Life is full of opportunities to learn. "Gotta learn something new everyday." Here's a bit more: There are about 6000 solitary bees that live on the NA continent. Most of them make small tunnels in the ground, and some carve holes in wood, e.g. trees, posts, etc. The ground dwelling ones on average go about 6 inches deep. So that woven plastic "landscape cloth" interferes with them. If they are beneath it when installed, they can't get out. If they are above it they can't make proper homes for their babies. Happy Spring!!