What would be the natural reason for the surface of a planet to be toxic or otherwise uninhabitable to animals but not plants? This planet is not Earth and life would have evolved this way from the beginning.
Ideally the animals would have to live higher up (trees, rocks, maybe even floating islands) and would all have evolved to fly or find another way to navigate treetops/the air.
Plants would still thrive on the ground and animals would still be able to go down to the ground but not for long.
(when I say animals I mean animals and sentient species)
What I've thought of so far:
- a layer of CO2 coats the surface (or higher % of CO2) which means plants can grow but animals can only go down for a quick time (or have developed ways of holding their breath for a bit longer).
- the ground burns for some reason, but plants have evolved to resist it
- the ground is toxic to touch, whatever the toxicity is it's something plants use
I'm looking for complete and plausible ideas or reasons animals can't live on the ground but plants can.