I would assume that the unchecked human-generated expansion of the desert reduces the diversity of what was previously not desert.

A desert is a collapsed biome relative to when it was not a desert. As such, it has a huge debt to repay to what was lost due to the desertification. If the desertification is not reversed, it will go only deeper into debt, killing what little life is left there via a continued rise in temperature. As such, what is being done to reverse the desertification and restore the biome is most appropriate.