Found this on the Skagit county web site.
RCW Chapter 84.34 provides special consideration to property owners wishing to have land assessed for taxation purposes on the basis of its current use rather than its fair market value. The Open Space Act provides for current use appraisal of farm and agricultural land, timberland and open space land. Applications for classification are made to the Assessor for farm and agricultural land and to the county legislative authority for open space and timberland. Once land is classified, taxes are based on the current-use value rather than highest and best use. The Assessor must maintain the current use value for as long as the property remains classified. At the same time, a record of the fair market value of the property is kept. The difference between the current-use value and the fair market value becomes the basis for computing the amount of additional taxes, penalties and interest that may become payable upon a change of use or removal from classification.
http://dor.wa.gov/docs/pubs/prop_tax/openspace.pdfOpen space land is defined
as any of the following:
2. Any land area in which the
preservation in its present use
would:
a. Conserve and enhance natural
or scenic resources.
b. Protect streams or water supply.
c. Promote conservation of
soils, wetlands, beaches or
tidal marshes. (As a condition
of granting open space
classification, the legislative
body may not require public
access on land classified for
the purpose of promoting
conservation of wetlands.)
d. Enhance the value to the public
of neighbouring parks, forests,
wildlife preserves, nature
reservations or sanctuaries
or other open space.
e. Enhance recreation
opportunities.
f. Preserve historic sites.
Timber land is defined
as the following:
Any parcel of land five or more acres
or multiple parcels of land that are
contiguous and total five or more
acres which is or are devoted primarily
to the growth and harvest of timber
for commercial purposes. Timber land
means the land only and does not
include a residential homesite. The
term includes land used for incidental
uses that are compatible with the
growing and harvesting of timber but
no more than 10 percent of the land
may be used for such incidental uses.
It also includes the land which
appurtenances necessary for the
production, preparation, or sale
of the timber products exist in
conjunction with land producing
these products.
How does a public benefit
rating system work?
If the county legislative authority has
established a public benefit rating
system (PBRS) for the open space
classification, the criteria contained
within the rating system govern the
eligibility of the lands described in
each application filed for that
classification and the current use
valuation of that land.
When a county creates or amends
a PBRS, all classified open space land
will be rated under the new system.
A parcel that no longer qualifies for
classification will not be removed
from classification, but will be rated
according to the PBRS. Within 30 days
after receiving notification of the new
value established by the PBRS, the
owner may request removal of
classification of the parcel without
imposition of additional tax, interest,
and penalty