Trophic cascade

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Trophic cascade by Mind Map: Trophic cascade

1. = ecological process that starts at the top of the foodchain and tumbles all the way down to the bottom

2. Example: the reintroduction of wolves to the Yellowtone national Park in 1995.

2.1. Wolves take lives

2.2. Wolves give life to many others

3. Wolves absent for 70 years

4. Number of deer built up (nothing to hunt them) (and despite human efforts to reduce their numbers)

4.1. The woves arrived

4.1.1. Small in numbers

4.2. Deer reduced vegetation to almost nothing (grazed it away)

5. Remarkable effects

6. Killed some of the deer

6.1. That wasn't the major thing

7. Changed the behaviour of the deer

7.1. more significantly

8. Deer started to avoid some parts of the park

8.1. The places where they caould be trapped most easily

8.2. Most particularly the valleys and the gorges

9. These places started to regenerate

9.1. In some areas the height of the trees quintupled in just 6 years

9.2. Bare valleysites quickly became forests of aspen and willow and cottonwood

10. The birds started moving in

10.1. songbirds and migratory birds

11. The number of beavers started to increase

11.1. like to eat the trees

11.2. Beavers are ecosystem engineers

11.2.1. They create niches for other species

11.2.1.1. The dams they build = habitat for otters, muskrats, ducks, fish, reptiles, amphibians

12. The wolves killed koyotes

13. Number of rabbits, mice increased

14. More hawks, weasles, foxes, badgers

15. Ravens and bald eagles came to feed on the carrion the wolves left

16. Bears fed on the carrion the wolves left

17. Bear population began to rise

18. The rivers changed

18.1. meander less

18.2. less erosion

18.3. channels narrowed

18.4. more pools formed

18.5. more riffle sections

19. Reason: regenerating forests stabilised banks

19.1. collapsed less

19.2. riverbeds more fixed in their course

20. Less erosion in valleys too

21. Conclusion: Wolves changed the ecosystem AND the geology