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Treehugger science

February 20th, 2010 · 1 Comment

Scientists at the Smithsonian Environmental Research Center have published a study, Evidence for a recent increase in forest growth, suggesting that climate change can quite literally be measured by treehuggers. Like the average American citizen, American trees look to have had increasingly bulging middles in recent decades. Having spent their careers quite literally hugging trees, SERC scientists Geoffrey Parker and Sean McMahon have written a study documenting

evidence that forests in the Eastern United States are growing faster than they have in the past 225 years. The study offers a rare look at how an ecosystem is responding to climate change.

For over 20 years, Parker has gone into a set of forests in the mid-Atlantic, tape measure in hand, and giving them a hug to measure their size. Parker’s own hugging has been extended with a robust group of volunteers conducting regular measurements of specified trees. (The boy scout to the right, while in a SERC forest, isn’t engaged in actual measurements for the study.) Some 250,000 hugs later, he has quite a database in hand. The results of analyzing hugs surprised these researchers. Based on the data from these 100,000s of hugs, Parker’s and McMahon’s analysis documents

that the forest is packing on weight at a much faster rate than expected. … on average, the forest is growing an additional 2 tons per acre annually. That is the equivalent of a tree with a diameter of 2 feet sprouting up over a year.

Now, there are many things that contribute to plant growth, from soil quality to rainfall to temperatures to CO2 concentrations. Parker and McMahon have concluded that the driver for the bulging middles of the studied groves is best explained through human impacts: the rising levels of CO2 (a nutrition); and the warmer temperatures and extended growing season due to global warming (driven, in no small part, due to the rising CO2 levels).

During the past 22 years CO2 levels at SERC have risen 12%, the mean temperature has increased by nearly three-tenths of a degree and the growing season has lengthened by 7.8 days. The trees now have more CO2 and an extra week to put on weight. Parker and McMahon suggest that a combination of these three factors has caused the forest’s accelerated biomass gain.

This was not some predetermined answer.

It was not enough to document the faster growth rate; Parker and McMahon wanted to know why it might be happening. “We made a list of reasons these forests could be growing faster and then ruled half of them out,” said Parker. The ones that remained included increased temperature, a longer growing season and increased levels of atmospheric CO2.

While the additional growth has some quite positive aspects, such as sequestering more carbon in the trees than would occur with ‘normal growth’, there are some aspects to consider:

  • Already, there are areas in the world where tree growth seems to be slowing — whether to climate disruption (such as disrupted water patterns), insects and disease enabled through warming (such as what is happening with North America’s spruce forests), and/or warming (some tropical areas are seeing growth slowing, perhaps due to temperatures simply being too warm.
  • Warmth, Co2, and growing seasons aren’t the only factors enabling growth. Could the tree growth be limited due to other factors (rain, nutrients)? And, there are simply limits to growth which the trees will reach (sooner).

As explained by Professor Kenneth Feeley, Florida International University

“The danger of that, of course, is that this can’t go on forever,” He meant that, even if there was enough carbon dioxide to support more fast growth, the trees would eventually run out of water or plant food. Their growth would slow down, and they would stop absorbing so much carbon.

From the Smithsonian Environmental Research Center’s press release:

Parker and McMahon don’t expect SERC’s forest to continue growing at this accelerated rate forever. Some day the growth rate will level off. When that happens, they wonder how that will affect CO2 levels. If trees are sponges that absorb CO2, what will happen to CO2 levels in the atmosphere when the trees become saturated? It’s a question for further exploration.


Forget that temperatures have gone up 0.3 degrees Centigrade and the growing season has lengthened by 7.8 days over the past 22 years since, after all, the DC’s region’s “snowmaggedon” clearly proved that global warming is false if we would only listen to inane gleeful commentary from too many rejecting scientific work.

Just another group of ‘treehuggers’ talking about Global Warming when we should evidently be listening to noted climatologists like the anti-science syndrome promoting Attorney General of the Commonwealth of Virginia, Ken Cuccinelli, who is intent on spending taxpayer funds on a frivolous lawsuit attacking science while Virginia’s Governor Bob McDonnell is proposing massive cuts to Virginia’s educations programs.

At the Washington Post, David A. Fahrenthold’s Climate change’s impact on forests being measured via expanding tree trunks provides a flavor of ‘tree-hugging’ humor:

That tree is a poplar. The ones next to it are un-poplar (say it aloud). That’s a beech tree. The one next to it?

A son-of-a-beech.

The Proceedings of the National Academy of Sciences article: Evidence for a recent increase in forest growth abstract:

Forests and their soils contain the majority of the earth’s terrestrial carbon stocks. Changes in patterns of tree growth can have a huge impact on atmospheric cycles, biogeochemical cycles, climate change, and biodiversity. Recent studies have shown increases in biomass across many forest types. This increase has been attributed to climate change. However, without knowing the disturbance history of a forest, growth could also be caused by normal recovery from unknown disturbances. Using a unique dataset of tree biomass collected over the past 22 years from 55 temperate forest plots with known land-use histories and stand ages ranging from 5 to 250 years, we found that recent biomass accumulation greatly exceeded the expected growth caused by natural recovery. We have also collected over 100 years of local weather measurements and 17 years of on-site atmospheric CO2 measurements that show consistent increases in line with globally observed climate-change patterns. Combined, these observations show that changes in temperature and CO2 that have been observed worldwide can fundamentally alter the rate of critical natural processes, which is predicted by biogeochemical models. Identifying this rate change is important to research on the current state of carbon stocks and the fluxes that influence how carbon moves between storage and the atmosphere. These results signal a pressing need to better understand the changes in growth rates in forest systems, which influence current and future states of the atmosphere and biosphere.

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