After 1995, the growth of willows increased in parts of Yellowstone, identify a possible cause for this trend. 1.Increase in the wolf population, decreased the elk population, which increased the willow population.

2.Increase in wolf population directly increases the willow population.

3.Increase in wolf population, increased the elk population, which increased with willow population.

4.Increase elk population created more feces (poop) to fertilize and increase the willow population.