14. Formation and Effects of Wildfires Flashcards
1
Q
Types of fires
A
- Crown fire
- Surface fire
- Ground fire
2
Q
Crown fire
A
Spreads across tree canopies
3
Q
Surface fire
A
Burns across surface vegetation
4
Q
Ground fire
A
Burns beneath the ground in layers of peat
5
Q
The ladder effect
A
Process where fires from the forest floor spread to the tree canopy
6
Q
Where are wildfires most common?
A
- Areas of the world prone to wildfires are those with a combination of dry vegetation and lightning strikes.
- Fires and natural ecosystems are closely linked e.g. in Savannah grasslands and mediterranean climates
- Fire can clear vegetation, aid seed germination and rid an area of insects and parasites
- Some plant species are pyrophytic and can withstand fire through fire resistant bark
- In Australia, plants like the banksia need fire for their woody fruit to open and thus regenerate - Regions that experience dry seasons along with semi-arid areas are at risk of drought are also prone e.g. Australia, Southern Europe, California
7
Q
What conditions favour wildfires?
A
- Vegetation type
- Climate and hot weather conditions
- Normal year
- El Niño
- La Niña
8
Q
Vegetation type
A
- Type and amount of of fuel influences intensity and rate of spread.
- Moisture content
- Eucalyptus is fire promoting
9
Q
Climate and hot weather conditions
A
- Heatwaves, drought and cyclical climatic events can create favourable conditions
- Most wildfires occur during or after prolonged dry periods
- Strong, dry winds blowing from continental interiors or deserts exacerbate the drying process.
- Wind strength determines rate of spread
10
Q
A normal year
A
- High air pressure in South America
- Low air pressure in Australia
- Trade winds move warm surface water towards the western Pacific
- Cold water wells up along the west coast of South America
11
Q
El Niño year
A
- High air pressure in Australia
- Low air pressure in South America
- Air pressure over the west coast of South America becomes unusually low and that over northern Australia particularly high
- The normal east to west trade winds over the Pacific are disrupted and warm water ‘sloshes’ eastwards
- Upwelling of cold water on the South American coast is suppressed
12
Q
La Niña year
A
- High pressure air in South America
- Low air pressure in Australia
- Air pressure is unusually high over the west coast of South America and low over northern Australia.
- The easterly trade winds are more intense than normal
- More warm water is pushed to the west of the Pacific Ocean.
13
Q
Causes of wildfires
A
- Can be ignited by natural causes or can involve human factors
- E.g. discarded cigarettes and poorly controlled campfires
- Heat transfer processes preheat vegetation ahead of flames
- Lightning strikes
- Burning fragments of vegetation can be carried ahead of fire front by convection currents + strong winds
14
Q
Global impacts of wildfires
A
- Destruction of businesses
- Increased carbon emissions impact on greenhouse effect and climate change
15
Q
National impacts of wildfires
A
- Displacement- people temporarily forced to live elsewhere
- Governments formulate new strategies and legislation to manage future wildfires
16
Q
Local/ regional impact of wildfires
A
- Loss of life and injuries
- Pressure on local authorities
- Damage to buildings/ structures
