Large wildfires similar to those seen in 2018 could now occur in any year, regardless of how wet the previous winter was, according to a new study published in the Proceedings of the National Academy of Sciences.
The study concluded that increased temperatures due to climate change and more effective efforts to contain fires have resulted in a build-up of dry wood and vegetation.
Up until 1904, the frequency and severity of wildfires was directly correlated with the amount of rainfall California experienced over the winter period, the paper found.
However, from this point onwards the connection weakened, coinciding with the introduction of a fire suppression policy on U.S federal lands, before completely disappearing after 1977.
Eduardo Zorita, a co-writer of the study, spoke to BBC News about what this means for wildfire risks going forward.
“Humans have a strong influence on fire events in several ways: directly, through fire suppression… but another indirect effect is that if human societies suppress fires, more fuel is available for later,” Zorita explained.
“Fire is a natural phenomenon that’s very important for forest dynamics on longer timescales: for the way that forests renew themselves and grow and incorporate new species… human societies interrupt these forest and fire dynamics,” he continued.
The resulting build-up of vegetation has now been exacerbated by rising temperatures due to climate change, meaning there is potential for large wildfire outbreaks every year, regardless of winter conditions.
“It may happen that for certain periods, the frequency of fires is suppressed by humans, but when a fire occurs, its intensity may be bigger than it would have been without human intervention,” Zorita continued.
For perspective, Aon noted that only seven individual wildfires had surpassed insured losses of $1 billion by the end of 2016, whereas the total has now risen to 13.