Download Extinct

Loss of Biodiversity
EXTINCTION - the disappearance of a species
Extinctions have been occurring constantly at a
low 'background rate', usually matched by the rate
at which new species appear - resulting in an
overall increase in biodiversity
Imagine a world without extinction -it would be
really crowded!!
Extinction Examples
• ‘Cambrian Explosion’ (rapid increase in
biodiversity 500 million years ago) was
followed by a small extinction including
loss of many trilobites (¯diversity)
• cause unknown - possibly sea level
change
Mass Extinctions
• There have been 5 major extinctions since the
beginning of life 3.5 billion years ago
• 1. End of Ordovician (440 mya) probably due to
glaciation
• 2. Late Devonian (365 mya) possibly due to
global cooling since many warm water species
were lost
• Over 500,000-15 million years
• 3. Permian (250 mya) - biggest extinction
– estimated that as many as 96% of all marine
species were lost and on land, 3/4 of all
vertebrate families became extinct
– Possible causes
• continents merging to form Pangea disturbing
marine and terrestrial habitats
• volcanic eruptions - ash and CO2 released caused
global warming
• 4. Late Triassic (200 mya) - loss of about
1/4 of families due to climate change
(possibly increased rainfall)
– This loss of biodiversity provided opportunities
for dinosaurs to exploit
• 5. Cretaceous-Tertiary (K-T) - extinction
of half of all marine species, many
terrestrial plants and animals including the
dinosaurs (65 mya)
• Possible causes:
– Impact hypothesis - meteorite 10 km in
diameter collided with the earth disrupting
ecosystems
– Volcanic activity in “India” released material
that blocked sunlight Ô earth became cooler
Non-human causes of extinction
• Volcanic events
• Ocean temperature change
• Sea level changes
• Meteorites
• Glaciation
• Global climate change
• Competition / predation
Human causes of extinction/loss of
biodiversity – HIPPO
• Habitat destruction
• Introduced species
• Pollution
• Population
• Over consumption
Habitat destruction
• Degradation
– e.g. stream siltation caused by deforestation
• Fragmentation
– e.g.highways through national parks
• Loss
– e.g. Pasakpoo slopes in Calgary (Bronwyn)
– e.g. new hospital in Edinburgh (Fiona)
Introduced species
• Non-native species
– e.g. green crab, zebra mussel, ctenophore in
Mediterranean Sea
• Genetically modified species
Pollution
• Air
• Water
• Land
• Major sources:
– Fossil fuels e.g. Shoreham Power Station
– Domestic waste
– Industrial waste
– Manufacturing processes
– Agriculture
Population
• With the global population increasing at a
rate of 3 people per second there is:
– Increasing use of resources
– Increasing habitat destruction
– Increasing waste production
Over consumption
• Hunting, collecting, harvesting
– e.g. Atlantic cod for food
– e.g. sea otter for fur
• Wildlife trade e.g. bear gallbladders as
aphrodisiacs
• Indirectly through over consumption of
resources e.g. water, land
Are we on the verge of a sixth mass
extinction?
Sixth mass extinction?
• Background extinction rate:
– Ten to 100 species per year
– 3-5 families per million years
• Mass extinction rate
– > 10 families per million years
• In past 200 years the extinction rate has been 20
to 50 (to 10,000) times greater than background
mostly due to human activities (HIPPO!)
Sixth mass extinction?
• 15,000 to 100,000 species extinctions every
year (Estimated)
• Estimated loss of 27,000 species per year from
rainforests alone
• If we assume that there are 10 million species
on the planet, it would only take about 560 years
for 95% to go extinct at the present rate
Does it matter if there is a sixth extinction?
• Won’t biodiversity recover?
• Do we value biodiversity?
Categories (IUCN + COSEWIC)
• Extinct - no reasonable doubt that the last individual has died (no
records in 50 years)
• Endangered - a species facing imminent extinction or extirpation
• Extirpated - a species that is gone from an area but still exists
elsewhere
• Threatened - a species likely to become endangered if the factors
affecting its vulnerability are not reversed
• Vulnerable - at risk due to declining population but not threatened
• Unknown - insufficient data
• Not at risk - species was evaluated and found not to be at risk
BC lists
• Red list - include extirpated, endangered or
threatened species
– e.g. Steller sea lion, double crested cormorant
• Blue list - includes vulnerable species (species
of concern)
– e.g. grey whale, great blue heron
• Yellow list - includes species which are
uncommon or show declining populations
– e.g.river otter, belted kingfisher
Characteristics of vulnerable species
• Small population size - island species
• Small population size - species with limited
habitats
• Extremely specialized species
• Species with low reproductive potential
• Species that require large territories
• Species with limited dispersal ability
Vulnerable species - continued
• Migratory species
• Species that are economically valuable or
hunted for sport
• Predators
• Species that are vulnerable to pollution
• Species that are incompatible with civilization
Species approach to conservation
• Strengths
• Weaknesses
Coelacanth
• thought to have vanished from the fossil
record around 70 million years ago
• living coelacanths were found living off the
Comoro Islands in the Indian Ocean in
1938
• 50-500 rule for the genetic health of
populations - population of 50 or more is
adequate for the short term only, and one
of 500 is needed to keep the species alive
and healthy into the distant future
- E.O. Wilson “Diversity of Life”