How can rangeland be degraded?
Overgrazing is a problem if people do not obey allocation (by nature). Overgrazing should be protected by scientific rules to protect rangelands. Yes you benefit by grazing but do not harm your rangeland at the same time.
Another problem could be pollution (acidification due to acid rain, for instance) might make rangelands useless.
Converting grazing lands into urban or mining areas is another problem.