The problem, according to Science Daily, is that marginal pastureland in the Swiss Alps, after 8 centuries, is being abandoned and given back to nature. So what does nature do? She grows green alder, which by increasing evaporated water causes a decrease in runoff feeding streams. These streams feed hydroelectric generators, and thus the reduced flow, in one valley alone, will cost something like 500,000 to 1,000,000 Swiss francs annually. The alder also “contaminates the water with nitrates,” tho the article doesn’t explain how this is a problem.
The remedy? Researchers demonstrated that Engadine sheep will peel the bark off the alder, killing them and [presumably] restoring grassland. But “the added financial value of sustainable land use is not sufficient to keep the arable land open.”
Which raises the interesting question: Which poor country has a sheep-raising tradition and potential emigrants who might like to move to Switzerland?