How did the reintroduction of wolves impact the tree population in the park?

Data as of July 10, 2016. Today, nearly 25 years after wolves were reintroduced into the park, the top predators have helped parts of the ecosystem bounce back. They've significantly reduced elk herds, opening the door for willow, aspen, beaver and songbird populations to recover.

Explanation:

a- all cells come from pre-existing cells