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People need clean water. In the
western United States, almost all municipal waterthe stuff
we city-slickers usecomes from forests. About 70% of these
same forests are also actively managed for timber harvest.
Thus far, municipal water quality has been sustained while
other forest uses, logging and recreation for example, have
also been sustained. With a growing population in the West,
can we keep it up?
Fish need clean, cool water.
Fish and other aquatic animals, are not limited to the forested
reaches of waterways. Salmon, for instance, use waterways
to travel from the highest reaches, the often-forested mountains
where adults spawn, all the way to the oceans where juveniles
grow to adulthood. Because animals like salmon use all stretches
of waterways, it will take more than forest-covered mountains
to keep our streams healthy for them. Every stretch of riverwhether
in the mountains, in agricultural valley-lands, in the city,
or along the coast is important in maintaining water quality,
forested or not!
Trees play an important role in our
waterways. Fish need cool, oxygen-rich water in order
to survive and stay healthy. Trees help shade waterways,
keeping the water temperature down and the dissolved oxygen
high. Also, sediments washed into waterways from adjacent
land can coat the bottom of streams where fish lay their
eggs, suffocating them before they can hatchtree roots
can stabilize river banks, reducing erosion of sediments
into the stream. Tree roots can also regulate the flow of
water in the groundthis water can move more slowly through
the soil, giving microorganisms like fungi and bacteria
a chance to degrade pollutants before they reach the waterway!
Similarly, tree leavesboth green leaves in the tree canopy
and fallen leaves on the forest floorabsorb the impact
of raindrops, protecting easily eroded soil surfaces.
Because trees can play such an important
role in maintaining water quality, many times we can often
minimize water quality problems by "buffering"
a waterway from harmful impacts. In some cases we do this
by leaving borders of trees and understory vegetation; we
call these "buffer strips".
Buffer strips are successfully used
to reduce negative impacts on riparian
areas in a variety of circumstances. In fact, one can
see them along streams in agricultural, urban, and forested
areas. They are used as filters for animal waste-rich
waters that percolate from pasture. They are used as live
barriers to keep livestock away from sensitive areas like
easily eroded streambanks They are used to provide myriad
benefits to forested areas adjacent to fish-bearing streamstrees
are still harvested from upslope stands, but the valuable
services of streamside trees and other plants are maintained.
As you can see, trees and other plants
are important factors in water quality. Woody vegetation
like trees offer something else that few other plants can
however; large woody debris. Woody debris in streams creates
slow spots in fast-moving water where fish can rest. It
creates pools where fish can grow and escape predation.
Woody debris becomes both home and food for insects that
make up a fish's diet. It also provides fish the physical
cover needed to avoid predators. And, as mentioned before,
it can serve as a filter
for pollutants and sediments by acting as a biological "scrub-brush"
for the water!