Pressure Drop

My daughter has maintained from a very young age that trees make wind. Which is understandable for the childmind since one cannot see wind, only its repercussions in the trees. Waving branches, shaking leaves. Thus the most noticeable effect is conflated with the likeliest cause. But turns out she may be right.

In 2007, two Russian physicists, Victor Gorshkov and Anastassia Makarieva, put forth the “biotic pump theory” which postulates that forests, not temperature differentials, are the driving force behind wind patterns and, in turn, precipitation over land masses. A recent interview with these physicists can be found on Mongabay.com. http://news.mongabay.com/2012/0201-hance_interview_bioticpump.html

The biotic pump theory transcends conventional meteorology while further emphasizing the vital functions of forests in climate change mitigation. In the wind-generating forests of this still controversial model, water vapor from coastal forests and oceans turn to clouds. As the gas changes to liquid, the air pressure is lowered. The low pressure over the forest sucks moist air in from over the ocean generating wind, which drives moisture further inland. 

In terms of climate change, Victor Gorshkov and Anastassia Makarieva argue that it is the preservation of the water cycle over land – through the preservation of forests - that will have an even greater stabilizing effect than reducing carbon emissions. They say in the interview that, “Such climate stabilization can be performed by natural forests that control the hydrological cycle on land and the adjacent ocean, provided they are allowed to occupy a significant area. Conversely, destruction of forests leads to disruption of the hydrological cycle, which expectedly causes significant fluctuations of the magnitude of the global greenhouse effect, up to complete loss of climate stability and transition of Earth’s climate to a state incompatible with life.”

Given that the distinct interactions between forests and weather are the results of epic years of evolution, this proposed biotic pump functions most optimally in natural forest communities, and not monoculture plantation. In an intact ecosystem, “The root system of forest trees facilitates both storage and extraction of moisture from soil; biogenic aerosols produced by trees control the intensity of water vapor condensation over the forest; the large height of trees determines the vertical temperature gradient under the canopy, keeping soil evaporation under biotic control . . . Thus, natural forests not only create an ocean-to-land moist air flow, but also stabilize this flow at an optimum level and prevent its extreme fluctuations like hurricanes, tornadoes, severe droughts or floods.”

The critical role forests play in terms of carbon emission and sequestration is already situated at the heart of the climate debate. But if forests are also directly responsible for climate stability, the implications for global policy are vast. Take a look at the interview, reader, and tell us what you think.