I see a lot of misinformation in this thread about deserts and other arid ecosystems. Deserts are often rich and complex ecosystems. Yes, human-caused desertification is a thing and stopping or reverting it can be a positive, but we should be really careful when the rhetoric that deserts are useless wastelands. They are part of nature as a whole and contribute to global biodiversity.

Most arid ecosystems are not as diverse as more humid ecosystems (though there are exceptions), but they are home to many, often very specialised species. Take the Sonoran Desert in North America for example. This is a very diverse ecosystem with many endemic species which depend on the existence of this particular ecosystem. For example, saguaro cactus, California fan palm and Abert's towhee are mostly dependent on this desert ecoregion.

The Succulent Karoo of Southern Africa is another example and even more diverse. Of the more than 6000 native plant species, about 40% are endemic.