Trophic cascade
by Herr Lehrer
1. Wolves absent for 70 years
2. Number of deer built up (nothing to hunt them) (and despite human efforts to reduce their numbers)
2.1. The woves arrived
2.1.1. Small in numbers
2.2. Deer reduced vegetation to almost nothing (grazed it away)
3. Killed some of the deer
3.1. That wasn't the major thing
4. Changed the behaviour of the deer
4.1. more significantly
5. Deer started to avoid some parts of the park
5.1. The places where they caould be trapped most easily
5.2. Most particularly the valleys and the gorges
6. These places started to regenerate
6.1. In some areas the height of the trees quintupled in just 6 years
6.2. Bare valleysites quickly became forests of aspen and willow and cottonwood
7. The birds started moving in
7.1. songbirds and migratory birds
8. The number of beavers started to increase
8.1. like to eat the trees
8.2. Beavers are ecosystem engineers
8.2.1. They create niches for other species
8.2.1.1. The dams they build = habitat for otters, muskrats, ducks, fish, reptiles, amphibians