[lasfter]

[1] argues a crucial component of greening is trees "pumping" water from the oceans inland and creating nutritious soil. Otherwise evaporated water is simply blown away by the wind. I'm sure other local terrain (e.g., mountains) play a part in locally retaining evaporated water and creating conditions for rain.

[1] The Hidden Life of Trees: What They Feel, How They Communicate—Discoveries from A Secret World by Peter Wohlleben.