A new study published in found that cleared ski slopes are more environmentally friendly than graded ones, according to the . Cleared slopes are created by cutting down trees to open up an area. Worker leave smaller vegetation and topsoil alone. Graded runs use bulldozers to smooth the ground, which removes vegetation and topsoil. By only removing trees and other tall vegetation, cleared runs leave seed beds found in topsoil intact, which supports future plant growth and wildlife in general. Some ski resorts machine-grade their runs because a smoother surface means less snow is needed to open the hill. However, research from the study showed that graded hills only opened a week earlier than cleared ones, on average. The study, which is the first of its kind to be done in the U.S., observed ski resorts in and around the Lake Tahoe Basin.
— Lisa Lombardi