CONSERVATIONISTS have never liked ski resorts and for good reason. Trees are chopped down to make way for trails that skiers can use. This breaks up forest habitat and stresses local species that are disturbed not only by the construction but also by the skiers themselves during the day and the maintenance crews at night. The machines used to create a smooth piste compact the ground and remove the topsoil, leaving scars down mountainsides that are clearly visible when the snow melts, as are the pylons used by the ski lifts. Yet a new study has revealed that certain ski slopes have unexpected ecological benefits.
The most popular ski resorts in Europe are at high altitudes, where snow falls early in the season and, with luck, regularly throughout it. Most studies of the ecological impact of skiing have examined the ecological devastation caused by these resorts. However, few studies have examined the impact of skiing at resorts popular in the American west that are typically built at lower altitudes, below the tree line. The ski slopes at such resorts are created in one of two ways: chopping down trees, leaving small stumps that are covered by snow; and chopping down trees, removing the stumps, relocating any boulders and machine-levelling the ground.
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Jennifer Burt and Kevin Rice of the University of California, Davis, decided to examine the American system. They studied seven resorts of differing sizes close to Lake Tahoe in northern California and Nevada, all of which had most of their ski runs below the timberline. Dr Burt and Dr Rice surveyed the vegetation and soils on the different ski runs and then compared them to adjacent areas of nearby forest. To do this they designated large plots (some 20 metres by five metres) in which they counted how many plants were present as well as the number of species represented. They also measured soil compaction and erosion.
What they found was that the way in which the trails had been constructed accounted for nearly all the difference in the number of plants and the diversity of species present. Ski runs that were machine-graded and cleared of boulders and stumps tended to have small herbaceous plants growing on them and little else. Such growth is typical in regions of great environmental disturbance and usually represents the first steps in a region towards ecological recovery. The trails that had simply been cleared of trees were dominated by shrubs, which usually indicate terrain that is ecologically well developed. The difference in the amount of exposed bare ground was also dramatic: it accounted for an average 48% of ground cover on graded runs, and just 23% of cleared runs.
Soil differed markedly as well, with erosion on machine-graded slopes being significantly more severe than erosion on slopes that had simply been cleared of trees. Measurement of soil compaction, which is important for determining whether the soil is soft enough for plant roots to grow into, and how much water can be absorbed by it, found that the soil was twice as hard on graded runs than it was on cleared runs and untouched forests.
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In fact, far from finding that all ski trails are disturbed habitats, what Dr Burt and Dr Rice found was that tree-cleared ski runs are often much more similar to forests than they are to ski runs that have been machine-graded. Indeed, the researchers reckon that ski runs cleared of only trees offer some ecological benefits because they locally increase native species diversity and habitat variety without creating harsh boundaries that leave species near the forest edge exposed. They report their results in this month’s issue of Ecological Applications.
Although your correspondent notes that American-style skiing appears to be far more environmentally friendly than its Alpine counterpart, he cannot advocate Europeans crossing the Atlantic Ocean and, indeed, most of America itself for a ski holiday. Instead, any new ski runs on either side of the Atlantic Ocean and elsewhere should be created at relatively low altitudes and by tree clearance rather than machine-grading, a lesson that also holds true for firebreaks, power line rights-of-way and temporary access roads.
:SugarwareZ-113:
The most popular ski resorts in Europe are at high altitudes, where snow falls early in the season and, with luck, regularly throughout it. Most studies of the ecological impact of skiing have examined the ecological devastation caused by these resorts. However, few studies have examined the impact of skiing at resorts popular in the American west that are typically built at lower altitudes, below the tree line. The ski slopes at such resorts are created in one of two ways: chopping down trees, leaving small stumps that are covered by snow; and chopping down trees, removing the stumps, relocating any boulders and machine-levelling the ground.
Shutterstock
Jennifer Burt and Kevin Rice of the University of California, Davis, decided to examine the American system. They studied seven resorts of differing sizes close to Lake Tahoe in northern California and Nevada, all of which had most of their ski runs below the timberline. Dr Burt and Dr Rice surveyed the vegetation and soils on the different ski runs and then compared them to adjacent areas of nearby forest. To do this they designated large plots (some 20 metres by five metres) in which they counted how many plants were present as well as the number of species represented. They also measured soil compaction and erosion.
What they found was that the way in which the trails had been constructed accounted for nearly all the difference in the number of plants and the diversity of species present. Ski runs that were machine-graded and cleared of boulders and stumps tended to have small herbaceous plants growing on them and little else. Such growth is typical in regions of great environmental disturbance and usually represents the first steps in a region towards ecological recovery. The trails that had simply been cleared of trees were dominated by shrubs, which usually indicate terrain that is ecologically well developed. The difference in the amount of exposed bare ground was also dramatic: it accounted for an average 48% of ground cover on graded runs, and just 23% of cleared runs.
Soil differed markedly as well, with erosion on machine-graded slopes being significantly more severe than erosion on slopes that had simply been cleared of trees. Measurement of soil compaction, which is important for determining whether the soil is soft enough for plant roots to grow into, and how much water can be absorbed by it, found that the soil was twice as hard on graded runs than it was on cleared runs and untouched forests.
Click here
In fact, far from finding that all ski trails are disturbed habitats, what Dr Burt and Dr Rice found was that tree-cleared ski runs are often much more similar to forests than they are to ski runs that have been machine-graded. Indeed, the researchers reckon that ski runs cleared of only trees offer some ecological benefits because they locally increase native species diversity and habitat variety without creating harsh boundaries that leave species near the forest edge exposed. They report their results in this month’s issue of Ecological Applications.
Although your correspondent notes that American-style skiing appears to be far more environmentally friendly than its Alpine counterpart, he cannot advocate Europeans crossing the Atlantic Ocean and, indeed, most of America itself for a ski holiday. Instead, any new ski runs on either side of the Atlantic Ocean and elsewhere should be created at relatively low altitudes and by tree clearance rather than machine-grading, a lesson that also holds true for firebreaks, power line rights-of-way and temporary access roads.
:SugarwareZ-113: