A recent study published in the journal Science reveals that a 3,775-year-old preserved log could significantly enhance strategies to combat climate change. The research highlights the log’s remarkable preservation, attributed to the low-permeability clay soil in which it was buried.

Conducted by a team led by Professor Ning Zeng from the University of Maryland’s Atmospheric and Oceanic Science department in the US, the analysis found that the log had retained over 95% of its carbon dioxide content, indicating that the conditions surrounding it were ideal for long-term preservation.

Understanding the environmental factors that contributed to the log’s longevity could play a crucial role in refining an emerging climate solution known as “wood vaulting”. This technique involves taking wood that is not commercially viable – such as trees damaged by disease, remnants of wildfires, or unused construction materials – and burying it to prevent decomposition.

This method aims to enhance carbon sequestration, as trees naturally absorb carbon dioxide throughout their lives. However, once they die and decay, that stored carbon is released back into the atmosphere, exacerbating global warming.

Key findings

Zeng noted the simplicity of the concept: “People tend to think, ‘Who doesn’t know how to dig a hole and bury some wood?’” However, he stressed the importance of appropriate conditions for preservation over long time scales. He referenced the numerous wooden coffins buried throughout history, many of which did not survive, underscoring the need for specific environmental factors to ensure longevity.

The discovery of the ancient log occurred during a wood vaulting pilot project in Quebec, Canada, in 2013. While digging a trench to bury fresh wood, Zeng and his team stumbled upon the well-preserved log approximately 6.5 feet underground.

“When the excavator pulled a log out of the ground and threw it over to us, the three ecologists I had invited immediately identified it as Eastern Red cedar,” Zeng recalled, expressing his amazement at the discovery.

While previous studies have examined preserved wood samples, they often neglected the surrounding soil conditions critical for long-term preservation. “There is a lot of geological and archaeological evidence of preserved wood from hundreds to millions of years ago, but the focus of those studies was not on engineering a wood vault to preserve that wood,” Zeng explained.

Primary factor

In 2021, Distinguished University Professor Liangbing Hu and Zeng conducted an in-depth analysis of the log’s microscopic structure, chemical composition, mechanical strength and density.

Their comparisons with freshly cut Eastern Red cedar logs indicated that the ancient sample had lost very little carbon dioxide, reinforcing its extraordinary preservation.

The clay soil’s low permeability was identified as the primary factor in the log’s condition. This type of soil limits oxygen access, inhibiting decomposition by fungi and insects, the usual decomposers found in soil. Given the widespread occurrence of clay soil, wood vaulting emerges as a viable and low-cost climate solution applicable in various regions.

Zeng emphasized that while this method could contribute to mitigating climate change, it should be implemented alongside other strategies to effectively address global warming, including reducing green-house gas emissions. As the team continues to optimize wood vaulting practices, Zeng is eager to apply their findings in real-world scenarios.

As researchers strive to develop innovative solutions to combat climate change, the study of this ancient log offers a promising avenue for enhancing carbon sequestration efforts and refining our approach to sustainability.

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