> Every single time it's had absolutely horrendous consequences often with millions of human deaths attached

Although I think it's best for nature to leave things how they are, draining the Landes in France (a swampy area comparable to that of the Everglades) and replacing it with a pine forest only had positive impacts on the humans living there (if only because it was a major step towards eradicating malaria in France).

To be honest though, it was originally a forest, and had turned into a swamp after being deforested by humans in the early middle ages.