Are We Overestimating How Much Trees Will Help Fight Climate Change?

Bob Marra navigated his way to the back of a dusty barn in Hamden, Connecticut, belonging to the state’s Agricultural Experiment Station.  There, past piles of empty beehives, on a wall of metal shelves, were stacks of wooden disks — all that remains of 39 trees taken down in 2014 from Great Mountain Forest in the northwest corner of the state.

These cross-sections of tree trunks, known as stem disks — or more informally as cookies — are telling a potentially worrisome tale about the ability of forests to be critical hedges against accelerating climate change.  As anyone following the fires burning in the Amazon rainforest knows by now, trees play an important role in helping to offset global warming by storing carbon from atmospheric carbon dioxide — a major contributor to rising temperatures — in their wood, leaves, and roots.  The worldwide level of CO2 is currently averaging more than 400 parts per million — the highest amount by far in the last 800,000 years.

But Marra, a forest pathologist at the Experiment Station with a PhD in plant pathology from Cornell University, has documented from studying his fallen trees that internal decay has the capacity to significantly reduce the amount of carbon stored within.

His research, published in Environmental Research Letters late last year and funded by the National Science Foundation, focused on a technique to see inside trees — a kind of scan known as tomography (the “T” in CAT scan).  This particular tomography was developed for use by arborists to detect decay in urban and suburban trees, mainly for safety purposes.  Marra, however, may be the first to deploy it for measuring carbon content and loss associated with internal decay.  Where there is decay there is less carbon, he explains, and where there is a cavity, there is no carbon at all.

“What we’re suggesting is that internal decay in trees has just not been properly accounted for,” says Marra.

Read more at Are We Overestimating How Much Trees Will Help Fight Climate Change?