Tenth lecture

Human effects on ecological balance

• Example 1

• Hawks are natural enemies for mice, rats & rabbits.

• If they were eliminated; mice, rats & rabbits would increase in number and ruin the crops.

• Example 2

Pumas, wolves &coyotes prey on deer.• One year, a drive killed these enemies.• Deer multiplied in numbers.• They didn’t have enough food.• Many of them died from starvation.• The others chewed the bark of the trees;

the trees died; the small mammals and birds lost shelter and food.

Human effects on ecological balanceHuman effects on ecological balance

Human effects on ecological balance

• Example 3

• Mongoose was introduced to Jamaica to control rats.

• Mongoose also killed birds, snakes & lizards.

• The cane beetles multiplied & do much damage as rats.

Human effects on ecological balance

• Example 4• In 1862, a few pairs of rabbits were

introduced to Australia. • Within a few decades; there were millions

of rabbits.• They destroyed grassland and crops.• In 1950; A deadly virus, myxomatosis, was

introduced to control rabbits.

Human effects on ecological balance

• Example 5

• In 1916, Japanese beetle, spread rapidly in New Jersey and soon were responsible for loss of millions of dollars’ worth of fruit, crops, lawns and flowers.

Air pollution

• Is the contamination of the air by noxious gases and minute particles of solid and liquid matter (particulates) in concentrations that endanger health

• Air pollution only occurs outdoors

Sources of Outside Air Pollution

• Combustion of gasoline and other hydrocarbon fuels in

cars, trucks, and airplanes• Burning of fossil fuels (oil, coal,

and dinosaur bones)• Insecticides• Herbicides• Everyday radioactive fallouts• Dust from fertilizers• Mining operations• Livestock feedlots

Sources of Indoor pollution

• Efficient insulation• Bacteria• Molds and mildews• Viruses• animal dander and cat saliva• plants• house dust• Mites• Cockroaches• pollen

Effects on the environment

• Acid rain• Ozone depletion• Global warming• In human population- respiratory problems,

allergies, strengthens lugs, and a risk for cancer

What’s in smog?

• particulates (especially lead)

• nitrous oxides

• potassium

• Carbon monoxide

• Other toxic chemicals

Acid rain

• contains high levels of sulfuric or nitric acids

• contaminate drinking water

and vegetation

• damage aquatic life

• erode buildings

• Alters the chemical equilibrium of some soils

CO2

Reflected Light

Re-radiated Heat

CO2

HEAT!

HEAT!Trapped Heat

Cloud, Dust

Greenhouse effect 13