So, if safety is the main factor here because it will be a similar swamp with leaves on top soon enough, what about leaving it be and securing the backyard instead ?
Install keyed deadbolts on the back door and use wood strips secured to the outside window frames so they can't open. Also lock the fence so there's no easy access from the front.
Install keyed deadbolts on the back door and use wood strips secured to the outside window frames so they can't open. Also lock the fence so there's no easy access from the front.