Environmental Science 1021F/G Lecture Notes - Lecture 7: Eutrophication, Marine Atlantic, Water Cycle

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ES1021G Lecture 7: February 15, 2011
Renewable Resources
Characteristics of renewable resources
Major classes of renewable resources
Resource degradation: overharvesting
Characteristics of renewable resources
Major classes of renewable resources
Resource degradation: overharvesting
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
Flowing water
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
Plantations (tree farms) are most intensively managed
Fish Resources
Marine fisheries – most of the world’s most important fisheries are now badly
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
Most were caused by ‘greedy’ over-harvesting (at a rate that exceeded
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
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
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
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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