Transcript - Catalyst

TESC 211
The Science of Environmental Sustainability
Autumn 2011UWT
Species extinctions are a natural process and through out most
of Earth’s history have occurred at an average rate of 0.0001%
per year.
“Extinction is forever”
There have been five mass extinctions when 50-95% of species
became extinct within a relatively short period of time.
Recovery of biodiversity from a mass extinction event typically
takes several million years.
Extinction is often categorized as being of one of three levels:
• Local extinction
• Ecological extinction
• Biological extinction
Local extinction
• no longer found in an area
• found elsewhere
• loss of one or more populations
e.g. Arctic fox has not been found in the British Isles for ~12,
000 years but is found through out northern Europe
Ecological extinction
• reduced population size
•no longer able to perform function in ecosystem
e.g. American Bison once dominated the grasslands of North
America, now most of cultivated in captivity for hides and meat.
Biological extinction
• species can no longer be found anywhere
•Irreversible loss of natural capital
e.g. Thylacine (Tasmanian tiger), Dodo, Tyrannosaurus Rex,
Homo Habilis.
It is estimated that current extinction rates are at least 100 times
greater than the back ground extinction rate.
Why?
• Human activities have disturbed ~50% of the Earth’s surface
water
• Human activities have disturbed 50-80% of the Earth’s land
surface.
Anticipated that by the end of the century extinction rate
will reach 0.1% - 1% (1000-10,000X background rate)
A t a 1% annual extinction rate:
• within a century >50% of all species would be lost
100
90
% Species
80
70
60
50
40
30
0
20
40
60
80
100
Years
It would take 200, 000 human generations to recover these
species.
• 20 times longer than humans have occupied the planet
Why be concerned about extinctions and loss of
biodiversity?
• Species provide economic and ecosystem services
• 62% of all cancer drugs derived from tropical forest plants
• Food
• Raw materials
•Pest control
•Eco-tourism
• Lion skin ~$1000
• Lion sighting tours $500, 000
• Intrinsic value, quality of life etc
What speeds up the rate of extinctions?
The most significant causes of extinctions can be summarized by
the acronym HIPPCO:
• Habitat
• destruction, degradation and fragmentation
HIPPCO:
• Invasive species
• deliberately introduced
• accidently introduced
What speeds up the rate of extinctions?
HIPPCO:
• Population
• increased demand on ecosystem services
• more land diverted to human uses
“SEVEN billion people will call planet Earth home from this Monday
(10/27/2011). That is the projected date at which the number of people
alive will pass the seven-billion milestone, according to a landmark
study of global population pressures released overnight by the UN
Population Fund.”
Mark Kenny, The Advertiser 10/27/2011