lecture 20: forest fires

Question 1

wildfire

Answer 1

worldwide phenomenon that appears in the rock record as charcoal quickly after land plants evolved in the ordovician period
- often depicted as destructure, natural process and essential to healthy forests
influences carbon cycle, distribution

Question 2

wildfires amount in canada

Answer 2

about 10% of worlds fires

- common in all canadian forests and shrub lands/grass lands

Question 3

boreal forests

Answer 3

cover 60% of canadas surface area, comprises mixed coniferous and deciduous trees

Question 4

how many wildfires in canada in the last century

Answer 4

consumed 2.5 million ha/years

2% of largest fires account for 97% of burning

Question 5

fire triangle

Answer 5

carbon hydrogen bonds in plant material are broken generaitng CO2, water vapour H20, and heat
- oxygen, heat, fuel

Question 6

ignition

Answer 6

can be human or natural (lightning = majority of total area burned)
humans through discarded cigarettes, campfires, powerlines and vehicles 50% of wildfires in CAN 80 in US

Question 7

3 phases of combustion

Answer 7

first phase: water expelled from plants and ground heated by nerby flames and heat
middle phase: greatest energy release of fire when flames are present
late phase: slower combustion rate and blue flame
glowing emits smoke but no flame and is rarely self sustained

Question 8

classes of forest fires

Answer 8

1. ground fires- occur on ground below leaves
2. surface fires- occur on forest surface up to 1m high
3. crown fires- tops of trees
   - common for 2/3 types to occur at same time

Question 9

ladder fuels

Answer 9

tall grasses and small shrubs that enables small ground fires to spread upward into tall trees and engulf the tree crowns, turning a small fire into a major one

Question 10

factors that conttrol likelihood of wildfire starting and spreading

Answer 10

climate and weather- temp, wind speed, humidity, lightning, soil moisture, rain
insects- pine beetle can destroy forests and leave dead combustible wood
chemical constituents of plants- high oil and easy cognition
topography- upslope of fire preferentially preheated by radiation of flames

Question 11

spread of fire

Answer 11

• can create its own weather –> moist air condenses to pyrocumulus clouds that produce rain
• rising air leaves behind low pressure at the surface drawing in downdrafts
• rising columns of hot unstable air cna be spun into danerous eddies called fire whirls

Question 12

fire suppression

Answer 12

need to remove at least 1 element

1. not enough heat generated to sustain process
   - adding water
2. oxygen supply limited
   - fire retardants
3. fuel is exhausted, removed or isolated
   - bulldozing or backburning

Question 13

backburning

Answer 13

starting small fires along a firebreak in front of a wildfire which redues the amount of fuel available to the wildfire once it reaches the burnt area

Question 14

lookout towers

Answer 14

used in Colorado to spot new fires

now we use air patrols and automated lightning detection systems

Question 15

what happened in north america in 19th century

Answer 15

wildfires have been aggresively surpressed since the late 19th century leading to a build up of forest fuels
- prescribed burning can be used to remove ladder fuels and create fuel breaks, carefully managed

Question 16

2016 fort mcmurray wildfire

Answer 16

first time a >60,000 residents were forced to evacuate due to a wildfire
- the fact that a city this large and also so remote owes everything to the prescence of vast oil sands
- cause is unkown but humans are suspected
final burn area 600,000ha

Question 17

what were the losses of fort mcmurray

Answer 17

2,400 buildings destroyed, 3.6 billion insured and 7 billion uninsured
canadas costliest disaster

Question 18

the great fire of 1919

Answer 18

swept through 2 million hectares of alberta and saskatchean, 4x the 2016 total
wildfires were not unprecedented

Question 19

how did 2016 fort mcmurray wildfire form

Answer 19

high pressure centre unusually far north brought hot southwesterley winds and record highs of 33 degrees

• happened after light winter snows had melted but before summer greening
• months ahead of typical summer wildfires

Question 20

el nino events

Answer 20

produce warm canadian winter so strong 2015-16 el nino added a hot spike to the long term

Question 21

damage of 2018 california campfire

Answer 21

death toll: 88, over 10,000 buildings destroyed
fires increasing in number and size and fire season gets longer
millions of acres burned per year in california