AEC 360    Ecology

Lecture 6: The carbon cycle and global warming

I.  Global temperature is related to the level of atmospheric CO2
    A.  The greenhouse effect

II.  The carbon cycle
    A.  A critical part of all ecosystems, as life on earth is carbon-based

    B.  Carbon is absorbed into ecosystems mainly through plants

    C.  Carbon is lost into the atmosphere through respiration

    D.  Carbon also in soils, oceans, and fossil fuel

    E.  See Figure 21.3 for a description of the Carbon Cycle. 

III.  How have humans altered this cycle?
    A.  Pre-human industrialization, primary production and respiration roughly balanced

    B.  Humans now add ~7 Pg per year by burning of fossil fuels and vegetation

IV.  Ecological consequences
     A.  Because CO2 is essential for plant growth, rising concentrations may have ecological consequences

        1.  Testing for effects of CO2 at Duke Forest

        2.  Increased CO2 elevates the toxicity of Poison Ivy


    B.  Most of the ecological effects of rising CO2 arise due to effects on global warming
        1.  Plant and animal physiology
        2.  Species distributions
        3.  Timing of seasonal events
        4.  Species interactions

     C.  Effects of global warming on checkerspot butterfly distributions (Parmesan 1996)
       1.  --Censused butterflies in sites throughout its range
            --Documented where butterflies were found historically
            --More likely to disappear in southern latitudes
            --More likely to disappear at low elevations

        2.  Across 1400 species of plants and animals that have been evaluated, ranges have shifted on average:
            --17 kilometers/decade poleward
            --11m/decade upward in elevation

     D.  Climate change may affect seasonal timing of ecological events -- examples

      E.  Problem:  climate may be changing so fast that ecosystems cannot respond
            1.  Golden Toad and Monteverde Harlequin frog already driven extinct
            2.  On our current course, 7.7% of biodiversity will be lost

       F.  How climate change causes species extinctions

       G.  Climate change reduces crop production

       H.  Biodiversity must adapt to novel climates

       H.  Other physical effects of warming
            1.  Glacial loss and sea level rise

            2. Sunny Day Floods and loss of coastal environments

        H. Climate policy