Test 2 Flashcards
What is the world birth rate?
21
What is the world death rate?
9
What is the world growth rate?
1.28%
What is the replacement fertility rate?
MDC= 2.1 LDC = 2.5
What is the total fertility rate (TFR)?
number of children / woman
What percentage of the world is in the pre-productive stage?
18% in MDCs
30% in LDCs
What percentage does immigration add to the population.
about 1%
What percentage of the world has a population rate the is declining?
13% – 38 countries
What are the worlds ecological footprints
MDC = 20 acres / person
LDC = 2 acres / person
US 30.2 acres / person
What is the available amount of space per person?
4.7 available — 5.7 estimated future use = population crash!
mineral percentages in soil?
minerals; 92% silicates (the rest oxides, sulfides, carbonates.
What is an igneous rock?
One formed by cooling and crystallization.
What is a metamorphic rock?
One formed by heat and pressure.
What is a sedimentary rock?
One formed by weathering, erosion, transport, deposit or lithification.
what is physical weathering? Where is it most important?
–ice and frost wedging
–unloading
–crystal growth
–root wedging
–wind
Most important in arid areas
What is chemical weathering? Where is it most important?
–hydrolysis
–acidification
–oxidation
–biochemical weathering4
Most important in humid areas.
What does the rate of weathering depend on?
Climate – tmep. and percipitation
rock type—texture, fractures, composition
what is soil composed of?
rocks and minerals; ., organics, water, air, and critters
–marginally renewable resource
How long does it take to form one inch of soil?
200-1000 years
What is a soil profile?
O,A,E,B,C
Important characteristics of topsoil
nutrients, roots, water, decomposers
Important soil characteristics
- -texture (grain size)-gravel, sand, silt, clay
- -equal amounts is loam
- -porosity—pore space
- -permeability—connections of pores
- -soil structure or sorting—affects porosity and permeability
Contributors of soil erosion
water, wind, humans, gravity
increased by farming and deforestation
Harmful effects of soil erosion
- -loss of fertility and ability to hold water
- -pollution by sediment
- -55% of all cropland suffers some amount of erosion
- -more fertilizer needed
- -earth movement (landslides) more likely
Degradation of soil
- -desertification—10% drop in production
- -causes: climate, overgrazing, deforestation, bad farming
- -40% of all land shows some desertification
irrigation of soil
- -salt buildup from evaporation
- -50% of all cropland shows some salinization
waterlogging
wash salt to groundwater
ways to conserve soil
- -minimum tillage
- -no tillage
- -terracing
- -contour farming
- -strip cropping
- -agroforestry
- -organic fertilizers
Food systems
cropland = 76% of world food rangeland = 17% (meat and dairy) oceans = 7%
