Deep in the Canadian Arctic, you can find a 51-square-kilometer (20-square-mile) pileup of fallen trees and ancient wood. Scientists have recently mapped this woody pile-up – the largest “logjam” in the world – and believe it’s likely to be having a massively underappreciated impact on the planet’s carbon cycle.
The pile-up is located in the Mackenzie River Delta in Nunavut, the largest and most northern territory of Canada. In a new study, scientists at Colorado State University used high-resolution satellite imagery and deep learning artificial intelligence (AI) to map this vast wood deposit.
Altogether, it’s almost as large as Manhattan, but it can be broken down into 400,000 miniature caches of wood, the largest of which covers around 20 American football fields.
Trees act as a carbon sink for the planet, sucking up carbon dioxide from the atmosphere and storing it in their wood. As such, they have a significant impact on the levels of greenhouse gases in the atmosphere and climate change. However, the researchers say logjams like this are often ignored when it comes to their impact on the wider environment.
“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. 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, how the rivers mobilize and distribute the wood,” Virginia Ruiz-Villanueva, a fluvial geomorphologist at the University of Lausanne who was not involved in the study, said in a statement.
This latest estimate calculated that the logs in the Mackenzie River Delta store about 3.4 million tons of carbon – which is a significant quantity, even on a global scale.
“To put that in perspective, that’s about two and a half million car emissions for a year,” explained Alicia Sendrowski, a research engineer who led the study while at Colorado State University.
“That’s a sizeable amount of carbon,” she added.
Since this survey was only able to measure the surface of the logjam, it wasn't able to calculate the wood that's hidden beneath, meaning the true scale of the driftwood carbon store might be even higher.
Wood has piled up here for a few different reasons. Firstly, drift in the Arctic has a habit of being transported across vast areas thanks to its expansive boreal forests and network of high-latitude rivers. Secondly, the Mackenzie Delta is huge, allowing heaps of felled wood to congregate.
Lastly, the Arctic’s cold and often dry conditions mean the trees can remain in near-perfect condition for tens of thousands of years. The researchers noted that some of the trees in the logjam look like they fell last winter, but they’re actually decades or centuries old.
Carbon dating has revealed that many of the trees likely started growing in the 20th century, while some have been dated as far as 1,300 years old. However, there’s a decent chance the logjam is holding trees that fell thousands upon thousands of years ago.
The study is published in Geophysical Research Letters.