Human land use is at once responsible for the very existence of the western Washington
prairies of the Puget trough and for their extensive degradation. Lessons learned from
studying the results of various land uses may point the way to recovery of the prairies
to something approximating their pre-1800 condition. Native American land use is
likely responsible for existence of the prairies and for much of their character. Their
manipulation of the land included frequent use of fire, along with various techniques
for cultivating native plants. Their use of fire retarded the advance of conifers onto the
open plains. Agricultural techniques may have been responsible for some of the
distribution of native plants and perhaps even for introduction from the interior of food
plants now thought to be native. Later arrivals have used the land in a greater variety
of ways, many of which have been destructive of traditional prairie characteristics.
Among the most destructive have been the suppression of fire and the introduction,
both intentional and accidental, of plants which have out-competed native prairie
vegetation. Other destructive uses include accelerating development, introduction of
livestock and allowing it to overgraze, draining of former wetlands, and various
military training activities. Establishment of Fort Lewis in 1916 likely retarded the
destruction by ending development on the prairies. Various mission changes have had
varying impacts on the prairies, but the overall result is easy to see in many places,
where subdivisions have begun to arise outside installation boundaries, and where
continued heavy grazing has caused displacement of native grasses. Fort Lewis
authorities have in recent years begun to reintroduce the use of fire in the prairies as
means of controlling Scotch broom. Some incidental consequences may include the
retardation of conifer invasion and suppression of other invasives that are not adapted
to cyclic burning.
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