Your Name: GEO 300 TA-1
Your ID Number: 9xx-xxx-xx4
Recitation Time: 10:00 AM
TA Name: GEO 300 TA
Question Number: 1-11
Word Count: 549
Current deforestation rates exacerbate positive feedback loops that result in global warming
Interpretation (36 words)
Rates of deforestation have direct implications for atmospheric concentrations of carbon dioxide
(CO2). CO2 emissions, in turn, contribute to the global warming cycle. Clearing and burning forests
thus fuels a dangerous cycle of negative climate changes.
Analysis (405 words)
There are two ways in which deforestation can impact the amount of CO2 in the atmosphere. To
begin with, burning trees to clear a forested area releases greenhouse gases. Similarly, harvesting
trees generally involves heavy equipment powered by fossil fuels. Secondly, intact forests represent
an important sink in the carbon cycle. During photosynthesis, trees take in CO2 from the atmosphere.
As a result, forests have high carbon sequestration potential. (Tubiello et al., 2015: p. 2655). Hence
deforestation simultaneously increases CO2 emissions while decreasing the planet’s ability to uptake
existing CO2.
Rising concentrations of CO2 drive the global warming cycle. According to the IPCC, average
surface air temperature is predicted to increase 1.4–5.8 °C by 2100 (Houghton et al., 2001: p. 13).
This change will adversely impact the health of existing forests. Not only will the growth of certain
tree species diminish, but tree mortality rates will increase (Vose, Peterson & Patel-Weynand, 2012:
p. iv). Furthermore, the incidence and size of wildfires is predicted to increase. For example, a model
for the Western United States predicts that weather conditions linked to erratic and extreme wildfire
behavior will occur with increasing frequency (Luo, Tang, Zhong, Bian & Heilman, 2013: p. 2410).
As long as warming trends persist, the trees in our remaining forests will continue to be subject to
environmental stressors and will be at an elevated risk for disturbances such as wildfires.
Efforts to plant trees and convert agricultural land back to forested areas are unlikely to halt the
positive feedback loop driven by past deforestation. The Kyoto Protocol, which has been in effect
since February of 2005, offers carbon credits to organizations that successfully promote carbon
sequestration through afforestation projects. Converting agricultural land to tree plantations, for
example, has the potential to create a net carbon sink (Saurette, Chang & Thomas, 2008: p. 623).
However, even with maximum afforestation efforts, climate change models only predict a drop of 40
to 70 ppm in atmospheric levels of CO2 by 2100 (House, Prentiece & LeQuere, 2002: p. 1047). It is
important to note that pre-industrial levels of CO2 measured 280 ppm. At present, CO2 is found in
our atmosphere at concentrations of 370 ppm. Even in the extreme and improbable case of
reforesting all previously deforested areas, atmospheric CO2 concentration would only drop to 320
ppm at best (House et al., 2002: p. 1048). Reforestation efforts alone cannot break the positive
feedback cycle of global warming.
Evaluation (28 words)
Studies predicting the impact of deforestation on climate change rely primarily on mathematical
models with built-in assumptions. Depending on the given initial conditions, projected results can
vary widely.
Inference (20 words)
Afforestation provides global benefits, yet the economic cost and political risk factors associated
with tree planting efforts vary by country.
Explanation (40 words)
Deforestation has placed our planet into the positive feedback loop of global warming. While
reforestation projects have the potential to decrease atmospheric CO2 concentration, even extreme
efforts cannot restore CO2 levels to a point sufficient to break the warming cycle.
Self-regulation (18 words)
My background in the sciences leads me to trust mathematical models and accept the work of climate
scientists.
Literature Cited
Houghton, J. (Ed.). (2001). Climate change 2001 : the scientific basis : contribution of Working
Group I to the third assessment report of the Intergovernmental Panel on Climate Change.
New York, NY: Cambridge University Press.
House, J., Prentice, I. C., & LeQuere, C. (2002). Maximum impacts of future reforestation or
deforestation on atmospheric CO2. Global Change Biology, 8, 1047-1052. doi:
10.1046/j.1365-2486.2002.00536.x
Luo, L., Tang, Y., Zhong, S., Bian, X., & Heilman, W. (2013). Will Future Climate Favor More
Erratic Wildfires in the Western United States. Journal of Applied Meteorology and
Climatology, 52 (11), 2410-2417. doi: 10.1175/JAMC-D-12-0317.1
Saurette, D., Chang, S., & Thomas, B. (2008). Land-use conversion effects on CO2 emissions: from
agricultural to hybrid poplar plantation. Ecological Research, 23 (3), 623-633. doi:
10.1007/s11284-007-0420-x
Tubiello, F., Salvatore, M., Ferrara, A., House, J., Fererici, S., Rossi, S.,…Smith, P. (2015). The
Contriutio of Agriculture, Forestry and other Land Use activities to Global Warming, 19902012. Global Change Biology, 21 (7), 2655-2660. doi: 10.1111/gcb.12865
Vose, J., Peterson, D., & Patel-Weynand, T. (Eds.). (2012). Effects of climatic variability and
change on forest ecosystems: a comprehensive science synthesis for the U.S. forest sector.
Report prepared for United States Department of Agriculture, Pacific Northwest Research
Station, Portland, Oregon.