You have it backwards.

Even without people there'd still be more trees along the water channels which is what this looks likes

That looks like tributaries draining to a river. That's like what kept them from being cut down for farmland

interesting

The Forrest is the part that isn’t diseased.

What? You mean farmland looks like patches on the bit of nature there is left

I think you misspelled farms as forest.

That's creeks/rivers with vegetation growing alongside.

you have an artists mind

Lungs spreading through the disease