I want to know the answer to the following question:
What has changed since the second half of the 20th century?
All the background I'm provided with is that "In some areas the modern practice of building ski runs by mechanical means has destroyed the underlying tundra from which the plant life cannot recover during the non-skiing months, whereas areas that still practice a natural piste type of ski slope building preserve the fragile underlayers.". Is that enough to answer the question?
Answer: no