What would most likely increase the number of squirrels living in an area?

If the area had an uptick in rain the trees, shrubs, and other plant life would really take off. This in turn would cause them to produce more food for the herbivores. The squirrel population would reap the benefits of this, especially if there were few or no predators in the area. This a bad thing, as they are destructive (but cute), they will damage property and surrounding plant life, just by going about their squirrely business (breeding, foraging, nesting, etc).