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”