It is hereby declared to be in the public interest to encourage the preservation of historic agricultural structures which are potentially subject to decay or demolition, thus maintaining the historic rural character of the state‘s landscape, sustaining agricultural traditions, and providing an attractive scenic environment for work and recreation of the state’s citizens and visitors. It is further declared to be in the public interest to prevent the loss of historic agricultural structures due to property taxation at values incompatible with their preservation. The means for encouraging preservation of historic agricultural structures authorized by this chapter is the acquisition of discretionary preservation easements by town or city governments to assure preservation of such structures which provide a demonstrated public benefit.