Large yeast blobs spread across the land and devour them. Land masses become gigantic pita breads, and the oceans turn into frothing waves of India Pale Ale.
As I said, free, clean energy won't happen in my lifetime, but I believe it will happen. You need to think about it a long time to fully appreciate the impact. Look at everything we do today, and consider the impact the change would make. MH, don't talk about efficiency. It will be meaningless. It would take more humans than the planet could feed to impact the oceans significantly. All you're doing is removing the water, which later goes back. Not that much of the uninhabited land is farmland or ranchland. I'd say less than 40%. And with free energy, new methods would reduce the needed farm acreage probably 10-fold. Besides, you can grow as much food as you want on huge space platforms--the current limiting factor, the cost of the energy to transport things up and down, will no longer matter. Effects on psyche: I suppose the murder rate will be the built-in correction. But you and your friends could always take your private shuttle and abandon the planet altogether. It would be a new world; whether or not a brave one would have to be seen.
Scronch