Environmental Science 1021F/G Lecture Notes - Lecture 6: Sustainable Development, Potash, Candu Reactor

21 views10 pages
Page:
of 10
ES1021F Lecture 6 (Week 7) – October 26
Freedman Chapters 12 & 13
Renewable vs non-renewable natural resources
Non-renewable resources are finite, and do not regenerate – they can only be ‘mined’
As they are used, they are used up
Their stocks are determined by the rates of discovery and of mining, and economic
factors affecting profit
However, the lifespan of some non-renewables can be extended by recycling
Time scales (Ex. Trees, oil)
Examples of non-renewable resources:
Metals
Fossil fuels
Petroleum
Natural gas
Coal
Oil-sand
Renewable resources have the ability to regenerate after they are harvested
Potentially, they can be harvested forever without depletion
The key is to not harvest them faster than their regeneration, or to otherwise
mismanage them
Examples of renewable resources:
Forest biomass
Fish, deer, and other ‘hunted’ animals
Sunlight in all of its manifestations
Flowing water
Wind
Biomass
Photovoltaics
Passive solar
Renewable resources can regenerate, thus they are the fundamental basis of a
sustainable economy; one that can run forever without depleting its resource base.
Non-renewables also have a role in a sustainable economy, but only if their depleted
stocks are made up by equivalent increases of renewable resources:
For example, consider a power plant that generates electricity by burning coal
The depleted potential energy of coal can be offset by fostering an equivalent net
increase of forest biomass
ES1021F Lecture 6 (Week 7) – October 26, 2011
Emitted CO2 can be offset by a net increase in organic-carbon in tree biomass
Appropriate management can increase the potential harvest of biological
resources
Biological resources include forest biomass, hunted animals, and agricultural crops
Biological resources can be enhanced by various kinds of management actions, which
increase productivity, conserve existing biomass, or enhance quality
***How do you determine the yield/stock of a biological/renewable resource?
Management can increase biological resources
Selective breeding and domestication can develop crop varieties that are much
‘improved’ in cultivation over their wild progenitors
ES1021F Lecture 6 (Week 7) – October 26
Post-harvest regeneration can be enhanced by planting young stock, growing
perennial crops, and fostering good conditions for recruitment
Growth rate can be increased by reducing competition, adding fertilizer or water, and
controlling pests
Natural predators of livestock can be controlled
Degradation of renewable resources
Deforestation is a widespread problem
Half of Earth’s original forest cover is now gone
Another half may disappear in the next 50 years
Deforestation is mostly caused by the conversion of forest to agricultural land
Timber harvesting and urban conversion are also important
Deforestation is a terrible problem:
Loss of a renewable resource – timber
Damage to forest biodiversity
Loss of ecological services (e.g., erosion control)
Severe depletion of fish stocks has become common throughout the world’s oceans
Loss of cod stocks in Atlantic Canada
Depletion of salmon runs in British Columbia
This damage is caused by several factors:
Over-fishing – catch rates that exceed regeneration
Damage caused to breeding rivers of salmon
Depletion of fish stocks is a terrible problem:
Loss of a renewable resource – fish as food
Damage to biodiversity – by-catch and other problems
Degradation of ecological services (e.g., salmon bring oceanic nutrients to the land)
Same format as deforestation, fishstocks
Excessive water withdrawals are depleting fresh water in many areas
Groundwater is being rapidly ‘mined’ in arid regions
The flow of some rivers is being reduced, or the hydrology modified, or the water
polluted
This damage is caused by several factors:
Excessive withdrawals for irrigated agriculture
Use for cities and industry is also important
Pollution by agricultural and industrial chemicals
Depletion of water reserves is a terrible problem:
Loss of a renewable resource – water is crucial