biophysical hazards. reading smith ch 10 biophysical hazards “dustbin” category for various...
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Biophysical Hazards
• “dustbin” category for various assorted hazards– disease– extremes of
temperature– wildfire
Disease organisms
• Microbes: Bacteria, viruses, prions
• Parasites
• can affect people directly
• can affect crops
Infectious Disease
• Interaction between – population of disease organism– population of host organism– often complex transgenic relationships
Infectious Disease
• Endemic: always present
• Epidemic: periodically active– Major Epidemics: Pandemics
Infectious Disease
• Epidemic/endemic depends on size of host population– Too small: tendency toward epidemics– Large enough: tends to be endemic
Infectious Disease
• Tendency for ecological balance between disease organisms and their hosts
• Very deadly diseases– kill their hosts too quickly to spread efficiently– but modern communications can change that …
Anthropological speculation
• Humans evolved in Africa
• Human population designed to be naturally regulated by the diseases of Africa
• Take humans out of Africa:– Epidemic growth of human population
• Humans as an epidemic?
Black Death Pandemic 1347-1350
• Bubonic plague
• Killed 50 million Europeans in 3 years – 1/3 of European population
• Severe social disruption– Weakened the feudal system
Population of London, England
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Black Death Pandemic 1347-1350
• Western Europe in population crisis by 1347– war, famine, disease, harvest failure– soil exhaustion
• Black Death the latest of a series of calamities
• Population took until 1600s to rebuild
1918-19 Influenza Pandemic
• WW1: killed 9 million in 4 years
• Influenza: killed 25-37 million in 2 years– 16 million killed in India
Plague in the USA
• San Francisco 1909
• New Orleans 1914
• Now endemic in California– transgenic shift from
rats to ground squirrels
Promoting/Discouraging Disease
• Increase probability of infection– population builds resistance– example of Tuberculosis in Victorian England
• Decrease probability of infection– population does not get the exposure to build
resistance– example of Polio
Biological limits
• People suffer irreversible deterioration and death if internal body temperature– falls below 26 degrees C– rises above 40 degrees C
Extreme Cold
• Windchill, hypothermia– severe high-latitude/high-altitude weather
conditions– cold water exposure
Extreme temperatures
• Cold weather kills fewer than hot weather– easier to keep warm than keep cool– body designed to survive cooling better than
overheating
Extreme temperatures
• Dec 1983 cold snap kills 150 in USA
• 1979-80 5000 heat deaths in USA
• 1936-75 20,000 died in USA from heat & humidity
Extreme temperatures
• Kills the elderly, those with compromised circulatory & respiratory systems
• Urban areas worse: heat island effect, worse in inner city
• Set to worsen with global warming
Extreme temperatures
• 1955 heat-wave in LA killed 946 people– twice as deadly as 1906 San Francisco
earthquake
Frost Hazards
• Bad for agriculture, especially tender crops close to harvest time
• Various devices to reduce frost risk
• Locate farms to avoid frost
The Niagara Fruit Belt
• Mainly on the Lake Ontario plain, N of the Escarpment
• Cooler temperatures here retard fruit growth, reducing risk of a spring frost
• Or make ice wine
Wildfire Hazards
• Promoted when fuel accumulates (dry vegetation) and meets dry, windy, warm weather
October 1871 USA
• Wildfire in Michigan & Wisconsin
• Follows 14 week drought
• Land-clearance fires whipped up by strong winds
• Burns 1.7 M hectares
• Kills 1500
• World’s greatest wildfire disaster?
Ash Wednesday 1983
• Victoria & South Australia
• 1983 El Nino drought & heatwave
• Strong winds (70 km/h+)
• Killed 76, 8000 homeless
NSW Fires Dec 1993-Jan 1994
• 1992-3 El Nino
• Affected 1 M Hectares
• 300+ fires along 1100 km coastline fanned by strong winds
• Destroyed 200 buildings
• Killed 4
Australian Fires
• Burn faster than other people’s fires– 800 Hectares/hour in Australia– 1 Hectare/hour in Northern USA
Causes of “Wildfires”
• Lightning strikes
• Human carelessness– rubbish that burning gets out of control– car exhausts, discarded glass containers etc.,
• Fires maliciously set
• Effects of urban growth
Grass & Brush Fires, Brampton ON
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Fuel Issues
• Fire is part of the natural ecology
• Controls fuel accumulation
• Requires fuel accumulation– tends to be seasonal– Toronto area:
• first warm weekend (usually April)
Effects of Fire Prevention
• May cause fuel to accumulate to dangerous levels
• Pre-emptive burns, controlled burns required
Some areas fire-prone
• Malibu California– Seasonally-dry Chaparral vegetation which
burns hot and fast– Seasonally strong Santa Ana winds can whip up
fires into a conflagration– Inhabited by the rich, dislike restrictions on
their lifestyle– Demand good fire protection