I developed a theory (actually less than a theory, more than a random thought) that the reason most animals are so much smaller physically now than in the past has to do with the quantity of biomass (ie. carbon) available and distributed around the planet. It is less now than it was. How do we know this? Coal, peat, oil all lock huge quantities away from use by life.
By digging all that stuff up and putting it back in the biosphere (by burning it) we are simply recycling the carbon to where it belongs.
If we invented a “clean” inexhaustible power source tomorrow, the environmentally responsible thing to do would be to dig up all that coal, etc. and burn it anyway. Leave it to the enviros to ALWAYS take the side of sterility and death.
I’m firing up my lawnmower right now. I’ll let it run all day.