Write ONE WORD ONLY for each answer.
Trophic cascade: An ecological phenomenon occurs when an animal at the top of the food chain affects at the bottom.
Before reintroduction, wolves in Yellowstone Park had been for 7 decades.
The increased numbers of deer had resulted in the reduction of in the park.
With wolves returning, things started to change.
The deer changed their to avoid wolves in some areas of the park.
This caused those areas to regenerate.
It also resulted in some trees growing five times in in just six years.
The number of birds and began to increase.
Their dam building habits provided for ducks, fish and reptiles.
The of regenerating trees and plants prevented soil erosion.
An increase in the number of was significant for wildlife habitats.
So, the wolves changed both the and physical geography of Yellowstone Park.
BestMyTest IELTS listening Report
Score Summary 
Submit your listening answers to auto generate this report.