Wildfires

Question 1

What are wildfires?

Answer 1

uncontrolled fires that occur in natural areas such as forests and grasslands

Question 2

What are the 3 types of wildfire?

Answer 2

• Ground fires - burn beneath the ground surface with tree roots and peat layers burning. They are smouldering, slow-moving fires that can burn for days and weeks with no visible flame and little smoke
• Surface fires - burn through low-lying vegetation such as grass, bushes and small trees. They are the most common and can move quickly
• Crown fires - burn through the canopy layer which is the top layer of vegetation. They are usually the most dangerous and destructive type of wildfire because they move quickly and often produce intense heat and flames
• all 3 fires can be present at once which makes them more difficult to manage and predict

Question 3

Spatial distribution of wildfires

Answer 3

Wildfires occur all over the world (except for Antarctica)

Wildfires are most common in the tropics and subtropics

Countries that experience the highest number of wildfires include Brazil, Indonesia and Australia

They are also common in large, forested areas of dense vegetation
e.g. Russia, Canada and USA all experience frequent wildfires

Question 4

How does vegetation/fuel type affect wildfires?

Answer 4

• Denser vegetation tends to lead to more intense fires that can spread quickly and burn for longer e.g. forest fires tend to be more dangerous and intense than grassland fires
• Some types of vegetation are more flammable than others e.g. eucalyptus contains highly flammable oils that burn very easily
• The amount of available fuel, such as trees, grass and dead plant materials affects the likelihood and severity of fires
• Fine, dry material such as grasses and twigs can catch fire and burn very easily

Question 5

How do climate and weather impact wildfires?

Answer 5

• Dry weather and droughts dry out vegetation and increase its flammability
• High temperatures and heatwaves increase rates of evaporation – this dries out vegetation even more and makes it more susceptible to ignition
• Strong winds can fan the flames of a fire and cause it to spread more quickly. Wind can also carry embers from a fire and start new fires elsewhere
• Lightning storms are a common cause of wildfire ignition
• Climate change is increasing the frequency and severity of wildfires in many regions around the world

Question 6

What are the causes of wildfires?

Answer 6

• Wildfires are caused by both natural and human factors, though most are caused by humans
• Natural causes include lightning strikes, volcanic eruptions and even the heat from the sun
• Human causes include campfires and barbecues getting out of control, cigarettes being discarded when they are still lit, and sparks from machinery or power lines
• up to 70% due to arson and 80% in America as a result of human cause

Question 7

How can people prepare for wildfires?

Answer 7

• Preparedness and adaptation include making people more aware of hazards and taking action to minimise risk
• Satellites and infrared sensors can be used to improve early detection and monitoring
• Warnings can be issued to allow time for evacuation and high-risk zones identified
• Evacuation plans can be prepared and emergency services trained to improve response
• Education campaigns can inform people how to create defensible spaces around their homes

Question 8

How can wildfires be mitigated against?

Answer 8

• Firefighters often use helicopters and airplanes to drop water and fire retardants onto fires to reduce the intensity of the fire and slow its spread
• Backburning - firefighters light small fires ahead of a larger wildfire to reduce the amount of fuel available to help slow or stop the spread of the fire
• Public awareness campaigns and rules on use of campfires and barbecues can reduce the chances of a wildfire starting
• Firebreaks can be used to reduce the chances of wildfires spreading by creating deliberate gaps in forested areas
• Controlled burning can reduce the amount of fuel available
• Building codes can be implemented to ensure fire-resistant materials are used in construction and sprinkler systems are installed

Question 9

What strategies can be used to reduce wildfires?

Answer 9

• thin tree cover, trim branches and remove debris
• trim branches to 10ft above ground
• clean gutters and drains to remove litter
• reduce density of grass and surrounding forest close to the home

Question 10

How do slopes influence wildfires?

Answer 10

• fires on a 20 degree slope advance at 4x the rate of fires on level ground
• vegetation is preheated as hot air rises, causing the advance of the fire front vertically

Question 11

Issues with managing wildfires

Answer 11

• scale - cover extensive areas and may be multiple sources for fires
• accessibility - difficult to access upland areas due to lack of transport
• uncontrollable - spreads very quickly in strong winds, dry material and steep slopes
• whole population needs to be evacuated due to unpredictability
• prolonged impacts on health

Question 12

How is climate change changing wildfires?

Answer 12

• affects natural cycles
• heatwaves are increasing - used to be on average once every 20 years in Australia, now every 6 months+

Question 13

Why were Victoria particularly vulnerable?

Answer 13

• covered by eucalyptus forest which is oil-rich foilage - will quickly burn
• periodic droughts during summer where temps exceed 40 degrees - produces tinder-dry vegetation
• high winds - produces drier conditions and quicker fire spread
• depopulation in rural areas so lack of services

Question 14

Why were the impacts so severe?

Answer 14

• 10 year drought led to the build up of leaf litter from trees - rich in highly flammable oils so little management to guard against fires
• steep slopes and valleys that channel hot air
• the wind gusts of more than 100 km per hour changed direction late in the day, causing unpredictable fire paths.

Question 15

What were the impacts of the fires?

Answer 15

• 173 deaths
• 3500 properties destroyed and 7000 displaced
• over 1 million acres land burnt
• $4.4 billion total cost estimated with $1.2 billion insurance claims - huge impacts on local economy

Question 16

What were the immediate responses and how effective were they?

Answer 16

• Many countries offered to send out all types of assistance in response to the fire, including humanitarian, fire aid, and rebuilding support - more than $400 million was donated.
• Over 4000 firefighters from the Victorian Country Fire Authority along with firefighters from other states, New Zealand and the US were sent out to fight the fires.
• Australian Bureau of Meteorology predicted how the fires would spread and told residents that they could either evacuate or stay and defend their homes.
• Many witnesses criticized the lack of official information about the speed and direction of the fires, leading to confusion and distress among those trying to evacuate
• Australian Red Cross Victorian Bushfire fund

Question 17

What were the long-term responses?

Answer 17

• new fire hazard system - BOM forecast an outlook for the fire danger index (FDI) and advise residents to leave on high risk days
• government urged to ban building houses in high-risk areas - however went against this and came under criticism for allowing the rebuilding of Marysville where 90% property was destroyed

Question 18

Which areas were worst affected?

Answer 18

• Kinglake and Marysville - 90% property destroyed and over 100 deaths