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Spotted Owl/ Old-Growth Forests



The case of the northern spotted owl points out why we need forest management focused more on ecosystem values than we've had in the past. Studies in Oregon show that this owl's population declined by a third between 1976 and 1987. The U.S. Forest Service estimates only 3,000 to 6,000 northern spotted owl pairs remain in North America. Each pair requires a range of 4,000 to 9,000 acres for hunting and foraging and can nest only in the broken tops of dead "old-growth" firs. Because the spotted owl was declared an endangered species, a court injunction halted most timber sales in national forests where old-growth firs are found. But the importance of the complex ecosystem of an old-growth forest extends far beyond the preservation of the spotted owl. Old-growth forests in the Pacific Northwest are full of ancient standing trees, fallen trees, snags, and decaying vegetation (fungi, lichen, and moss) which provide shelter and food to plants and animals that cannot live elsewhere. At least 118 known vertebrate species live primarily in old-growth forests; 41 of these species cannot nest, breed, or forage anywhere else. New-growth forests are managed monocultures--containing only a few species of trees that were planted at the same time. These areas do not offer the same habitat diversity for plants and animals. For example, only nine mammal species make their home in second-growth forests of young firs and hemlocks, compared to 25 in old-growth forests. The classic old-growth forests contain redwoods, cedars, Douglas fir, hemlock, or spruce. These forests have at least eight big trees per acre that are older than 300 years or more than a meter (40 inches) in diameter at breast height. Only 4.3 million acres of our old-growth forests remain, about one-third of it protected in designated national wilderness areas in parks. The loss of the old-growth Douglas fir is similar to the loss of the giant redwoods, originally the greatest old-growth forest on earth. Less than 4% of the giant redwoods still stand, mostly in roadside parks. Loggers, environmentalists, and scientists have started to hammer out a new form of forest management that protects the environment but attempts to endanger fewer jobs. A better understanding of the value of forests will help them arrive at a solution.


Trees grow both in height and in girth. The rings on the stump of a tree indicate how many years have passed in the tree's life. Spring wood can be recognized as light rings; summer wood as dark. One set of light and dark rings represents one year. Paleoclimatologists trace climatic changes and other disturbances by studying the ring patterns in old trees. Materials Obtain a variety of cut round sections from large tree trunks. A local tree service might provide pieces from different types of trees.
  1. Make a sketch of the flat cut face of each trunk, showing all the rings that appear.
  2. Count the number of rings across the surface of the trunk. (Count from the center out; do not count the bark.) This corresponds to the tree's age. Label each drawing.
  3. Post the sketches next to each other.
  4. Label the rings in your sketch to show several important historical events as well as major occasions in your life. Is the tree as old as you are?
  5. Measure each trunk's diameter.
  6. Research why some rings are farther apart than others. Remember that wide rings show periods of strong growth and narrow rings indicate adverse conditions. Questions
    1. Does the diameter of the tree always correspond with its age? Why or why not?
    2. What are the oldest trees in the world? In the United States?
    3. What environmental factors might have encouraged growth? What might have hampered the growth of the tree?
    4. Can you think of an environment where it would be difficult to determine the age of a tree because there were no growth rings?


  • Facklam, M. (1990) And then there was one. San Francisco: Sierra Club Books.
  • Future of forests. (1991, June 22) The Economist, pp. 19-23.
  • Gup, T. (1990, June 25) Owl vs. man. Time, pp. 56-63.
  • Kelly, D., & Braasch, G. (1988) Secrets of the old forest. Salt Lake City: Peregrine Smith Books.
  • Lovett, S. (1992) Extremely weird endangered species. Santa Fe, NM: John Muir Publications.
  • McDonald, T.B. (1990, Dec) End of an era. Architectural Record, pp. 40-41.
  • Satchell, M. (1990, June 25) The endangered logger. US News and World Report, pp. 27-29.