Why do hurricanes produce low pressure ?

Question

What are the effects it has on the land below it?

Answer 1

Actually, the low pressure is what ultimately causes the hurricane.  There is little effect on land, but the low pressure is what causes the storm surge.  The low pressure at the center of a hurricane causes the surface of the ocean to rise up slightly.  The lower the pressure, the higher the storm surge.  

Answer 2

Only low pressure systems subsequently become hurricanes.