Wash. Rev. Code § 84.34.010
The legislature hereby declares that it is in the best interest of the state to maintain, preserve, conserve and otherwise continue in existence adequate open space lands for the production of food, fiber and forest crops, and to assure the use and enjoyment of natural resources and scenic beauty for the economic and social well-being of the state and its citizens. The legislature further declares that assessment practices must be so designed as to permit the continued availability of open space lands for these purposes, and it is the intent of this chapter so to provide. The legislature further declares its intent that farm and agricultural lands shall be valued on the basis of their value for use as authorized by section 11 of Article VII of the Constitution of the state of Washington.
RCW 84.34.010