Beavers can be the good guys helping nature. But sometimes not so helpful in other ways. Damage caused by beaver usually consisted of flooded timber and agricultural land, girdling and cutting valuable trees and interference with drainage systems. A 1975 survey of county Extension agents indicated beaver were responsible for about $3 million in damage statewide that year (University of Arkansas Cooperative Extension Service, unpublished report). Ten years later, estimates from a 1985 survey of landowners owning > 2 ha indicated beaver damage cost as much as $23 million annually (Wigley and Garner 1987). Most respondents (90%) to the survey agreed that government agencies should provide some services to landowners experiencing beaver-related problems. 

https://www.uaex.edu/publications/pdf/FSA-9085.pdf

http://wdfw.wa.gov/living/beavers.html

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