The correct answer is hunters.
In certain habitats hunters are responsible for maintaining population numbers of certain species. Overpopulation of some animals can lead to destruction of local vegetation, death of other animals, spreading of diseases, infestations etc. To maintain equilibrium hunters will cull the numbers of certain animals periodically.
It made shipping goods difficult
You're looking at an ancient sand dune. What this means is that the place used to be like a sandy desert, similar to those in Africa. That is because the composition of sand is mostly silica, which appears in the form of quartz.
The Savanna had rolling grassland and few, scattered trees
