A. Introduction
    B. Objectives
    C. Methodology
    D. A STELLA Model of the Carbon Cycle
    E. Results and Conclusions
    F. Bibliography
    G. National Professional Development Standards

II. Transferring to the Classroom
        a.  National Content Standards
 
IV. The Group

    Human activities directly influence both the structure and function of forests on a global
scale.  Forests in the United States exhibit a regional growth pattern that are a consequence of their past use by humans.  About three-quarters of U.S. forest covered the eastern third of the country in 1600; about three-quarters of the forest is also in the East today. The original forest covered 1.1 billion acres (about half of the U.S. area).  Today there are 730 million acres of forest, about two-thirds of the original forest (Mac Cleery, 1992).  About 370 million acres have been converted to other uses since 1600 , primarily to agricultural lands.
    The U.S. forest landscape has changed greatly over time.  The creation of a settler empire of over two million people on the eastern seaboard of North America left an imprint on the forest (Williams, 1990).  Over the past 150 years, since the onset of the industrial revolution, as human population increased, there was a corresponding increase demand for food, shelter and energy.  Although the deforestation for agricultural use has been emphasized in literature, it should also be recognized that timber was also used for housing, fencing, furniture, other wood products and fuel.  While agricultural use was the predominant use originally that use has stabilized with urban, industrial and recreational use continuing to increase.  Most of the pre-settlement forest has now been cleared except for pockets in the western U.S.  At the end of the 20th century, values of global significance are increasingly being attributed to forests.  One such attribute is its ability to accumulate atmospheric carbon (Apps, and Price, 1994).
    It is generally agreed that deforestation initiates local changes, but there are varying opinions as to the likely effect of deforestation on the global hydrological cycle and global climatic change (Salati and Vose, 1983).  Deforestation on a global scale since 1890 has greatly contributed to the total release of carbon.  Some estimates put deforestation at about 23 percent of the total contribution of carbon dioxide (Liverman and Solem, 1996).
    Carbon dioxide is one of the most important greenhouse gases and is responsible for about 60 percent of the enhanced greenhouse warming.  Its atmospheric concentration has increased tremendously since the industrial revolution (World Resources Institute, 1994).  However, at present carbon dioxide content in the atmosphere seems to be increasing primarily due to increased use of fossil fuels.

OBJECTIVES:

     The purpose of this project was to examine the effects of human activities such as deforestation over 400 years and increased fossil fuel burning in the United States on the carbon cycle.

METHODOLOGY:   (to top)

    In order to explore the effects of deforestation in the United States, research was done in the areas of deforestation over four hundred years as well as fossil fuel burning.  Research involved the consultation of several written resources listed in the references.  We received valuable materials from Mr.  Gerard Hertel and Richard Birdsey, both from the USDA Forest Service (Radnor, Penn.).  We also appreciate the suggestions of Bill Summers (USDA Forest Service, Washington, DC.), Jim Berresi (New Jersey State Forestry Service), Mark Twery (Burlington, Vt.), and Dr. John Kuser (Rutgers University).
    We used John Snow's Stella sector model for the global carbon cycle in order to examine and display the response of the cycle to deforestation and fossil fuel burning.  The model used, patterned after that of Bolin (1981), is a representation of those portions of the carbon cycle operating on time scales of seasons to several centuries.  This model focuses on the very short-term atmosphere-terrestrial biosphere loop and the limited interaction between atmosphere and ocean.

 

    Comparison of the results of two different scenarios with low and high fossil fuel consumption with deforestation as noted above revealed a similar pattern (carbon dioxide in the atmosphere and GMT rising slightly between 1750-1950). Our graphs also showed that increased fossil fuel consumption resulted in a very progressive and  rapid increase in atmospheric carbon dioxide and GMT between 1950 to 2050 (see graphs 2 and 3). In the scenario of low fossil fuel consumption it is interesting to note that with the distinct increase in atmospheric carbon dioxide and corresponding increase of GMT starting around 1900 there was a leveling off of carbon dioxide in the atmosphere around 2040 (see graph 2 ).  This is probably the result of the response of the forest as a carbon sink.
 
 

 

    We also tested two other scenarios testing deforestation as opposed to reforestation from 1980 to 2050 (with fossil fuel consumption remaining the same).  Analysis of the graphs indicated a sharp increase in atmospheric carbon dioxide and GMT in the deforestation scenario with atmospheric carbon dioxide and GMT beginning to recover in the reforestation scenario (see graphs 4 and 5).
     Based on analysis of our results from the model, we believe that continuing emissions of carbon dioxide at present rates may result in an increased  carbon dioxide concentrations for at least the next century.

