Smouldering

• Others were rescued by the U.S. Coast Guard after going into the ocean to escape the flames.
• Fires were still burning on Aug. 10, both in Maui’s tourist-filled west coast and farther inland, as well as on the Big Island of Hawaii.
• Dry grasses and strong winds, influenced by Hurricane Dora passing far to the south, heightened the fire risk.
• That number – people directly exposed to wildfires – more than doubled from 2000 to 2019, my team’s recent research shows.
• Instead, three-quarters of this trend was driven by intense fires growing out of control and encroaching on existing communities.

What climate change has to do with wildfires

• Recent research on California’s fires found that almost all of the increase in that state’s burned area in recent decades was due to anthropogenic climate change – meaning climate change caused by human activities.
• Our new research looked beyond just the area burned and asked: Where were people exposed to wildfires, and why?

Where wildfire exposure was highest

• If you picture wildfire photos taken from a plane, fires generally burn in patches rather than as a wall of flame.
• Three-quarters of the 125% increase in exposure was due to fires increasingly encroaching on existing communities.
• In California, the state with the most people exposed to fires, several wildfire catastrophes hit communities that had existed long before 2000.

What communities can do to lower the risk

• How much these fires grow and how intense they become depends largely on warming trends.
• But communities will also have to adapt to more wildfires.
• Developing community-level wildfire response plans, reducing human ignitions of wildfires and improving zoning and building codes can help prevent fires from becoming destructive.

• Apocalyptic orange skies and air pollution levels that force people indoors only tell part of the story, though.
• As global temperatures rise, fires are also spreading farther north and into the Arctic.
• These underground fires are known as “zombie fires,” and there are a number of reasons to worry about the trend.
• Recent research finds that Arctic soil fires can smolder through the winter and reignite during early spring when temperatures rise, hence the nickname “zombie fires.”

The Arctic is increasingly flammable

• However, the severity, frequency and types of wildfires in northern and Arctic regions have changed in recent decades.
• One major culprit is the rising temperature: The Arctic is warming nearly four times faster than the rest of the world, a phenomenon known as Arctic amplification.
• As the Arctic warms and fires move farther northward, peat soils rich in dead plant material burn at an accelerated rate.
• Northern ecosystems store twice as much carbon in their peat and permafrost as the atmosphere, and both are increasingly vulnerable to fire.

What is a zombie fire?

• Ground fires, on the other hand, do not flame but burn more slowly and have the tendency to spread deep into the ground and spread laterally.
• During the 2019-2020 fire season in Siberia, zombie fires were blamed for rekindling fires the following year.
• They were ignited by slash-and-burn activities to plant palm plantations and amplified by drought conditions during a severe El Niño event.

Some hope and caution from past lessons

• My work and that of many colleagues, however, focus on the combustion of above-ground biomass.
• In the meantime, the continuing waves of wildfire haze in Canada and the U.S. are a reminder of the impact of these fires.
• Best practices for safely fighting zombie fires are also needed, along with better public education about the health risks of wildfire smoke.

• This article is part of La Conversation Canada’s series The boreal forest: A thousand secrets, a thousand dangers La Conversation Canada invites you to take a virtual walk in the heart of the boreal forest.
• It also avoids stoking the pervasive negative perceptions regarding wildfire, which in the boreal is an essential agent of forest renewal and health.
• As a team of scientists who have dedicated our careers to understanding changing boreal fire regimes, we decided to find out for ourselves.

Unusual fire behaviour

• Fire behaviour refers to the way a fire burns.
• This seemingly unusual fire behaviour was previously of limited concern as overwintering fires are hard to detect and, we think, were relatively infrequent.

Remote fire study

• Last summer, our team visited sites in the southern Northwest Territories that had ignited in 2014, experienced overwintering fire, and reignited in 2015.
• These were paired with neighbouring sites from the same 2014 fire that had experienced only a single season fire.
• All potential sites were incredibly remote and could only be accessed by helicopter — our team was able to use one that was on standby for fire duty as it was a relatively quiet fire season.

Carbon emissions

• The most socially relevant concern relates to carbon emissions and potential feedbacks to climate warming.
• Boreal peatlands are thought to store as much as 30 per cent of the Earth’s terrestrial carbon stocks.
• As such, threats to these regions have the potential to compound already rapid increases in atmospheric carbon dioxide concentrations that underlie global warming.

Failure to renew

• We expect that zombie fires will lead more commonly to regeneration failure — conversion of forest to non-forest — for three main reasons.
• Changes in forest type or failure for forests to recover affects wildlife habitat availability among other impacts, an issue of increasing concern, particularly in the context of declining caribou populations across North America.

Remote sensing advances

• However, advances in space-borne remote sensing have allowed the detection of early spring reignitions, which when combined with information on fire perimeters from the previous year, support accurate detection and mapping of overwintering fires that reignite.
• It will also lead to important insights into carbon losses from this fascinating — although poorly understood — fire behaviour.
• These research grants and contracts support fundamental research on the response of northern high latitude ecosystems to permafrost thaw and wildfire.

• Findings suggests that multiple organ rejection events may actually be one, longer, smoldering rejection event.
• "Having a precision-medicine approach to treating organ rejection has the potential to markedly reduce the threat rejection poses to transplanted organs," Woodle says.
• However, once a kidney transplant recipient experiences acute rejection, many go on to lose their transplant and return to dialysis within 1-3 years.
• "Thanks to insights like these, we may be able to substantially reduce loss of transplanted organs to rejection, thereby freeing up donated organs for new transplant recipients."