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How Do Drought Conditions Escalate Wildfires?

Darlene Rini, PE

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Jan 27, 2020

Australia is being ravaged by the worst bushfire in decades with more than 100 fires still burning. Since November 11 the fires have been responsible for more than 10 million burned hectares (approximately 25 million acres), at least 25 deaths and more than 2,000 homes destroyed and/or damaged. More than 1 billion impacted animals and the release of 100s of millions of tons of CO2 gases have made headlines across the world. The fires show no signs of stopping for the next few months.

How Drought Impacts Bushfire Activity

One factor that is driving the intensity, duration and historic magnitude of the Australian bushfires is drought. Rainfall was the lowest on record in areas of Queensland, New South Wales, South Australia, Western Australia and the Northern Territory between January and August 2019, according to the Bureau of Meteorology in Australia.

A wildfire requires fuel, oxygen and heat. The primary fuel in bushfires is provided by vegetative material—timber (such as eucalyptus trees), grasses and/or shrubs. When conditions remain dry for long periods, the moisture content of dead and even live vegetation will become dangerously low. This primes the fuels to be more easily ignitable, but also endangers live vegetation that are typically fire resistant, to be more vulnerable to ignition. These conditions can further exacerbate already fire-prone plants, such as the eucalyptus tree in Australia. The natural oils that give the eucalyptus trees their characteristic fragrance is highly volatile and flammable. This coupled with the natural large buildup of dry, leaf litter can create large intensity fires. While low relative humidity, high temperatures, dryness and strong winds set the stage for high fire dangers, drought conditions further amplify the intensity, scale and duration of the fires that may occur. They also exhaust the ability for trees and/or other vegetation to recover.

How Are California Fire Seasons Similar to Australia?

There have been many comparisons drawn between the ongoing fires in Australia and the 2017-2018 fire seasons in California. For starters, Australia has similar weather, terrain, vegetation and presence of communities pushing into fire prone wilderness to California, known as the wildland-urban interface. The arid conditions, high temperatures, seasonal high winds, topography and fire-prone fuels in California all contribute to the region’s propensity for wildfires, which also suffered from a five-year dry spell until 2017.

The main difference is that Australia has a stronger focus on self-reliance. They continually educate, train and prepare individuals and local communities to protect themselves, their family and their property from wildland fires. This includes hardening their homes, knowing what to expect in a wildfire, being prepared to evacuate and knowing when levels are too catastrophic to safely defend-in-place.

Recent Weather and Climate Trends

Over the last several decades, wildfire incidents and their intensity have increased, in part due to changing climate.

The increasing number of high fire danger days and duration of the fire season (which is now considered year-long in California), the number, scale and intensity of wildfires is predicted to increase and have far greater impacts beyond the local and/or regional values. In the 2019 IPCC Special Report on Climate Change and Land, it was revealed that human-induced climate change was playing an increasing role in wildfires.

Looking Ahead

Understanding how fires behave and developing science-based approaches to how we as individuals and communities can collectively mitigate and adapt in this ever-changing environment will be critical moving forward. Our team has deep experience in fire safety, structural fire resiliency and disaster risk management and can help you take action to reduce your wildfire and bushfire risk.