 

    The potential trends of carbon pools and net carbon fluxes in U.S. forests  are of  interest to determine how long and to what extent they will continue to act as net carbon sinks.  Some authors suggest that the United States forests have been significant carbon sink since 1952 and additional carbon accumulation will likely occur through 2040, but at a slower rate.  Between 1952 and 1992, carbon stored on United States forest land increased by 11.3 billion metric tons, an average of 281 million metric ton for each year, and an amount that offset about one quarter of the United States emissions of carbon for the period (USDA Forest Service Report, 1995).
     Available data show that forest ecosystems in the U.S. contain approximately 57.8 billion tons of carbon above and below the ground.  This is about four percent of all the carbon stored in the world's forests (Ajtay and others, 1979).  The largest proportion of carbon in the average U.S. forest is found in the soil (59%).  About nine percent of all carbon is found in litter, humus, and coarse woody debris on the forest floor, and about one percent is found in understory vegetation.  Trees, including tree roots, account for 31% of all forest carbon (Birdsey, 1992).  A comparison of accumulation and removal of carbon suggest that U.S. forest trees are storing additional carbon at a rate of 117 million tons per year.  This is an equivalent to about nine percent of the annual global emission of carbon to the atmosphere (Boden et. al., 1990).
    It is also well known that emissions resulting from human activities, are substantially increasing the atmospheric concentrations of carbon dioxide (Houghton and Scale, 1990).  Undeniably carbon dioxide has steadily increased on a global basis, probably since the 1860's, and at an accelerated rate since the end of World War II (Landsberg, 1996).  Systematic global measurements started during the International Geophysical Year 1957/1958.  Since then carbon dioxide concentration has risen about seven percent.  The total increase since 1860 has been from 280 ppm (parts per million per volume) to 335 ppm.
     The atmospheric carbon dioxide increase may enhance the greenhouse effect, resulting in additional warming of the Earth's surface.  There is general agreement that the infrared-absorbing qualities of carbon dioxide will reduce the outgoing radiation from earth to space and does increase the surface temperature. However, there is no agreement on the question of GMT rise (how much, how soon, and with what regional distribution).   Increasing carbon dioxide concentrations will  influence the forest ecosystems and forest ecosystems will subsequently affect climate.  Bolin (1981) pointed out that the regional biogeochemical processes, especially the carbon cycle, are important for climatic model and have so far been inadequately studied.  In conclusion, we would like to suggest several methods of dealing with current issues involving the carbon dioxide emissions to the atmosphere:
    1.  Be receptive to the possibility that global warming may exist and may worsen
    2.  Recognize the necessity of more scientific research
    3.  Explore and implement plans to reduce fossil fuel emissions.
        a.  Renew the search for safe/clean alternatives to fossil fuels
        b.  Encourage use of public transportation
        c.  Use tax reductions to encourage reduction of energy consumption
        d.  Develop and enforce minimum efficiency standards for appliances, buildings, etc.
        e.  Allow loans for energy efficient projects
    4.  Report the results of scientific research and, if warrented, press for international
        cooperation in managing our resources for reducing air pollution
    5.  Slow deforestation and implement a reforestation plan
 
 

 
 
        Ajtay. L. L., Ketner, P.,  and Duvigneaud, P. 1979. Terrestrial Production and Phytomass. In Global Carbon Cycle.  eds. Bolin, B., E. T. Degens, S. Kempe, and P. Ketner. Scope Report No. 13m 129-181. New York: John Wiley and Sons.

           Apps, Michael J. and David T. Price, ed. 1996.  Forest Ecosystems, Forest Management and the Global Carbon Cycle. New York: Springer.

   Birdsey, R. A. 1992a.  Carbon Storage and Accumulation in the United States Forest Ecosystems.  Gen Tech. Rep. WO-59. Washington, D.C.: U.S. Department of Agriculture, Forest Service. 51p.

        Boden, Thomas A., Paul Kanciruk,  and Michael P. Farrell.  1990.  Trends '90-A Compendium of data on Global Change. Oak Ridge National Laboratory, ORNL/CDIAC-36. Oak Ridge, TN. 257 p. + app.

        Bolin, B. ed. 1981. Carbon Cycle Modeling. Scope 16. New York: John Wiley and Sons.
 
         Heath, Linda S. and Richard A. Birdsey. 1993. Carbon Trends of Productive Temperate Forests of the Coterminous United States.  In Water, Air, and Soil Pollution 70.
Netherlands: Kluwar Academic Publishers. 279-293.

      Houghton, R. A. and David L. Skole. 1990. Carbon. In Earth as Transformed by Human Action. ed. B. L. Turner II, William C. Clark, Robert F. Kates, John F. Richards, Jessica T. Matthews, and William B. Meyers.  Cambridge: Cambridge University Press. 393-408.

         Joyce, Linda A. ed. Sept. 1995. Productivity of America's Forests and Climate Change.  Gen. Tech. Rep. RM-271.  Washington, D.C.: U.S. Department of Agriculture, Forest Service. 8p.

        Landsberg, H. E. 1986. the Greenhouse Effect is Exaggerated. In Is There an Environmental Crisis: Opposing Viewpoints. 45-50.

        Liverman, D. and Solem M. 1996.  The Geography of Greenhouse Gas Emissions.  Module Developed for the AAG/CCG2 Project by the Association of American Geographers. 22-24.

        MacCleery, Douglas W.  1992.  American Forests--A History of Resiliency and Recovery.  Gen. Tech. Rep. FS-540. Washington, D.C.: U.S. Department of Agriculture, Forest Service. 53p.

        Williams, Michael. 1990. Forest.  In Earth as Transformed by Human Action. ed. B. L. Turner II, William C. Clark, Robert F. Kates, John F. Richards, Jessica T. Matthews, and William B. Meyers.  Cambridge: Cambridge University Press.

    World Resources Institiute and International Institute for Environmant and Development (WRI/IIED). 1994. World Resources. New York: Basic Books.