Climate change tree stressors feeding US wildfires
Published:15 September 2020
Townsville-based CQUniversity researcher and head of course for environmental science, Dr Nathan Brooks-English
Climate change-amplified droughts are slowly suffocating North America’s iconic pine forests, creating the perfect conditions for the deadly wildfires currently devastating the United States’ west coast.
Townsville-based CQUniversity head of course for environmental science, Dr Nathan Brooks-English, originally hails from Portland in the US Pacific North West, and has focused his research on understanding the carbon budgets of forests around the world.
“The frightening scenes we are witnessing in the US are all too familiar to Australians, particularly after the devastating bushfires we endured last summer,” Dr English said.
“And while there are numerous factors at play, one thing we know for certain is that dead pine forests are more likely to burn hot and lead to disastrous outcomes for the environment and the communities living in those areas.”
In a research paper published this week in the journal New Phytologist, Dr English and collaborators from universities and research agencies in the US, China, and Switzerland, have examined the underlying causes of the increasing rates of conifer tree mortality in North America.
They found that ‘carbon starvation’ – the depletion of carbon stores in a tree as a result of long-term drought conditions that lead to stomatal closure – made trees more vulnerable to death.
The team examined long-term data of carbon stored at eight different North American forests, for both dying and surviving trees.
They found that compared to the surviving trees, lower growth of dying trees was detected at least one decade before mortality at seven of the eight sites.
“Scientists around the world have shown that rising temperatures, extreme drought and groundwater deficits are increasing as a result of climate change and higher-levels of greenhouse gases,” Dr English said.
“What we know now is that these drought conditions have already had long-term impacts on the vulnerability of North American pine forests and their ability to survive in a changing climate.
“The end result, tragically, is that we have more dead and dying trees now fueling hotter and more devastating fires.”
Dr English said further research was required to understand the many bio-physical factors contributing to the final cause of death of these slow-dying conifer forests, but recommended that these underlying causes be factored into future forest health assessments and tree management systems.