Wednesday, November 10, 2010

Trees Cause Global Warming?

The interaction of agents within the natural biosphere is extremely complex and multifaceted. The reductive approach employed by scientific inquiry is met with difficulty when applied to understanding these interactions. The article “Careful Where You Put That Tree” written by Elizabeth Svoboda for Wired magazine attempts to demonstrate this difficulty through framing scientific findings in a way that casts doubt on what are popularly considered to be established facts. Specifically, this article questions the application of trees in reducing the planet’s temperature, going so far as to argue that trees can in fact potentially warm the climate. Climate researchers are quoted several times throughout this article expressing a lack of commitment to any factual statement. This selective quotation creates the impression of a lack of scientific consensus regarding the interaction between trees and atmospheric temperatures. The article closes by invoking the precautionary principal, citing poor scientific understanding as a basis for not taking direct action to mitigate climate change.

Elizabeth Svoboda puts forth a recent discovery suggesting that trees warm the planet. The explanation of this phenomenon is that as sunlight hits trees this energy is stored and later released as heat. This interaction is vaguely described as having a warming effect overall. The discovery of this phenomenon is credited to Stanford University atmospheric scientist Ken Caldeira although no primary source article detailing this discovery is referenced. Whether these findings are valid or being accurately presented is questionable. However, even if one accepts that this phenomenon may occur it does not effectively support the argument that trees cause global warming when considered in a greater context. It is well established that urban areas become hotter than the surrounding areas because of the high degree of heat retained by asphalt, concrete and other urban infrastructure (Landsberg 1981). The urbanization of previously vegetated areas would have a greater effect on cumulative heat retention than any caused by trees. Even without considering the interaction between greenhouse gases and trees, the notion that trees cause global warming through retaining heat falls apart when one compares any heat that trees may retain to the heat retained by anthropogenic structures.

The article also credits Ken Caldeira with the creation of a computer simulation demonstrating that if northern latitudes were reforested to a serious degree, global temperatures would rise 6 degrees. However, one does not need to look to computer simulations for an example of global temperature in a situation where northern latitudes are mostly forested. These areas have been near totally forested in the past. As deforestation has progressed over the last several hundred years global temperatures have been rising over the same period. This observed trend is antithetical to the results of the simulation referenced. It must be noted of course that there are many factors affecting global temperature other than degree of forest coverage. It is difficult to develop an accurate concept of the relationship between land coverage and global temperature because neither variable can effectively be isolated in an experiment that would retain external validity. Despite this difficulty, it is certainly apparent that during a period of mass deforestation, global atmospheric temperatures have in this same period been increasing. This casts serious doubt on the premise that trees contribute to global atmospheric temperatures.

The intention of the article “Careful Where You Put That Tree” is apparently to demonstrate that there is great scientific uncertainty about nearly every aspect of the issue of global warming. Vague quotes are employed from various academics in the field of climate research that imply such uncertainty. For example, David Erickson, director of the Climate and Carbon Research Institute at Oak Ridge National Laboratory is quoted as follows, “It's very interesting that changing land use -- whether that means growing trees or cutting them down -- can have an effect on climate”. This quote makes no positive or negative statement regarding the interaction between trees and global temperatures, and is used in the context of this article to imply that no such relation is understood. The article employs this apparent lack of understanding in invoking the precautionary principal. This principal is suggested in a closing quote from Ken Caldeira, “Earth systems are very complicated… The less we interfere with the system, the more likely we are to have a healthy planet.” There is indeed truth to this statement however there is also a strong degree of naivety. It is true that interference with the natural system has in many cases led to unfortunate consequences. However, this interference has gone on for so long without regard for the precautionary principal that great damage to the environment has occurred. This damage will not be mitigated without further intervention to restore symbiosis between human activity and the non-anthropogenic biosphere. To consider the precautionary principal before taking action that will affect other beings is essential for a responsible entity. This article however suggests that the precautionary principal should be applied so strongly as to preclude action intended to mitigate previous human damages to our environment. Such philosophy is impractical at this epoch in human progression.

The belief that no understanding is infallible is central to the scientific dogma. However, this aspect of science is overemphasized in Elizabeth Svoboda’s article. By employing questionable studies and modeling, doubt is cast on the efficacy of planting trees as a strategy to mitigate global warming. It is important to respect that there are limits to scientific understanding. This must be kept in mind when considering action intended to reestablish natural systems of balance. However, such action is necessary at a point in human progress where prior and current activity has created phenomena such as climate change. Global warming is generally accepted to be a consequence of elevated levels of greenhouse gases in the earth’s atmosphere rather than of heat retention occurring on earth. The fixation of greenhouse gases such as carbon dioxide and nitrous oxide by trees is well known and trees are essential elements in removing such substances from the atmosphere. Although the precautionary principal should be kept mind at all times, it is a disservice to the global community to invoke it on the basis of questionable arguments suggesting uncertainty. This disservice is particularly acute when inaction poses a greater danger to the planet than simple actions such as planting trees ever could.

By Dylan Harding



Svoboda, Elizabeth. (2005, December 23). Careful where you put that tree. Wired.

Works Cited

Landsberg, H. E. (1981). The Urban Climate. New York: Academic Press.

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