Across the Arctic, felled trees move from the forests to the ocean via rivers. These trunks can pile up as the river meanders, which allows for long-term carbon storage.
A new study published in the journal Geophysical Research Letters mapped the largest known tree deposit, covering 51 square kilometers of the Mackenzie River Delta in Nunavut. She also concluded that the trunks store around 3.4 million tonnes of carbon.
“To put it into perspective, that’s about two and a half million car emissions in one year,” said Alicia Sendrowski, research engineer and director of the study done in conjunction with the State University of Colorado.
She explains that this is a considerable amount of carbon, but admits that there is still little knowledge about what this carbon pool represents. “We are familiar with carbon in other forms, such as dissolved or particulate organic carbon, but not what we call ‘big carbon’, ie big wood. However, that is starting to change. »
The scientific community, however, has known for decades that wood can actually move through the Arctic by floating, but they are only just beginning to quantify how much wood and how much carbon storage is at risk of being lost to climate change.
“The cold, often dry or icy conditions of the Arctic allow trees to persist for tens of thousands of years; a tree that fell a thousand years ago can look just as fresh as a tree that fell last winter,” Ms. Sendrowski pointed out.
Three weeks of field research
To get a glimpse of ice jams, study researchers focused on the Mackenzie River, which has very high-resolution imagery and is known for heavy timber deposits. Its delta is the third largest in the world in terms of area and drains about 20% of Canada, the document notes.
The team surveyed around 13,000 square kilometers of delta in the largest attempt to map woody deposits to date. Researchers spent three weeks in the field measuring driftwood from the river, mapping ice jams and collecting wood samples for radiocarbon dating.
Experts have discovered that the repository, which includes more than 400,000 miniature wooden caches, stores around 3.4 million tonnes of carbon. The largest repository, which covers about 20 American football fields, alone stores 7,385 tons of carbon.
“But since there are still more trunks buried in the ground, submerged under water and hidden under vegetation by aerial imagery, the total amount of carbon stored in the delta wood could be about twice as large” , can we read in the study.
The Mackenzie River Delta is a carbon storage “hot spot” with incredibly carbon-rich soils, Sendrowski said. “As changes occur in the basin, such as logging or dam construction, and climate change alters rainfall patterns and warming, timber preservation will decline,” she concluded. .
With information from the American Geophysical Union