The human impact in South America can be seen primarily in the destruction of the rainforests and the usage of the grasslands for ranching.
Because big portion of the South American continent is covered with rainforest, the countries are trying to boost their economies by using them, especially because there is lot of high quality, expansive timber for which there's big demand. Also, because of the growing population, more food is needed, so the forests are cleared in order to make space for the agriculture.
The grasslands are heavily used for ranching, and instead of them being dominated by wildlife, they are dominated with cattle, and that is disrupting the whole ecosystem.
