Answer:
fenced off land
agriculture
introduction of sheep and cattle
excessive hunting
Step-by-step explanation:
These are all factors that the pioneers introduced to the prairies and which forever changed the natural environment of the region. The pioneers brought with them sheep and cattle, as they considered these necessities to sustain their way of life. However, these were new introductions to the area and required the land to be fenced in order to keep them from leaving. To sustain themselves, they also relied on agriculture and hunting. Agriculture changed the ecosystem of the area, as well as its appearance. Hunting was eventually done to an excessive degree, leading to the decline of many species, such as the American bison.