A few bumps under the snowy slopes are better for environment

 Most people schussing down a ski slope probably don’t wonder if it’s been cleared or graded and why the answer makes a big difference to the surrounding environment. 

A new study out in December’s Ecological Applications finds that there is a big difference between a downhill ski slope that’s been cleared (cutting and removing shrubs and trees) versus one that has been graded (extracting tree stumps and boulders and leveling out slope irregularities).  The former leaves the top layers of soil and existing seeds banks intact while the latter removes much of the topsoil and most of the plant life. 

Graded (left) and cleared (right) ski runs. Photo: JW Burt.
Graded (left) and cleared (right) ski runs. Photo: JW Burt.

 University of California researchers Jennifer Burt and co-author Kevin Rice studied seven winter resorts in the Sierra Nevada range and found that cleared ski runs were functionally similar to nearby forests, sharing much of the same plant composition, diversity patterns and soil characteristics.  Their graded counterparts, however, had negative impacts on water storage, nutrient cycling, soil, and biodiversity.

Burt noted in a statement that:

This begs the question as to why any downhill runs are graded.  Resort managers told us that ski-run grading reduces surface depressions, hummocks and boulders, which means that less snow-about 20 inches on average-is required to open a graded run that a comparable cleared run.

Resorts with graded slopes can therefore open their runs about one week earlier than those with cleared runs.  But, according to Burt and Rice, the extra week’s revenue may be partly offset by higher maintenance costs associated with erosion control and other measures the barren slopes require come summertime. 

The study is available here (subscription required) and the abstract may be viewed here.


Burt, J., & Rice, K. (2009). Not all ski slopes are created equal: Disturbance intensity affects ecosystem properties Ecological Applications, 19 (8), 2242-2253 DOI: 10.1890/08-0719.1

Author: Nadine Lymn

ESA Director of Public Affairs

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