Human Population Growth
Little to no change for the first 200,000 years
Deaths rates decrease due to agriculture (1950s Green Revolution), domesticated animals, enabled permanent cities/towns, healthcare, and Industrial Revolution
Births rates stayed high
Population now growing exponentially Population reaches 8 billion on Nov. 15th, 2022!
Demography
the study of human populations
Population growth in the US, Canada, Japan, China, and Europe, has SLOWED because of
The Demographic Transition
The Demographic Transition Phase 1:
death rates fall, birth rates don't. Pop. grows exponentially
The Demographic Transition Phase 2:
population gets wealthier, educates. Birth rates drop, pop. growth slows/stops
"The Tragedy of the Commons"
when a resource (anything with value) is free to use but unregulated, humans tend to use it up as quickly as possible until it is depleted
Resource Types
Nonrenewable -coal, oil, natural gas - millions of years to form
Renewable -wood, water, sun, wind, air (but are these all really renewable??)
Environmental Problems (there are 7 main ones)
Freshwater Depletion
Polar Ozone Holes
Desertification
Deforestation
Climate Change
Overfishing
Biological Magnification
Freshwater Depletion
a. Pollution and overuse of groundwater - hundreds of years to regenerate b. deforestation/overfarming/grazing erodes soil, creates desert conditions (soil can't hold water) c. 75% of US water is used for agriculture
Freshwater Delpetion Solutions
-drip irrigation -protect the wetlands, which purify H2O and "recharge" groundwater
Polar Ozone Holes
a. Caused by aerosol can CfC's being released in atmosphere b. Open every summer, close every winter c. Increased UV rays harm living things *Not to be confused with climate change
Polar Ozone Holes Solutions
-CfC's are banned --> Holes have started shrinking!
Desertification
a. Farming and overgrazing causes heavy erosion, resulting in soil losing ability to hold water
Desertification Solutions
-crop rotation -grazing area rotation -leave plant roots in the ground after a harvest -Contour farming
Deforestation
a. 80% of old-growth forests (nonrenewable), have over half of the tree cover gone b. Erosion and habitat loss, increase in CO2, decrease in watersheds
Deforestation Solutions
-selective logging -tree farms -faster-growing GMO trees
Climate Change
a. CO2 at highest in 650,000 years b. Since 1880, the temperature increased nearly 1C c. Droughts more frequent and severe (led to more forest fires) d. Severe hurricanes, up to 75% since 1970 e. Snow cover, sea ice, glaciers, and ice caps declining worldwide f. Sea levels increasing worldwide (4-8 in. since 1990) g. Ocean temps and ocean CO2 concentrations increasing h. By 2050, global temps. will rise ~2
C
Overfishing
a. Many food fish are nearly depleted (salmon, halibut, cod, crab, etc) b. International waters (T.O.C.)
Overfishing Solutions
-close certain areas to fishing -aquaculture (fish farms)
Biological Magnification
a. Toxins like DDT and Mercury become more concentrated as they move up food chains b. "rule of 10%" - energy is lost, but certain toxins are not c. As much as ten times more toxin from one trophic level go to the level above