Is there enough fresh water on the planet to turn all deserts green?

Question

If you spend enough time on the “educational” side of Youtube, you will come across short documentaries that talk about projects aimed at stopping desertification and climate change. One example is the green wall of trees, that multiple sub-saharan countries want to plant in order to stop the sahara from spreading. Another example are the plans to turn parts of the australian outback in to humid land by planting trees and building dams. My question is: Is there even enough fresh water to sustain all of those projects? Could you theoretically turn all deserts into humid forests?

In: 9

Answer 1

It’s not just about water really. Take the classic explanation of the water cycle. Ocean water evaporates. That evaporated water sits in the atmosphere where it’s transported by wind. This wind is in turn caused by the dynamics between warm and cold air as well as warm and cold oceanic currents.

Atmospheric water moves on air currents until it coalesces into clouds and eventually falls down to Earth in the form of rain, snow, hail and so on or freezes into glacial ice. All that water eventually flows into rivers, either on the surface or as groundwater and the rivers transport it back to the ocean for the next cycle.

The Sahara is so dry exactly because the local climate conditions cause moisture to evaporate from the Sahara and get transported out to sea. There currently is no moisture cycle that brings water into the Sahara, only a cycle that takes it out. Most deserts have environmental causes like that which cause the arid nature of the region.

So if you just start dropping buckets of water into the Sahara, you won’t be achieving much. You drop in a bucket of water and the climate conditions will suck it right out and drop that water back into the ocean.

And with all the greenhouse gasses we’re pumping into the atmosphere, the climate catastrophe is only speeding up and intensifying that process.

So the question do we have enough fresh water on the planet isn’t quite the right question. Trying to fix the Sahara by throwing water on it is a bit like trying to fill a bucket without a bottom.