Environmental Science 1021F/G Lecture Notes - Lecture 7: Eutrophication, Marine Atlantic, Water Cycle
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9 Nov 2011
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ES1021G Lecture 7: February 15, 2011
Renewable Resources
Overview:
•Characteristics of renewable resources
•Major classes of renewable resources
•Resource degradation: overharvesting
•Characteristics of renewable resources
•Major classes of renewable resources
•Resource degradation: overharvesting
Characteristics:
•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
Important Note: Reliance on renewable resources is a core attribute of a
sustainable economy; one that can run forever without depleting its essential
base of natural resources.
Major kinds of renewable resources:
•Fresh water : recharged through the hydrological cycle
•Agricultural resources: crops and site capability
•Forest resources : timber
•Hunted animals : whales, seals, fish, deer, waterfowl
•Sunlight (in its various manifestations): (see Chapter 13)
•Passive solar
•Wind
•Flowing water
•Biomass
•Photovoltaics
Freshwater
•Groundwater
•Occurs in aquifers – underground reservoirs
•Used by many rural people and by urban utilities without access to
abundant river flow or lakes
•Surface water
•Occurs in lakes, rivers and wetlands
•In general, freshwater is abundant in Canada
•Exception: some arid regions
•Water quality is sometimes poor. This may be due to natural salts,
eutrophication, or contamination by fecal pathogens from livestock
Agricultural resources
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ES1021G Lecture 7: February 15, 2011
•Site capability – influences crop productivity
•Climatic conditions are important
•Tilth – related to soil structure and organic content
•Plant Crops
•Key grains: wheat, oats, barley, maize
•Others: soybean, canola, potato
•Forage crops for livestock
•Animal crops
•Key species: cow, sheep, pig, chicken, turkey
•Most are raised intensively on ‘factory farms’
Forest Resources
•Forest area – only ½ of global forests are left
•Will likely be again halved in ~50 years
•Deforestation – mostly occurs in tropical countries
•Timber harvesting
•About 1-million ha/year in Canada
•95% by clear-cutting (in 2006)
•Wood used to manufacture lumber or paper, or as fuel
•Forest management
•39% of harvested area planted with seedlings; the rest is natural
regeneration
•Plantations (tree farms) are most intensively managed
Fish Resources
•Marine fisheries – most of the world’s most important fisheries are now badly
degraded
•Also in Canada – such as badly depleted stocks of cod in the Atlantic,
salmon in the Pacific
•The damage is mostly caused by over-fishing; ‘mining’ the fish
•Aquaculture is the application of an agricultural model
•Freshwater – trout and other fish
•Marine – Atlantic salmon, several shellfishes
Hunted Animals
•Whaling – now mostly illegal
•Right whale and blue whale still critically depleted
•Other species have recovered somewhat or totally (grey whale)
•Sealing – still a large hunt of abundant harp and hooded seals
•Terrestrial hunting – >470,000 deer per year, plus bears and others
•Waterfowl hunting – ~2.2 million ducks and geese per year
Resource Degradation: overharvesting and mismanagement
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ES1021G Lecture 7: February 15, 2011
•There are many examples of the irresponsible ‘mining’ of potentially renewable
resources
•Most were caused by ‘greedy’ over-harvesting (at a rate that exceeded
regeneration)
•In some cases, mismanagement of the regeneration was also an problem
Prominent examples:
•Depletion of whale stocks by unfettered whaling (now mostly illegal)
•Depletion of many seal stocks (now mostly recovered)
•Collapse of most of the important marine fisheries, e.g., cod in Atlantic
Canada, Pacific salmon in British Columbia, bluefin tuna everywhere
•Depleted populations of many game species – hunted mammals and
waterfowl
•Deforestation – now mostly a tropical problem
•Degradation of agricultural site capability
Canada’s Resource Base
•Fresh water – mostly abundant, but at great risk from climate change (loss of
glaciers and less precipitation)
•Agricultural resources – mostly healthy, but widespread moderate salinization
and at risk from climate change and drought
•Forest resources – still abundant, but shortages in some regions and rapid
depletion of old-growth forest
•Hunted animals – mostly abundant, but some species are depleted
Renewable Resource Mining Case Study: The Commercial Cod Fishery
•Atlantic cod once supported a great world fishery
•The fishing was essentially unregulated, and the stocks became badly
depleted
•In 1977, Canada declared a 320-km management zone, and the stocks
somewhat recovered
•But then there was a further and larger collapse, even under the
regulated regime
•A moratorium was enacted in 1990, but the cod have not recovered
•The collapse of cod was caused by voracious over-fishing, mostly by Canadians
Renewable Resource Mining Case Study: The Commercial Whale Hunt
•Commercial whaling was voracious – it brought several species to the edge of
extinction
•Such as right whale, bowhead, blue, humpback, grey
•A ban on commercial whaling began in 1986
•Some species recovered – e.g., grey and humpback
•Others remain critically depleted – right and blue
•Japan, Norway, & Iceland are still doing ‘scientific whaling’
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