It's a bit hard to see but I guess there are millions of ants living in your compost.
I expect you had better poison them, you can get stuff from Homebase and B&Q, places like that.
That might also mean chucking out the top layer of your compost heap because I think poison could ruin it.
You use apostrophes a lot don't you
Ant's invasion does imply someone called Ant invading. Sometimes better to miss out on an apostrophe than to stick one in where it's not meant to go.