(1) All real property interests, including fee simple or any lesser interest, development rights, easements, covenants and conservation futures, as that latter term is defined in RCW
84.34.220 as now or hereafter amended, used exclusively for the conservation of ecological systems, natural resources, or open space, including parklands, held by any nonprofit corporation or association the primary purpose of which is the conducting or facilitating of scientific research or the conserving of natural resources or open space for the general public, shall be exempt from ad valorem taxation if either of the following conditions are met:
(a) To the extent feasible considering the nature of the property interest involved, such property interests shall be used and effectively dedicated primarily for the purpose of providing scientific research or educational opportunities for the general public or the preservation of native plants or animals, or biotic communities, or works of ancient human beings or geological or geographical formations, of distinct scientific and educational interest, and not for the pecuniary benefit of any person or company, as defined in RCW
82.04.030, and shall be open to the general public for educational and scientific research purposes subject to reasonable restrictions designed for its protection; or
(b) Such property interests are subject to an option, accepted in writing by the state, a city or a county, or department of the United States government, for the purchase thereof by the state, a city or a county, or the United States, at a price not exceeding the lesser of the following amounts: (i) The sum of the original purchase cost to such nonprofit corporation or association plus interest from the date of acquisition by such corporation or association at the rate of six percent per annum compounded annually to the date of the exercise of the option; or (ii) the appraised value of the property at the time of the granting of the option, as determined by the department of revenue or when the option is held by the United States, or by an appropriate agency thereof.
(2) To be exempt under this section, the property must be used exclusively for the purposes for which exemption is granted, except as provided by RCW
84.36.805.