Building in an area stops creatures from spawning. It can be as simple as a few power poles and lines. Venture as close as you can manage, and reach as far as is possible with the build tool. Leave the area, and come back, and spawns will be gone from that immediate area. Rinse and repeat.
I know, it sorta sounds like a pain in the butt. Probably not nearly as much of a pain as it would be to recode that entire aspect because YOU can't deal with it.