22nd March is World Water Day. A day dedicated to a resource essential for life on this planet. A resource about whose future gloomy predictions can be read. To prevent these from coming true, we want to devote our maximum attention to the issue today. The worldwaterday.org website says: "Water means different things to different people. This conversation is about what water means to you."
What does water mean to those of us who plant trees?
The obvious answer is that trees, even the most tolerant ones, owe their existence to water. But the relationship between trees and water is actually more complex. It is based on a mutual exchange - trees owe their existence to water, but they also help to conserve this precious element. What positive effects do trees have on the water resources of our planet?
Trees that refresh
Colleagues who regularly visit Africa sometimes tell us that locals often talk about "trees attracting water from the sky". This sounds more like superstition than science. But it is true...
The tree absorbs water and minerals through its roots. These are transported through the trunk to the crown of the tree. There, in the leaves, transpiration takes place in addition to chlorophyll photosynthesis. The movement of water within a plant and evaporation from the above-ground parts, such as leaves or flowers - that is the scientific definition.
Treetops do not only provide shade. They also naturally cool their surroundings. Their role in relieving the environment can be crucial, especially in heat islands in large cities. In redefining urban environments, planning for the presence of trees can become a strategic decision for the future.
Trees that filter
Clear, drinkable water is one of our planet's most precious commodities. However, its production and conservation continue to present us with major problems. When looking for solutions, the forest may not immediately come to mind. But it should: because trees can filter water.
Let's take a typical temperate forest as an example. Here, about half of the water seeps into the groundwater and is filtered and purified, mainly by tree roots, but also by rocks. In interaction with the transpiration described above, very clear water is produced here. So clear that researchers believe it is the purest water on the planet.
So some trees can also purify water in other ways: Like the Moringa. We have already tested the impressive abilities of its seeds ourselves.
Trees that insulate
Unfortunately, we are increasingly experiencing how extreme weather events can have catastrophic effects on the environment. With serious risks - also for humans. Flooding of rivers, strong storms at sea or landslides.
Trees can help prevent and contain the effects of all these potential dangers. With their roots, they are able to hold the soil so that it is not washed away and the risk of landslides is reduced. At the same time, their presence on riverbanks and in coastal areas can curb the effects of erosion. Which significantly reduces the risk of flooding. Consider, for example, the vital role of mangroves in many of the planet's ecosystems.
One thing is certain: without this interaction between trees and water, our global ecosystem would not function. That is why it is so important to preserve this natural relationship between water and trees. We want to contribute to this with our work in the global south.