Railroads have lasting impacts on natural landscapes. This trail used to be a railroad. Railroad beds, like road beds, are designed to drain water away from the tracks, so there is usually an embankment of crushed stone called "ballast" that allows for fast drainage. However, the large, dense mass of the ballast can prevent the free flow of water across the landscape, so there is often more water on one side of the roadbed than the other. Along this trail, the amount of water is a driving force determining the plants and trees that grow, with mature aspens on one side requiring drier conditions and gray birch on the other side able to colonize wetter conditions.