“Smelling the forest"

Press release, Cambridge, Massachusetts, December 22, 2020. 

Tropical forests directly release important compounds previously thought to be produced only by chemical reactions in the atmosphere. The work changes our understanding of the feedback among ecosystems, climate, and human pollution in the Amazon forest. Previously, pollution from combustion and transportation of oxides of nitrogen was expected to shift atmospheric chemical pathways in ways that decrease low-volatility semivolatile oxygenated organic compounds (SV-OVOCs). These compounds are precursors to atmospheric particles where clouds form, so the sequence of events can affect rainfall patterns and ecosystems. However, in the work reported today by a group of researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences, forests are found to emit important SV-OVOCs, specifically a family of compounds called 2-methytetrols, in large amounts. In this case, the natural ecosystem might have a buffering capacity against the influence of pollution. This factor can provide increased robustness against perturbations by climate change. “Of course, many other factors of pollution also affect climate and rainfall,” cautions the lead investigator, “but at least one important pathway seems to have a natural buffering capacity.”

The work was carried out in the central Amazon. Unmanned aerial vehicles (UAVs; drones) were flown over the forest. Atmospheric samples were collected onboard the UAV. The UAV can be described colloquially as a bird with an electronic nose. The work involved important international collaborations among researchers at Harvard University, Amazonas State University, University of California at Irvine, the University of North Carolina at Chapel Hill, and the Lawrence Berkeley National Laboratory. Read more details here. For more information, please contact Scot Martin (scot_martin@harvard.edu).

(left) Forest emissions of a precursor compound (highlighted in blue) and the important family of 2-methyltetrols (highlighted in green). Previously, only secondary production in the atmosphere by attack by hydroxy radical (OH) has been considered in models. The new observations show the discovery that these compounds are also emitted in large quantities by the forest.  (right) Unmanned aerial vehicles launched from a boat in the Amazon.