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Science
| 07/20/17

BC wildfires caused in part by and contributing to climate change

TCE

As widespread wildfires across central British Columbia approach a raft of records, climate and forestry researchers say that climate change is a contributing factor to the crisis while the fires are also contributing to global warming.

The province has declared a state of emergency and, at the time of writing, more than 45,000 people had been evacuated from their homes, according to Emergency Management BC. This number is not far off the 2003 all-time record of 50,000 displaced from their homes as a result of a fire near Kelowna.

As of 19 July, some 354,000 hectares in BC have been burnt by wildfires so far in 2017, according to the BC Wildfire Service, a sharp jump up from the roughly 100,000 hectares burnt in 2016, a year somewhat below normal. And 2017 has the potential for many more weeks of burning.

As the planet warms, the province is in general experiencing warmer, drier summers, although conditions vary significantly from region to region. Global warming also means more water vapour in the air, and thus an increase in precipitation, which, along with greater carbon dioxide concentration in the atmosphere, can in parts result in a boost in plant growth.

So how can it be both wetter and drier at the same time?

Climate change is altering the seasonality of rainfall as well. Much of the increase in precipitation is occurring in winter and spring, not the summer, and given the warmer temperatures, it is falling as rain, rather than snow. This is driving earlier, stronger glacier run-off and snow-melt. Forest conditions dry out earlier, leading to earlier and longer wildfire seasons in some places.

According to Werner Kurz, a forestry researcher with Natural Resources Canada and the head of PICS’ flagship Forest Carbon Management Project, fresh data shows that wildfires this year started early and the area burnt is already well above average. This has significant import for greenhouse gas (GHG) emissions.

He says that in 2014 and 2015, the latest years for which we have GHG emissions figures, the average release due to wildfires over those two years was 58 million tonnes of carbon dioxide equivalent (CO2eq – carbon dioxide, nitrous oxide and methane).

This is ten times the average annual release from 1990-1999, he says.

In 2014, the stronger of the two years, 67 million tonnes of CO2eq were released, more than all other sectors—transport, buildings, industry, waste and agriculture—combined.

Kurz is reluctant to call this the ‘new normal’ just yet. Even a 20-year period of above-average wildfires is a very short period from a forest records perspective. But the trend is definitely toward increased intensity and length of wildfire season, albeit for some regions and not all of BC.

He does offer one caveat to all this. Initial regrowth after fires tends to be dominated by broad-leaf tree species such as alder, aspen and birch, which due to their leaves’ greater moisture content compared to the needles of conifers, burn much less. This could work as a natural firebreak.

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GHG emissions from BC wildfires in 2014 were more than from all other sectors put together

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