I think he's referring to nature making less florida.

OTOH there's a case to be made for keeping florida diluted.

erosion actually creates nests for various sea birds

Erosion makes gravel and sand, which are quite useful. It also makes minerals and nutrients accessible to life.

But we spend a lot of time and money managing erosion, and at the same time (often accidentally) create lots of erosion in other places. I doubt extracting tidal energy will have effects on a global scale, though it might cause some local changes