About 1998, I read a lovely novel in which a man helped a planet in ecological trouble by using technology on his ship to carry out genetic engineering of local plants and/or animals. He told them the fix was too short-term and duly returned a 100 or so years later and fixed the resulting problem he had correctly predicted. And again once more later.
I think the helper might have found the ship abandoned and wasn't sure how to use the technology at first. I remember him being described as very lazy - carrying out all his work without leaving the ship.
I think he was human but I'm not sure; I think the planet was alien but I'm not sure - but it wasn't earth.
Any ideas?? Many thanks.
The Last Question:
And the mind said 'Let there be light'