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Transcript
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”