We know, for example, that dust from the Sahara circulates the globe and brings nutrients to US soils.

Eh, the Amazon rainforest survived the African Humid Period, so it's probably fine.

More to the point, even if this thing is big compared to the average solar farm, it's still small compared to the scale of geoengineering. For example, enough solar panels to power the entire US would only cover a small fraction of the Chihuahuan Desert:

(source)