There's cacti because on the forums page there are challenges one involving cacti

There's many survival maps, but why do we always start with some CACTUS? It's bugging me. Cactus is useless. You can use it to dye some sheep after you've smelted it, but it's hard to find fuel, sheep and furnaces in the end. It makes no sense! And now that the mobs are smarter than ever before, why would they walk into a cactus?

Seems cool! I might give it a go (:

Oh yeah, I'm the first one to download this world! :D