Lecture: Chapter 28 - Population growth, Resource use, Sustainability Flashcards
Dilemma: Resources are running out
Earth’s resources are limited
Human population size si growing exponentially
Human population
Overpopulation
Current estimate 6.5 billion, in 2050 9.5 billion
Huge demand on resources and space
Human conflict
Reasons for rate of resource consumption
Human population size Consumption rate (per capita)
Natural capital
Includes a range of natural resources such as : Forests, grasslands, nutrients, air, water, soil, organisms
Why do we rely on biodiversity?
Food Fuel Fiber Medicines Building materials
Sustainable yield
Sustainable resource use requires a balance between supply and demand
Sutainable yield: Harvest rate = biological growth rate
Yield
Amount of resource harvested per unit of time
Ecosystem services
Processes by which the environment generates resources/natural capital
Agriculture
Provides the majority of resources for humans
Replaces native habitats and diverse natural ecosystems with man-produced single crop fields (monoculture) or fields with few crops (polyculture)
Two main types:
Industrialized
Traditional
Industrialized agriculture
Large energy inputs
- fossil fuels
- chemical fertilizers
Litter human and draft animal labor
Efficient, economical mechanization
Specialized machines for each crop
Mainly in developed countries in temperate zone
Consequences of industrialized agriculture
Leaching
Need for fertilizers
Monoculture (pest, disease outbreaks)
Tilting soil (water erosion)
Eutrophication
Nutrient enrichment.
Nutrient poor lakes with low primary production are oligotrophic
Traditonal agriculture
Subsistence agriculture - for family units survival
Little energy input - mainly human and animal labor
Shifting/swidden agriculture
Tropics
Clears forest for cultivation
Resulting ash is nutrient rich
Gradual decline in soil nutrient content after each harvest, need to abandon after a few harvests to allow time for fallowing
Options to increase agricultural production
Increase land area of agricultural production
Increase food production per unit area
We depend on industrialized agriculture but we need to make it sustainable. What is the solution?
Get benefits without negatively impacing the environment
Maintain productivity while conserving resources
Soil conservation methods
Minimize wind and water erosion
- little or no tilling
- planting shrubs and trees as wind breakers
Reduced use of pesticides
Control pest, disease outbreaks
- crop rotation
- use multiple crops in strips
Alternate sources of soil nutrients
Alternatives to chemical fertilizers
- manure
- leguminous cover crops
Water conservation
Forest -essential human resource
35% Earth’s surface
- resources from trees
- overharvesting
Forest cover decreases at a high rate
Clear cutting
Large tracts of forest entirely removed
Seed-tree / shelterwood
Few seed-bearing trees elft behind
Exposed land surface to erosion
Selective cutting
Selected tree removal
Fewer trees remove
Accessory roads and trails still destructive
Sustainable forestry
Sufficient rotation timer required for forest regeneration to levels before harvest
Overexploitation of fisheries
Overfishing in the oceans has led to declines in abundance and size of top predators
Maximum sustainable yield in fisheries
Under the density-dependent logistic model, the highest growth rate is at intermediate-sized populations
How can we manage our limited resources?
Optimize harvest by keeping population at intermediate size
