that is exactly my point. It isn't unpopulated or abandoned. A "desert" able to support cactus has to be VERY populated, and in the case of the desert that holds saguaro, more populated than most temperate forests (going on a number of different species per area rather than pure density of seperate entities, 'cause you can't compete with grass). "desertification" turns areas into sandy-unpopulated areas, and happens no matter what temerature it is.
Oh come on! For one, that is the ancient roots of the word, not the modern definition. The modern definition is any place less than 250 mm of precipitation per year, end of story. Some places are misnamed deserts because they look like deserts but actually get too much rain to qualify - but even among actual deserts there is a huge variety. There are sandy deserts, dusty deserts, rocky deserts, icy deserts... There are totally barren deserts, there are deserts with so much vegetation that from far away you can hardly see the desert 'floor' for the plants. Hell, you can even cultivate crops in many deserts (the Judean Desert being a good example).
Also, desertification will only result in sand if there is already sand present. It will only result in dust if there is dirt. If the landscape is mostly rocky, there won't be copious amounts of dust and sand, no matter how bad the desertification. The temperature isn't really relevant, but the local geography is supremely relevant.
If you compare to African prairies, most american "deserts" are freaking gardens. And I'm not even talking about the Sonoran desert, much of the great basin (thats Nevada) and... chibihaun? something like that (Texas and new mexico) are only "deserts" by record of rainfall. The latin word "abandoned place" does not describe places where cacti grow, so they are misnamed.
The latin word is not relevant. That is the etymological root. The only definition of the modern word "desert" is the one regarding rainfall. Deciding "oh this isn't a desert, it has so much more vegetation than that desert over there!" is ridiculous. If a region is 'only' desert by record of rainfall, then it is a desert because that is the only requirement. What you are used to thinking of as classic, sand-swept desert makes up a miniscule fraction of the deserts on the planet. If one desert happens to have lots more vegetation than another, or even more vegetation than some non-desert, then there are other factors at play besides the rainfall. Maybe it gets close to the maximum 250 mm per year, maybe it has excellent nutrients and just the right amount of sun. Maybe certain species managed to adapt excellently to that specific environment.
Point of case: "This does not work" refers to the association of cacti to "abandoned place" deserts. Most hot and dry North America "deserts" are misnamed, and Stardock should not make the mistake of including cacti in unfertile deserts.
Yes - many if not most so-called deserts in North American are misnamed, but that does not change the fact that real deserts can support significant plant-life.
Here is a list of the major deserts in North America for anyone who cares.
If Stardock is going to have places where cacti grow, they should be hot-fertile lands (and if flat, they should be called prairies or savanas, even though that is now what fits common American usage of the term).
First, elevation and the like is totally irrelevant. Desert can be mountainous, hilly, covered in dunes, and even perfectly flat. A savanna is tropical grasslands with an open tree canopy - totally different from desert. But more importantly, Stardock should not limit themselves to those kinds of rules - they are designing a fantasy game world. They should do whatever they need to do to make it look rich and interesting and good. If that means sticking cacti in every desert, so be it. Now, if they decide that doesn't give the right look to the game, that's another story all together.
Here are some images of the Northern Basin desert in North America:


Here are some pictures of the Gobi in Mongolia/China:



And here are some of the Judean desert:


And here's an image from the Colorado Plateau desert:

These are all deserts. You can yell and scream all you want - no matter how sandy, green, rocky, flat, hilly - they are all deserts and there is nothing you can do about it.