Vapor barrier for woodshed?

I built a 12' x 8' woodshed and split and stacked wood to fill it. Afterward, I read that a vapor barrier on the ground is important. The wood is sitting on pallets. Any thoughts?

I built a 12' x 8' woodshed and split and stacked wood to fill it. Afterward, I read that a vapor barrier on the ground is important. The wood is sitting on pallets. Any thoughts?