How forests make rain
Traditional scientists believe that forests grow where there is ample precipitation, but they do not cause precipitation. Moisture gets carried inland when water vapour gets carried with winds. But precipitation doesn't decrease when we go deeper inland.
Forests have a lot more surface area for water to evaporate off of. Multiple canopy layers, shrubs, ground are all full of water that enters the air. So there is more water vapour in forests than in the oceans, even when there is less total water.
This moisture that rises and condenses into clouds drops the air pressure and creates an upward current bringing more water vapour to the forest. This sucks in water vapour from higher pressure areas like the ocean to bring rainfall inland. Forests bring rain through this process called the biotic pump.
How mushrooms make rain
The finding that these organisms can affect the weather has raised questions about how they could be employed to help us control the weather and what impact they might have on the climate more broadly.
Fungi make 50 million tons of airborne spores—enough to coat every square millimeter of Earth’s surface with 1,000 spores each. Since we now know that ejected mushroom spores can accumulate water in humid environments, it’s possible that they play an important role in rain-making over forests. Fungal spores likely serve as excellent GCCNs (giant cloud condensation nuclei), which are important rain seeds in clouds.
There may be a vast and previously unrecognized positive feedback loop acting over forests. Mushrooms, which spring up like tulips after a good soaking, make spores that act as rain seeds, which makes the rain that makes more mushrooms.
This would mean that climate change reducing rainfall over forests, will cause a drop in mushroom spore formation which would make droughts more frequent and harsher. The flip side of the fungal-rain feedback loop rears its ugly head.
If we want to thrive on this planet we need to preserve and regenerate the forest.
Learn more about the biotic pump:
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