Political.
Given that historically the land (and lives) of many indigenous peoples was taken for grazing.
The history of Native Americans is well known. The bison were exterminated, in part, to create and maintain a dominant “cattle culture” across the Great Plains and the West—and, unfortunately for Native Peoples and wildlife—it worked. http://www.buffalofieldcampaign.org/about-buffalo/buffalo-and-native-americans
Australian indigenous people suffered a similar fate. In the face of continuing resistance, and justifying their actions by a belief in the superiority of their civilisation, the colonisers pushed Aboriginal people off the fertile lands into controlled settlements. http://www.clc.org.au/articles/info/the-history-of-the-land-rights-act/