Wildfires Flashcards
The nature of wildfires
They are uncontrolled fires that destroy grassland, forests and other areas of vegetation.
They usually occur in rural areas but if they reach inhabited ones they will also destroy inhabited land and settlements.
Surface fires
The most common type of wildfire
Leaf litter or low-lying vegetation burns, resulting in an either low or high intensity fire.
They burn at around 900 degrees, however they cool quickly and are relatively easy to control.
Ground fires
When the ground itself burns (organic matter in the soil such as peat and tree roots).
It is a slow, smouldering fire with no flame and little smoke.
They burn at around 540 degrees for long periods of time.
Crown fires
Burn through the canopy, which is the top layer of foliage.
Loose bark allows fire to spread up the trunks of trees.
They can generate temperatures of around 1100 degrees.
They are intense, fast moving and difficult to maintain.
Vegetation type
Thick undergrowth or closely spaced trees allow fires to travel easily.
Some trees such as pine contain lots of oil so will burn easily.
Fuel characteristics
Fine, dry material (long grass, thin twigs) catch fire and burn easily.
Large amounts of fuel that form a continuous fire will burn for longer and spread quickly.
Climate and recent weather
Rainfall must be sufficient for vegetation to grow so there’s lots of fuel.
They usually require a significant dry season when rainfall is low for a significant time.
Strong winds provide oxygen to help the fire burn and spread.
When humidity is below 7% the risk is much higher, it tends to be the lowest in the early afternoon.
Fire behaviour
Different types of fire burn in different ways, creeping fire moves across the ground fairly slowly whereas running fire spreads rapidly.
Fire can throw out burning debris called firebrands that help the fire to spread.
Natural causes
Lightning can start fires if it occurs without much rain.
Volcanic eruptions can produce every hot lava which can start fires.
They can also start from sparks from rock falls.
Hot vs cold lightning
Cold Lightning has an intense electrical current but has a short duration.
Hot Lightning has a lower voltage but occurs for a longer period of time - it is particularly long last hot lightning that causes wildfires.
Human causes
90% of fires in the USA are started by people leaving campfires unattended, dropping cigarettes, lighting agricultural fires or arson.
Multiple causes
E.g. In south east Australia Feb 2009, fires were caused by lightning, a downed power line and arson.
Social impacts
People killed, injured or left homeless
Power lines destroyed, reservoirs damaged, meaning that people don’t have electricity or clean water.
Inhaling smoke can lead to long term breathing difficulties.
Political impacts
Governments can face criticism when fires have severe impacts.
Economic impacts
Businesses destroyed
Insurance increases
Costs to fight fires
Tourists are discouraged
Environmental impacts
Habitats destroyed, some species may not return to the area after the fire, changing the Eco system
Soils are damaged as fires remove organic matter
Smock causes pollution and water becomes contaminated with ash.
Australia wildfire key facts
Wildfires burned for a month in the state of Victoria.
The worst conditions occurred in forested areas.
The fires followed 10 years of drought, temperatures of over 40 degrees and strong winds.
There was a large amount of dry oil-rich material to fuel the fire.
Impacts - Australia social
173 people killed, 400 injured
Rise in stress and depression
2000 homes in 78 communities destroyed
Short term responses
Trying to put the fire out or diverting it from settlements
Evacuating people
Spraying water onto the roofs of houses to prevent embers from setting them alight.
Prevention
Public education about e risks of campfires
Fire beaters can be provided by authorities to put out small fires before they spread
Preparedness
Households may have emergency plans or supplies of food, water or medicine
Emergency shelters may also be made available
Adaptation
Using non-flammable building material
Drive ways and patios may act as a barrier
Sprinkler systems
Fire breaks such as gaps in trees around settlements stop fires spreading
Australia wildfire responses - evacuation
The Australian Bureau of Meteorolgy predicted how the fires would spread and told residents they could either evacuate or stay put.
Evacuation reduced deaths but people were put at risk by choosing to stay.
Australian wildfire - economic impacts
60 businesses destroyed
Cost of fire = $4 billion
Australian wildfire environmental impacts
4300km^2 of land burned, including national parks
Rare species such as the spotted tree frog were killed.
Australian wildfire - other responses
20,000 fire fighters and volunteers helped to put fires out and support victims.
$400 billion was donated to rebuild homes however fire-resistant material increased the cost so not everyone could afford to finish building
Australian wildfire- long term responses
Fire shelters, warning systems and evacuation strategies are recommended as long term responses.
