Scientists have noted a decline in the number of all mushroom species dating back to the early 1900s. in addition, annual crops of edible mushrooms in france and germany have declined since 1950. one hypothesis explaining the decline is that edible fungi are being overharvested. global warming and air pollution have also been considered as part of the problem. what evidence to exclude overharvesting as the cause of the overall decline? a) a similar decline in edible north american mushrooms b) absence of mushrooms near coal-burning powerplants in indonesia c) increase in mushroom species in a region of tropical south america d) declines in poisonous, non-edible mushroom species in cool climates