ok I finally found one, half inside one of those huge horizontal swamp trees (the indestructible kind). Couldn't even see the torches until I was facing it from just the right angle, which only happened because I was running for my life from one of those new "stump spiders" or whatever they are.
"7 areas" would be look at your map, determine the average amount of space a continuously connected swamp takes up, and multiply that by 7. that's about how much swamp I searched just to find 1.
However, if they are all hidden half inside other objects now, I've probably overlooked a few as I haven't been scrutinizing things that seemed to be giant swamp trees.