Typical for a desert is the heat during the day and the cold during the night. The air is very dry and rain is a rare guest. They are the most extreme environment on our planet.
The surface of desert type landscape needs to be in balance to keep the climate stable. We cannot afford to lose deserts, but we also don’t want them to expand.
The radiation in the desert is immense: A lot is being received, but also a lot is being reflected back. If the desert expands, there is a direct impact on the global average temperature, further the water evaporation increases at close areas.