EFU and forest zoning decide the value
Oregon runs a statewide land use program under ORS chapter 197: the Land Conservation and Development Commission adopts statewide planning goals, and every city and county plan must comply. Goal 3 protects agricultural lands and Goal 4 protects forest lands, which counties implement through Exclusive Farm Use zones authorized by ORS 215.203 and comparable forest zones. Goal 14 keeps urban development inside urban growth boundaries. In an EFU or forest zone a dwelling is not a use you can assume — it is an approval you have to earn under a narrow statutory pathway. Acreage does not qualify you. A hundred acres of EFU ground with no dwelling right is worth less than a small parcel that has one.