravage California on September 9, 2020. AP / Noah Berger
By: Florent Guignard
9 min
Flames, the source of life for certain plants that grow in the Mediterranean climate.
What to put into perspective the latest tragic information from California, where the record was broken this week: more than 10,000 square kilometers have soared.
An ecological disaster?
Not necessarily.
Publicity
Fire has its virtues that emotion ignores.
The spectacle of the fires this year in California has been going on for weeks, with its share of desolation, charred landscapes and human casualties.
And yet ... In the Mediterranean climate, and this is the case in much of California, plants have learned to live with flames.
This is evidenced by what we could observe after the last major fires in Australia.
“
Six months after the fire went through, it's superb, it's all green.
And we haven't lost a plant.
The tree is gone, but the sprouting is right next to it.
So the plant is still there.
And it's the same in California,
”explains Alain Menseau, botanist at Domaine du Rayol, near Saint-Tropez, on the Côte d'Azur, a global garden that brings together the vegetation that grows in the Mediterranean climate, in Mediterranean of course, but also in the Cape region in South Africa, in a small part of Chile or even in the south of Australia.
An adaptation to fire that required millions of years of evolution.
A secondary development for the vegetation of the south of France, initiated by overgrazing, when wild animals, such as deer, came down to the coast for one or two months “to
eat all the vegetation.
But eat everything
, says Alain Menseau.
This resistance to overgrazing is the same resistance as that triggered in the face of fire, since the plant knows how to start again when all the aerial part has been removed.
"
There are no plants without fire
Different strategies are implemented for Mediterranean plants.
First, there are trees with natural protection, such as the cork oak.
Others who have developed an underground trunk: the strawberry tree, capable of regrowing even when the aerial part has completely burned.
"
From this underground trunk will start again branches, which we call trunks, because that is what we see
, details the person in charge of Domaine du Rayol.
But they are in fact branches.
And then there are the plants that need fire to reproduce.
The Aleppo pine, very present in the Mediterranean, waits for the passage of fire to germinate, “
because it cannot withstand competition on the ground.
"
The seeds of the callistemon, here at Domaine du Rayol, contained in wooden shells, will only be released with the passage of fire.
RFI / Florent Guignard
Two days after the flames, the pine nuts containing the seeds explode and cause "a rain of seeds".
Since fires often take place at the end of summer, the first rains, the real rains, come with the fall, and the seeds that have fallen on a soil enriched with ash begin to germinate.
The autumn rains that run off after a fire, loaded with carbon, are thus an excellent fertilizer.
The Australian calistemon simply cannot germinate without the passage of fire.
The shrub keeps its seeds throughout life, locked up, protected, in wooden shells.
And it is the flames that will release the seeds by exploding the shell.
“
Of course there is loss, depending on the intensity of the fire.
Out of thousands and thousands of seeds, it's never 100
% successful.
But the main thing is to have 2
% success
.
The proteas of South Africa, a flower found on the jersey of South African rugby players, alongside the springbok, they need the smoke of the fire to reproduce.
“
For nurserymen, we thus produce blotters, soaked in smoke.
We water, and the seeds germinate on their own.
On a smokeless blotter, it will never germinate.
"
No home in the burning forests
In the Mediterranean climate, there is no life without fire.
And that is why humans sometimes cause controlled, deliberate and controlled fires.
This is the case for example in the parks of South Africa, after fifteen years without fire.
Without regular fire, "
the vegetation will become too dense
, reminds Alain Menseau,
and when the flames arrive, because they always end up
happening,
the fire will be too hot, seeds will be too destroyed, and we risk losing biodiversity.
"
Before being an ecological disaster, the fires under therefore often, first, a human disaster.
“
The problem
, concludes Alain Menseau,
is to build houses all over the place, in the middle of the forest.
It's beautiful, it's magnificent, but it becomes catastrophic with the passage of the fire.
We don't have to build our homes in a burning forest.
This is not the right place
!
"
"
Are the birds all flying in the sky
?"
"
Most birds are able to fly, the hen a few seconds, and up to 10 kilometers of altitude for the Rüssel vulture, which flies especially over the Sahel.
But some forty families of birds have been grounded for millennia.
Like an airplane without wings, but with other qualities.
The penguin can swim.
And the ostrich, too heavy to fly, is capable of sprinting at 80 km / h.
The dodo, on Mauritius, had lost the usefulness and therefore the use of its wings, atrophied, because it had no predator.
Until the arrival of the colonists, who drove him away, and introduced pigs in particular.
A century after its discovery, the dodo had disappeared.
Newsletter
Receive all the international news directly in your mailbox
I subscribe
Follow all the international news by downloading the RFI application
google-play-badge_FR
Flora
Environment