Wildfires: Understanding a growing risk

From 2001 to 2023, 138 million hectares of tree cover were lost due to wildfire – an area the size of South Africa. Not only are trees and forests destroyed by these wildfires, but homes, livelihoods and whole communities, too. Even people not directly impacted may be affected by inhaling wildfire smoke, causing respiratory and cardiovascular issues.

There is also a high economic cost. In California, for instance, between 2017 and 2021, average annual wildfire losses totaled over USD 117.4 billion, which comprises direct and indirect losses including labor market disruptions, property damage, response and clean-up costs, and loss of life. Indonesia’s 2019 wildfires, which burned 3.1 million hectares (an area the size of Belgium), inflicted USD 5.2 billion in losses – equivalent to 0.5 percent of Indonesia’s GDP.

Wildfires can also leave downhill and downstream communities vulnerable to flooding and mudslides due to the destruction of trees and grasslands that would have absorbed rainfall.

Worryingly, the IPCC says the intensity and frequency of wildfires is only likely to increase due to global warming. As temperatures rise, more moisture will be drawn out of soil and vegetation to create tinder-dry conditions that provide fuel for fires, which can spread at an incredible speed, particularly if winds are strong.

Canada is already feeling the wrath of wildfires. In 2023, it experienced its worst wildfire season on record. Over the course of the season – that started early and ended late – wildfires burned an area covering an estimated 18.4 million hectares. That’s more than seven times higher than the average 2.5 million hectares that burn in Canada each year. Research undertaken by World Weather Attribution found that climate change more than doubled the likelihood of “fire weather” conditions in eastern Canada between May and June 2023 that helped fires to spread.

According to the UN Environment Programme (UNEP), the situation is likely to deteriorate. UNEP says that a combination of climate change and land-use change will increase the number of wildfires by 30 percent by the end of 2050 and by 50 percent by the end of the century. Even regions like the Arctic, previously unaffected by wildfires, could come under regular threat.

“We have seen wildfires increase in intensity and destructiveness in recent years,” says Nicolette Botha, Head of Climate Resilience and Sustainability Asia Pacific at Zurich Resilience Solutions. “Wildfire seasons are starting earlier and finishing later in the year across the globe and are impacting areas that were once seen as risk-free. In the face of this growing risk, businesses, communities, and individuals need to better understand wildfires and learn how to prepare, respond and recover from them.”

What causes wildfires?

There are three components required for a wildfire:

• A heat source: This could be the sun, a bolt of lightning or a lit match.
• Fuel: This could be any flammable material, including dry grass, leaves and trees.
• Oxygen: Fire feeds off oxygen, which increases in high winds that also help spread the fire.

Wildfires happen naturally in many parts of the world and are an integral part of ecosystems. Yet human activity is estimated to be responsible for nearly 85 percent of wildland fires in the U.S., for instance. These human-caused fires may be triggered by unattended campfires, discarded cigarettes, fallen powerlines and even intentional acts of arson. Prescribed fires (or controlled burns), which are set intentionally for positive reasons – to reduce the risk of extreme wildfires, for instance – can also become uncontrollable.

Types of wildfires

There are three main categories of wildfire:

• Surface fires burn in dead or dry vegetation, such as parched grass or fallen leaves or branches at ground surface level. These fires can burn fiercely and spread fast with long flames.
• Crown fires occur less frequently, during hot and dry summers, but are the most dangerous. Crown fires burn through the top layer of foliage on a tree or tall shrubs. They are the most intense type of wildfire and the most difficult to control.
• Ground fires ignite within peat or soil, feeding off organic material like plant roots and smoldering until they grow into a surface or crown fire. Smoldering peat fires are hard to extinguish and can rekindle frequently.

Wildfires can also be defined by regions and their associated climates. “Wildfire” has widely replaced “forest fire” as common terminology for wildland fires, but “forest fire” can be useful in distinguishing fires in woodlands from those in grasslands or shrublands. The latter fires are often called “brush fires,” not to be confused with “bushfire,” the common general term for woodland and grassland wildfires in Australia.

“As with all extreme weather events, wildfires require both long-term and immediate planning,” adds Botha. “It is also vital that you safely respond and recover from any wildfire event.”

The following articles provide advice to help businesses prepare, respond and recover from wildfires: