Beginning in the early 1970s , the Bureau of Land Management identified damaged riparian zones and began projects to restore natural habitat in those areas . Approximately 20 @,@ 000 willow trees were planted along streams , small dams were put together to create more pools in the streams , and fencing was added to protect riparian zones from grazing . Next , the agency sought to reform land @-@ use plans to change grazing practices , which became a complex and controversial project .