“Five months without water is enormous!
Under the foliage of a large oak tree, the observation is made with a touch of fatalism.
Gauthier Malherbe is a technician at the Poudrerie park in Sevran.
An urban forest of 142 hectares managed by the department of Seine-Saint-Denis and disciplined by a grid of alleys, a memory of a not so distant military occupation, linked to the manufacture of powder and explosives until 1973.
The unprecedented duration of the summer drought in Ile-de-France ended on September 23.
Since then, successive waves of violent showers have been washing the soil in the Paris region without stopping, but they arrive too late for the vegetation.
Socketed like small precious stones in the concrete meanders of the suburbs, the urban forests of Seine-Saint-Denis - which will remain well open during confinement - are under pressure: overcrowding, urbanization and climate change.
How do they resist heat waves and lack of water in spring and summer?
“We don't really know where we're going today, because we don't have enough perspective,” admits Gauthier Malherbe.
Leaves that dwarf and turn yellow
Parc de la Poudrerie, regional forest of Bondy, Bois de Bernouille in Coubron, La Couronne in Clichy or Les Ormes in Montfermeil… These groves and coppices which occupy 400 hectares are the shreds of the old forest arc of Bondy.
The legendary haunt of brigands and thugs in the Middle Ages stretched from the Bois de Vincennes, in Paris to Fontainebleau, in Seine-et-Marne, before being over-exploited in the 19th century and then gradually devoured in the 20th century by residential areas .
"Here, we are working on what our elders have bequeathed to us", summarizes Gauthier Malherbe.
At the Poudrerie, where we find oaks, hornbeam, beech and ash, the oldest trees are 200 years old.
"More than 60% of our afforestation is made up of oaks, some of which are nearly 300 years old," explains Pierre Martin, technician responsible for the Bondy regional forest.
Parc de la Poudrerie, Vaujours, end of September.
LP / Claire Guédon
“Old trees, especially beeches, have a great need for water and if they lack it, their heads are not always supplied with water,” explains Pierre Martin.
The leaves are seen to dwarf and turn yellow.
The lack of water accelerates dieback in old subjects.
"
Malika, a resident of Clichy-sous-Bois who did not go on vacation this summer, admits to having been surprised to “see in early August, the dead leaves start to fall” on certain paths in the Poudrerie park.
"There are also trees which have completely burnt branches and that is also new", she judges.
Seine-Saint-Denis newsletter
Every morning, the news of your department seen by Le Parisien
I'm registering
Your email address is collected by Le Parisien to enable you to receive our news and commercial offers.
Learn more
In itself, a heat wave or a drought is not insurmountable, according to experts.
“Forests have a certain resilience, continues Pierre Martin.
But it is the repetition of these climatic phenomena that is problematic because the trees are weakening.
"
Insect and fungus attacks
Embrittlement can promote attacks by insects, fungi and bacteria that have become plagues in Ile-de-France in recent years: chalarosis in ash trees, chestnut canker, elm gall, spotted phellin in plane trees, chestnut ink … Several of these diseases are exploding, without really explanation.
Parc de la Poudrerie, Vaujours, end of September.
More and more chestnut trees are victims of canker, a disease that causes them to lose their leaves.
LP / CG
What new species to plant and how to anticipate the climate to come?
“It's far from simple as a question, continues Gauthier Malherbe.
If we test a tree accustomed to high heat or drought, we must also consider its resistance to frost and cold.
"
The National Forestry Office (ONF) has also launched a network of experimental gardens across France devoted to the main species threatened by climate change: oak, spruce, fir and beech.
The aim is to "find the trees of the future and facilitate genetic adaptation" by comparing local plants with those imported from other regions.
While waiting for the first results, in Seine-Saint-Denis, we choose to “accompany nature”, as Gauthier Malherbe summarizes.
"And we favor regeneration," confirms Pierre Martin.
Almost a million visitors each year to the Bondy forest
Local residents value wooded areas like the apple of their eye and often go there.
Owned by the green spaces agency, fenced and with opening hours, the Bondy forest seems to be under wraps, but yet it receives between… 800,000 and one million visitors on its 185 hectares!
A record which makes it one of the most visited forests in Ile-de-France, if we had to reduce the number of walkers per hectare.
“It's very calming to come and run in the Poudrerie park,” says Malika.
People who equate Clichy, Montfermeil or Sevran with cities and traffic would be very surprised if they came.
It is our breath of fresh air and I will not stand to see these small forests near my home disappear because of global warming.
"
"Trees are the only ones to connect people to nature in dense areas"
A point of view shared by Gauthier Malherbe: “Trees are the only ones that connect people to nature in dense areas.
They are urban clocks that recall the seasons and that the inhabitants watch them grow up.
The trees have a very important symbolism.
"
The town of Coubron, which is home to the 45 hectares of the Bois de Bernouille on its territory, is well aware of the challenges.
“The inhabitants of the surrounding communities come to us to seek greenery, underlines Ludovic Toro, the mayor of Coubron.
But to maintain the wood, we must give ourselves the means and the endowments.
"
What will it be in fifteen years?
“Nature is coming back very quickly,” hopes Pierre Martin, who remembers the 1999 storm, which destroyed a third of the Bondy forest.
It was a disaster but spaces opened up, dormant seeds sprouted, allowing variety in the plants.
Diversity is also an essential key to overcome climate change and disease.
"
VIDEO. In the Vosges, the forest threatened by global warming
