It is a wet year, so things are going to be more green than last, but the great green wall is a lot more than simply trees. It’s a ton of agricultural tricks to help retain the little rainfall they do get. So in a year where they get a ton, it will get a lot more green as the water is actually being retained. Iirc they dig a ton of multi levelled crescent shapes to retain the water and plant various levels of crops to use said water. Honestly a lot of it is just breaking up the dry ass ground over there and keeping water in it so plants can start growing. Once it does though, there’s better ground that on a good rainy season will grow plenty more greenery.

But yeah, it’s not JUST the wall. It’s also a very wet year, but the odd two combined make it a lot more green because usually in a rainy season that dry ass ground is so hard most things won’t grow anyways. But after years of cultivation, things can grow there.