00:00We have three large groups of mushrooms in the forest,
00:02and now I'm going to take you to the mushroom forest,
00:05behind, in this wood, to convince you that these mushrooms are essential for the good functioning of the forest.
00:3199% of the mushrooms are microscopic filaments that colonize the soil or the dead branches.
00:37And at certain times of the year, when the conditions are full,
00:40in the fall in particular, when there is a lot of humidity,
00:43they form this sexual apparatus, where the formation of spores takes place.
01:00In fact, it is not a root that we have there, it is a mushroom root.
01:04And it is these little roots there, these millions of little roots,
01:07these hundreds of millions of little roots, that will absorb these nutrients.
01:11The tree pumps phenomenal quantities, tons of water every day,
01:15but it also needs considerable quantities of nutrients.
01:23This network of mushrooms, which we have here,
01:27this mycelium network can cover square kilometers.
01:30So if we try to calculate roughly,
01:33half of the mass of the forest is mushroom,
01:37but not the mushroom that we pick up in the fall.
01:39This network is an underground net that colonizes the entire litter,
01:43which is around us, and which connects the trees to each other.
01:57This dead tree is already badly degraded by the decomposing mushrooms.
02:02You will see, if I remove this part there, which is already terribly degraded,
02:07we see, we guess, a part, a whitish area there.
02:10In fact, it is the mushroom filament network that is consuming the tree.
02:16So this network, which looks a lot like cables,
02:21is mushroom, which is made up of microscopic filaments,
02:25but which are capable, which have the ability to assemble
02:29to form much more rigid structures.
02:32And thanks to these structures, it can go very far,
02:35explore all the parts of the tree and digest.
02:38It is thanks to these decomposing mushrooms
02:41that the cycle of nutrients in the forest will be ensured, looped.
02:45It recycles carbon, but it also recycles all the other nutrients
02:49of dead trees and plant debris.
02:52And that's what's going to make the soil rich and fertile.
03:04We probably have a tree that was attacked
03:07by the third group of mushrooms that live in the forest,
03:11parasitic, pathogenic mushrooms, which attack living plants,
03:15which will colonize them and eat them on foot, devour them.
03:19I call them the truants.
03:21And we, the foresters, we don't like them very much
03:24because they cause significant damage in the forests.
03:34Mushrooms could help us in at least three ways
03:37to fight climate change.
03:39The first is to select symbiotic mushroom species
03:42that help trees fight drought.
03:45The second way is to do everything to promote the development
03:49and growth of this mushroom network in the soil
03:52because 50% of the carbon is stored in this mushroom network
03:56in the forest soil.
03:58And the third way is to promote the interaction
04:01between symbiotic mushrooms and trees
04:04because it is these symbiotic mushrooms that stimulate
04:07the growth of trees.
04:09And by stimulating the growth of trees,
04:12they make wood and wood stores carbon.
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