Dangers of "Natural" Energy Sources

now, i've had a few discussions with people that are anti-nuclear. we're talking fission. ok, its dirty, etc. etc. i bring up the idea of fusion and they still hate it. fair enough. they advocate "natural" energy sources such as solar, tidal, etc.

now, my point is this: considering the idea that a butterfly flapping its wings in britain can cause a tornado in australia (due to chaos), what effect might tidal / solar / wind power have on the biosphere?

my worry is that we have absolutely no idea at all - to the best of my knowledge - what effect "natural" energy sources might have on the biosphere. just general thoughts have led me to thinking of massive-scale monte-carlo simulations required for even vague guesses at the effects.

so, anyone got any comments on this? anyone know of any research in this area?

- qo.