16. L’arbre source

In a context where we are seeing a sharp decrease in water resources, trees and forests, generous sources of life, play a key role in the global water cycle and contribute to building up freshwater reserves underground. It is sometimes difficult for us to consider the tree as a living being, even though, just like us, it is made up of cells that reproduce and evolve to form a complex organism. They live on this earth, breathe, grow, feed and die.

Just like light and air, water is essential in the life of a tree. Water and minerals, captured in the soil by root hairs, flow through the fine rootlets, the roots, then up the tree’s trunk before arriving in the scaffold branches, secondary branches, smaller branches and leafstalks, eventually reaching the leaf blade and the veins to then escape into the atmosphere as water vapour. The tree makes its sap in the cells of the leaf, which contains chlorophyll, by combining water from the ground and carbon dioxide from the air, thanks to photosynthesis. The sap produced then travels down through the trunk to feed the tree’s living tissue.

Thanks to their foliage, trees can also intercept rainfall and slow down the droplets before they hit the ground. Plant litter, found at the foot of trees, then their roots, help to drain and store the water in the ground, creating flows that will go on to supply groundwater and streams.

L' arbre source (Source Tree) illustrates this principle by collecting water from the sky with a tree’s leaves.