Review 3.6-3.8
3.6 Water Resources
•2.5% of the Earth’s water is fresh water.
–70% of that is ice caps and glaciers
–Almost 30% is ground water
–Remainder is lakes, rivers, soil water, atmosphericwater vapor, and biota
–Direct access to only 0.3% of the total.
–Atmospheric water vapor is only .001%
–All together referred to as the HYDROSPHERE
Turnover Time
•Time it takes for a water molecule to traverse thewater cycle (hydrologic cycle)
–Longest turnover time: a molecule in the polar icecaps
–Shortest turnover time: biological water
–If water is turned-over within a year, it is a renewableresource.
–Ground water is not renewable
–Drilling wells in Aquifers, while producing a lot ofwater, leads to depletion of a non-renewableresource.
Sustainable water use:
•Cities:
–More efficient buildings—use of recycled rainwater for showers and sanitation
–Water efficient appliances
–More meters to help people use it more efficiently
•Rural areas:
–Drought resistant crops
–Use organic fertilizer to prevent eutrophication ofthe water
How water is used:
1=domestic
2=industrial
3=agricultural
Think about how Ecocentric vs Technocentricphilosophies are involved in water usageprojects.
Supply and Demand
•Irrigation
•Industry
•Increase population
•Global warming
Aquifer loss
•US: Kansas High PlainsAquifer
•Other countries usingthe water for irrigationof agriculture: Australia,Mexico, Spain and US
•France: loss of water tonew agriculture
•Saudia Arabia overpumps water
•India—lots of loss foragriculture
3.7 Limits to Growth
1.population
2.natural resources
3.pollution
4.agricultural production
5.industrial production
Limits toGrowth Model
•Food induced outputand population growexponentially untildiminishing resourcesslow industrial growth.
•Population andpollution continue.
•Population growth ishalted by increaseddeath due to lack ofresources.
•If present trendscontinue, limit togrowth in 100 years.
Limits toGrowth Model
•BUT: this is world wide.
•Ignores spatialdistribution ofpopulation, resources,etc.
•Alternative:SUSTAINABLE LIMITS TOGROWTH
Sustainable Limits to Growth Model
CarryingCapacity
For large populations,
Stops once it hits the cc
Small pops, short lifespans, high
Fertility.
Can’t determine Human CC
•The range of resourcesis great
•Humans can substituteresources
•Lifestyle can change
•Technology
•Importing of resources
Malthus
•Population growsexponentially
•Food increases linearlybut will not be enough.
Boserup
•In preindustrial society,new technology willlead to increased foodproduction.
•Shifting cultivation—land only last 100 years
•Multi cropping—morethan one crop per year.(more advanced too)
Increased food producition
•Drained marshes
•Reclaimed land fromsea
•Cross bred cattle
•High yield plants
•Terracing
•Greenhouses
•Irrigation improvements
•New foods
•Artificial fertilizers
•Farming native species
•Fish farming
3.8 Environmental demands on humanpopulations
•Ecological Footprints
•--an area of land andwater required tosupport an individual orpopulation.
•Opposite of CarryingCapacity
IncreasedFootprint
•Fossil fuels
•Technology dependence
•Imported resources
•Per capita foodconsumption high
•Meat rich diets
•Reduced resource use
•Recycling
•Reusing
•Improved efficiency ofresource use
•Decreased pollution
•Export of wastes
•Increased CC due totechnology
•Import of resources
•Using technology toincrease land use
Decreased
Footprint
Calculating Footprints
1.Per capita foodconsumption (kg yr-1)
Mean food production oflocal arable land (kg ha-1yr-1)
Large meat consumptioncauses higher grainconsumption (food)
1.Per capita CO2emission (kg C yr-1)
Net carbon fixation oflocal vegetation (kg C ha-1yr-1)
•TOTAL LANDREQUIREMENT = sum ofboth equations.
Does not include:
•Aquatic or atmosphericresources
•Wastes other than CO2
•Land in other countriesfor imports
•Replacement ofproductive land forcities