Many people want to live in urban areas one of the main factors that limit the number of people that can live in an area is

limited resources

Explanation:

Resources like infrastructure, land, water, food etc are essential to stay in any area. With limited infrastructure services the living quality of an area degrades. Like wise non availability of resources like water, land (or very costly land due to high demand) also degraded the living condition in any urban area.

sheep is a herbivore animal whereas grasshopper belongs to the class chordates but both of them feed on greens.  

if grasshopper and sheep feeding on a pasture land, i do not think both of them will have any impact on each other. however, the number of the species can make difference. since sheep feed on greens, there is a possibility there left no pasture land for the grasshoppers or they may get extinct.