Vanishing Old-Growth Forest in the Pacific Northwest:

Deforestation is usually associated with activities in the
tropical rainforests of South America, but it can be seen to
be a serious problem in temperate zones of the Earth as
well. 

Clear-cutting of the late-successional or "old growth"
evergreen trees in the national forests of the  U.S. Pacific
Northwest is causing a high degree of habitat fragmentation.
Logging of these ancient forests has destroyed the
continuity of the forests; large portions of the forests
have been cut into small segments by roads leaving thousands
of juvenile tree farms of 40 to 60 acres.  This
fragmentation tends to destroy the habitats required by many
species of animals such as the spotted owl and native salmon.

Extensive mapping has shown that a little more than 10
percent of the original 25-million-acre forest that once
stretched from Northern California to the Canadian border is
now intact. This great swath of trees, including species
like the Pacific yew, which contains a cancer-fighting
compound, and many plants and animals in danger of being
lost forever, is generally considered the biggest and
richest of American forests.  

This image shows a portion of Mount Hood National Forest in
western Oregon.  Dark-red areas represent old growth;
light-red areas represent regrowth; and pink areas are
places where young saplings have appeared.  Blue areas
indicate lack of vegetation due to logging.

In accordance with  U.S. Forest Service policy, almost all
of the cut areas in the national forests have been replanted
with new trees, but this will not be apparent in satellite
images until the trees are about 2-3 years old.  

(Image and summary were extracted from The Earth Observing System
Educators' Visual Materials, 
http://spso.gsfc.nasa.gov/eos_edu.pack/p20.html)



Questions:

a. Give a rough estimate of the percentage of the total area of
the image that each type of surface covers: i)old growth,
ii)regrowth, iii)saplings and iv)recently clear-cut.

b. Forests are important not only for their role in maintaining
biological diversity but also because of their role in
global climate. How does clear-cutting change the albedo (and
therefore temperature)of this region?  How does the clear-cutting
effect the input of CO2 to the atmosphere? How may such a change,
if it were on a big enough scale, effect the global climate? 
(Think in terms of the "Greenhouse Effect," global warming, etc.)

c. Why do you think clear-cutting of old-growth forests effects
salmon?  [Hint: Think about changes in run-off, soil erosion,
changes in sediment input to rivers....]

d. To what biome does this forest belong?  (Refer to your vegetation lecture
handout to find a map of major biomes.)  How big of an area does this vegetation
type cover compared to the entire U.S.?  Do you think this plays
a role in why environmentalists are concerned about its
destruction?