Emissions of natural gas, also known as methane, are of great interest, inasmuch as methane in the atmosphere acts like carbon dioxide to warm our planet. Methane is one of several “greenhouse gases” that are effective in absorbing infra-red or heat radiation trying to leave the Earth. Indeed, molecule-for-molecule methane is about 25X more effective than carbon dioxide in heating the atmosphere.

The concentration of methane in the atmosphere is increasing, mostly likely due to human activities. Accusatory fingers point to leakage from the oil and gas industry, but emissions from the burps of cows and from rice paddies are also responsible. After all, the cultivation of rice and diets rich in meats have also increased markedly during the past 100 years, along with our consumption of petroleum.

Those responsible for methane leakage are quick to suggest that methane is emitted from other sources too. Several studies have reported methane emissions from trees. Some of these trees are hollow and harbor anaerobic bacteria inside, which release methane. Other trees, living in flooded soils, conduct methane upward inside their trunk and emit methane from the surface of the leaves and bark. These methane emissions were first noted about 40 years ago.

Methane emissions from trees are certainly not responsible for the rising methane concentrations in Earth’s atmosphere. Trees were emitting methane well before the concentration in Earth’s atmosphere began to rise about a century ago. At that time, the reactions that destroy methane in the atmosphere were adequate to keep up with methane emissions, and the concentration in the atmosphere was fairly stable at about 650 parts per billion for 1000s of years. (Now it is roughly three times that amount).

Emissions of methane from trees are part of the total budget of methane, which includes natural and human-derived sources. However, we should not let this source of methane divert our attention from emissions from human activities that dominant the current accumulation of methane in the atmosphere.

Plugging the leaks of methane from gas wells and the gas pipelines that crisscross our country is probably the easiest, most effective, and straightforward way to curtail the rise of methane in the atmosphere and mitigate the potential for undesirable climate change. Methane escapes from pipelines and natural gas wells, especially those employing hydraulic-fracture methods to extract the gas. The companies that supply natural gas to our homes will benefit by reducing the waste of the product they want to sell.

Let’s not let a few farts from trees distract us from the real job that lies before us.

References

Covey, K.R., S.A. Wood, R.J. Warren, X. Lee and M.A. Bradford. 2012. Elevated methane concentrations in trees of an upland forest. 2012. Geophysical Research Letters 39: doi: 10.1029/2012GL052361

Mitchell, L., E. Brook, J.E. Lee, C. Buizert and T. Sowers. 2013. Constraints on the late Holocene anthropogenic contribution to the atmospheric methane budget. Science 342: 964-966.

Pangala, S.R., E.r.C. Hornibrook, D.J. Gowing and V. Gauci. 2015. The contribution of trees to ecosystem methane emissions in a temperate forested wetland. Global Change Biology 21: 2642-2654.

Pitz. S. and J.P. Megonigal. 2015. Temperate forest methane sink diminished by tree emissions. Manuscript in review.

Sapart, C.J., G. Monteil, M. Prokopiou, R.S. W. van de Wal., J.O. Kaplan, P. Sperlich K.M. Krumhardt, C. van de Veen, S. Houweling, M.C. Krol, T. Bluner, T. Sowers, P. Mrtinerie, F. Witrant, D.D. Jensen and T. Rockmann. 2012. Natural and anthropogenic variations in methane sources during the past two millennia. Nature 490: 85-88.

Zeikus, J. and J.C. Ward. 1974. Methane formation in living trees: a microbial origin. Science 184: 1181-1183.