Guns, forests and carbon

Not only do humans burn away forests to enhance their food supply, they also do it when they battle each other! Or so says a study published by Zhen Li and his colleagues this week in the Proceedings of the National Academy of Sciences (Li et al. 2009). By linking a careful investigation of paleoclimate indicators from sediments with burning estimates from charcoal in these same sediments and the archaeological and historical records for Northern Vietnam over the past 5000 years, it was determined that the burning of forests was greater during periods of instability than during periods of relatively stability, when agricultural clearing of forested lands are thought to have been greatest.

Is this just the tip of the iceberg? For a long time, it has been believed that environmental conditions have helped induce and exacerbate human conflicts (e.g. Homer-Dixon 1991), and even the collapse of entire civilizations (e.g. Diamond 2004). But are wars and other human conflicts a major cause of global change in the biosphere and climate over the long term?

Whether or not wars are more influential on earth systems than workaday land use for agriculture, the evidence continues to grow that humans are in the driver’s seat when it comes to global climate and the shape of the biosphere. One more reason to stop fighting and start working together to make our planet what we want it to be!

References
Diamond, J. 2004. Lessons from Environmental Collapses of Past Societies. In “Fourth Annual John H. Chafee Memorial Lecture on Science and the Environment.” pp. 40. National Council for Science and the Environment, Washington, DC. < link to online document>

Homer-Dixon, T. F. 1991. On the Threshold: Environmental Changes as Causes of Acute Conflict. International Security 16, 76-116. http://www.jstor.org/stable/2539061

Li, Z., Saito, Y., Dang, P. X., Matsumoto, E., and Vu, Q. L. 2009. Warfare rather than agriculture as a critical influence on fires in the late Holocene, inferred from northern Vietnam. Proceedings of the National Academy of Sciences 106, 11490-11495. Read the article (free and open): http://www.pnas.org/content/106/28/11490