Transcript PowerPoint - Susan Schwinning

The 20th century was a time of accelerating global change:
4 “spikes” of global change
• the human population spike
• the consumption spike
• the carbon dioxide/global temperature spike
• the extinction spike
time
Animated map
Human
Population clock
Future Population Growth
Geographic Distribution of Human Consumption
Per-capita
consumption
UNEP statistics
Increases in per-capita consumption is driven by
developing countries
The “new consumers”:
New consumers are persons with purchasing power of at least
$2,500 per year.
In 2000, the number of recently emerged “new consumers” was
estimated at 1 billion. They join 850 million long-established
consumers.
Most new consumers come from developing or transition
countries.
(China, India, Indonesia, Brazil, Russia, Mexico, Philippines, Turkey, Thailand….)
Most significant environmental impact comes from:
• diet shift towards meat (8 kg grain per 1 kg beef)
• cars
Myers and Kent, PNAS, 2003:
1.28 billion cattle occupy nearly 24 percent of
earth’s landmass.
They weight more than the entire human
population.
• Forest converted to pasture or production of cattle feed.
• Desertification of marginal rangelands in semi-arid and arid regions.
• Production of greenhouse gases (CO2, methane, nitrous oxide).
• Decreased water quality through runoff from fertilized fields and feed lots.
• Introduction of invasive species.
The carbon dioxide and associated temperature
spike took off in the early 20th century
The species
extinction spike
Extinctions
Number sof species eliminated world-wide per year
Biologists surveyed by the Museum of Natural History (NY)
say that current extinction rate exceeds last mass
extinction event, when dinosaurs died.
Global warming. World temperature highest in
human history. Migratory animals begin to die off.
Over 100,000 slash and burn fires set each year. Tropical
forests lost at a rate of one football field per second.
Three species extinctions per hour.
Rapidly accelerating habitat destruction, connecting
previously isolated ecosystems, allowing bioinvasions
The Green Revolution kills off crop diversity and
decimates wild pollinators and soil microbes.
The Age of Exploration: millions of birds, seals and
porpoises slaughtered by European hunters, hundreds of
species lost.
Half of forest cover destroyed after the Agricultural
Revolution.
“God’s Last Offer”, Ed Ayres, 1999
What about mass extinctions?
Cretaceous-Tertiary
Date: About 65 million years ago
Death Toll: Up to 75% of marine
genera; 18 percent of land
vertebrates, & the dinosaurs
The other major extinction events in earth history:
Late Triassic
Date: About 200 million years ago
Death Toll: 52% of marine genera
Possible Causes: Severe
volcanism; global warming
Late Devonian
Date: About 365 million years ago
Death Toll: 55 percent of marine genera
Possible Causes: Global cooling; loss of
oxygen in oceans; impact
Late Ordovician
Permian-Triassic
Date: About 440-450 million years ago;
Date: 286-248 million years ago;
Death Toll: 84% of marine genera; Death Toll: 60 percent of marine genera
90-95% of marine species; 70% of Possible Cause: Dramatic fluctuations in
sea level
land species.
Possible Causes: Asteroid or comet
impact; severe volcanism; dramatic Late Pre-cambrian
Date: About 650 million years ago;
fluctuations in climate or sea level
Death Toll: most unicellular organisms
Possible Cause: O2 enrichment of
atmosphere.
Just some of the hundreds of similar headlines:
One Quarter Of All Mammal Species Face Extinction Soon
(IUCN-- 2000)
Monkeys, Apes Are Being Eaten to Extinction (Associated
Press)
Mass Extinction of Freshwater Creatures Forecast (WWF
Report)
90% OF ALL LARGE FISH GONE FROM WORLD'S
OCEANS (Nature-- 2003)
North Sea Undergoing Ecological Meltdown (U.K.
Independent)
Amphibians Declining Worldwide (Boston Globe)
Reptiles Vanishing Faster Than Amphibians (CNN)
Migratory Birds and Animals Rapidly Dying Out (Environment
News Service)
Forests Face Global Extinction (United Nations)
1000's Of Medicinal Plants Being Harvested to Extinction
(Australian Broadcasting Co.)
25% Of World's Conifers Threatened With Extinction (IUCN)
One in Eight Birds Face Extinction (BirdLife International)
90 Percent of Great Ape Habitats Will Be Destroyed by 2030
(United Nations)
…
The Pleistocene extinction (of the last ice age) was different
from previous mass extinction events:
1. Selective disappearance of megafauna.
2. Occurred at different times on different land masses.
3. Previous ice ages did not result in similar extinctions.
1. Selective disappearance of megafauna:
Species loss across America, Europe and Australia:
100% of herbivores > 1000 kg
75% of herbivores 100-1000 kg
41% of herbivores 5-100 kg
< 2% of herbivores < 5kg
2. Occurred at different times on different land masses.
Megafauna extinctions
in % species lost
The extinctions coincided with
the arrival of human hunters
and gatherers to continents...
Except Africa!
Species numbers are declining on land and in aquatic systems
World Wildflife Fund estimates
The current extinction rate is orders of magnitude higher than the
long-term average extinction rate.
Source Millenium Ecosystem Assessment
Total Number of threatened species by continent
Source: EarthTrends 2007, using data from the IUCN Red List of Threatened Species 2007.
The cucumber tree, Yemen
Kirtland's Warbler
Anegada Ground Iguana, Virgin Islands
Mountain Gorilla
Central Africa
Cycas transachana, Thailand
Ambositra Palm Madagascar
Biodiversity Hotspots
The Atlantic Coastal
Rainforest of Brazil
(450 tree sp./ha. highest richness on
earth)
1945
85.4% of Bahia
state was forest.
1960: 50% left.
1974: 25% left.
1990: 6% left.
The multiple impacts of humans on biodiversity and
ecosystems:
•
Overexploitation of game animals.
•
Purposeful setting of fire to manipulate the movement
of game animals.
•
Clearing of natural ecosystems for agricultural
production.
•
Introduction of non-native species.
•
Overfishing.
•
Pollution: new inputs into material cycles at a global
scale (nitrogen, carbon dioxide, pesticides, …).
Causes of recorded vertebrate extinctions:
Spike 1
Human population size
Diet and lifestyle
changes of “new
consumers”
Spike 4
Spike 2
Loss of biodiversity
Consumption
Over-exploitation
Pollution
Habitat loss
Fossil fuel burning,
Slash & burn of old forest
Fertilizer production
Rapid
climate changes
Spike 3
CO2 and other
greenhouse gases