Edit: This might actually be a Terrestria issue; the Lush Desert is incorrectly set to the "Ocean" category so it's quite possible the Taiga Island was trying to generate in an actual ocean... which just happened to be made entirely of sand. Closing the issue, will re-open if I find more examples once Terrestria is fixed, and after checking to ensure the correct category in the source code if I can find it.

The mod Lakeside, which removes Vanilla lakes and places new, nicer lakes in their place, seems like it may be having some issues with Overworld Two. Lakeside is generally only supposed to generate "island" biomes in the center of its new lakes, but for some reason I had a "Taiga Island" biome from Lakeside spawn directly next to a Lush Desert from Terrestria.

I'm putting the issue here since this is the only overworld-related terrain gen mod I have right now, and this seems more like a terrain issue than a biome issue (since Lakeside should work fine with any biome mods out of the gate?)

The offending area as seen on Xaero's World Map: