Record fire years sow seeds of severe future fires, scientists say
A wildfire burns on a mountain near Ashcroft, B.C., late Friday July 7, 2017. More than 3,000 residents have been evacuated from their homes in central British Columbia. A provincial state of emergency was declared after 56 new wildfires started Friday. (THE CANADIAN PRESS/Darryl Dyck)
The increasing frequency of record-breaking fire seasons playing out in B.C. is sowing the seeds for severe fire seasons to come, according to the co-author of a recent study.
Each successive fire and the carbon released leads to more drought, crippling the ability of forests to absorb and sequester carbon, said David Galvez, a former researcher at the University of B.C. and University of Alberta.
This year's forest inferno is being mirrored on every continent, according to the new study examining the mechanics of tree death.
"What we are seeing in B.C. is what you expect in the modelling," said Galvez, who now works for Abattis Bioceuticals. "Four of the worst fire years in the past 70 years have come in the past seven years and that's amazing."
According to figures from the Ministry of Lands, Forests and Natural Resource Operations, the years 2010, 2013, 2014 and 2015 are in the top 10 for hectares burned since 1950. This year more than one million hectares of B.C. forest have burned to date, eclipsing a 58-year record.
Recent modelling by the Canadian Forest Service predicts climate change is driving up the number of fires and leading to more "fire-conducive weather" in B.C. The study — Future burn probability in south-central British Columbia — was published last year by the International Journal of Wildland Fire.
The new meta-analysis — using data from 62 scientists around the world — found that trees in droughty conditions shut pores that let in carbon dioxide in order to conserve moisture and form air bubbles that block water transport within the tree, leading to lethal hydraulic failure and carbon starvation.
The study was published in Nature Ecology and Evolution.
Knowing how and under what conditions trees die in drought is essential to making predictions about how forest die-offs impact climate change, according to Galvez.
Forests play a huge role in absorbing and sequestering atmospheric carbon, but that function is being crippled by more frequent drought.
"The global effects of climate change are leading to extensive tree mortality," said Galvez. "We can see that drought will become more frequent and longer, which will lead to forest death and more fires, releasing even more carbon. The temperature goes up and everything starts again."
As forests adapt and change in response to new conditions their ability to sequester carbon changes, too.
"The conifer forests that we have in the north sequester carbon much longer than in more temperate forest," he said. "Tropical forests absorb carbon more quickly than conifer forest, but northern forests are much better at retaining carbon."
Is there more to this story? We'd like to hear from you about this or any other stories you think we should know about. Email email@example.com