What effects do herding in East Africa and ranching in North America have on those two environments?

Answer 1

http://allafrica.com/stories/201204110923.html

http://books.google.com/books?id=9KqDZ-TEGeAC&pg=PA130&lpg=PA130&dq=environment+herding+in+East+Africa&source=bl&ots=DILn4UuFLw&sig=iz6rrLmcDwM0nJ5ElOg4WKz5bZQ&hl=en&sa=X&ei=7funT6_jJ5K-gAeB0tHVAQ&ved=0CF4Q6AEwBA#v=onepage&q=environment%20herding%20in%20East%20Africa&f=false

http://www.msnbc.msn.com/id/46191566/ns/us_news-environment/t/great-migration-texas-cattle-heading-north/#.T6f88-g7XfE

http://www.nature.org/ourinitiatives/regions/northamerica/unitedstates/colorado/index.htm