In a new discovery, scientists have identified the world's largest logjam, which is located in Canada's Nunavut in the Arctic and contains 3.4 million tonnes of carbon.
According to the study, throughout the Arctic, fallen trees make their way from forests to the ocean by way of rivers. Those logs can stack up as the river twists and turns, resulting in long-term carbon storage. Scientists have mapped the largest known woody deposit, covering 51 square kilometres (20 square miles) of the Mackenzie River Delta.
"To put that in perspective, that's about two and a half million car emissions for a year," said Alicia Sendrowski, a research engineer who led the study while at Colorado State University.
"That's a sizeable amount of carbon," she said, but it's not a carbon pool we know much about.
"We have great knowledge about carbon in other forms, like dissolved or particulate organic carbon, but not what we call 'large carbon' - large wood." That's starting to change.
The author of the study says scientists have known for decades that driftwood can really get around in the Arctic, but they are just beginning to quantify how much wood there is and how much of its carbon storage we risk losing to climate change.
The Arctic's cold, often dry, or icy conditions mean trees can be preserved for tens of thousands of years; a tree that fell a thousand years ago might look just as fresh as one that fell last winter, Sendrowski said.
"There's been a lot of work on fluxes of carbon from water and sediment, but we simply didn't pay attention to the wood until very recently. This is a very young field of research that is developing quite fast," said Virginia Ruiz-Villanueva, a fluvial geomorphologist at the University of Lausanne who was not involved in the study.
"And it's important to study this wood not only for the carbon cycle but in general for our understanding of how these natural fluvial systems work and how the rivers mobilise and distribute the wood."
