Air bricks around the bottom of your home are there for a reason!
Their purpose is to ventilate the under floor space. You normally see them if you have timber ground floors. If they become blocked for long periods then the floor timbers can start to rot as dampness builds up in the unventilated space. .
Many modern houses have suspended concrete beam floors. Here the purpose is to stop the build up of potentially damaging dampness and condensation in the sub floor void.
So, if you are digging over the flower border, clearing Autumn leaves or laying a new path double check that your air bricks are free of any obstructions.