Question

How does capillary action help sustain life on earth?

Answer 1

This helps us sustain life by  the tendency of a liquid in a capillary tube or absorbent material to rise or fall as a result of surface tension.

Answer 2

VzDeath is correct.  It also helps the water and carbon cycle.  In the water cycle there is something called Transpiration where water is taken in the roots of plants and travels up the stem through capillary action and into the leaves.  THe leaves release the water as a by-product of photosynthesis and to cool its leaves.  With out this capillary action the water cycle wouldn't be so complete.