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3.3 - The Importance of Biodiversity

3.3 - The Importance of Biodiversity. only about 1.5 million of a possible 100 million species on Earth have been described biodiversity is the most important measure ecosystem health

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3.3 - The Importance of Biodiversity

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  1. 3.3 - The Importance of Biodiversity • only about 1.5 million of a possible 100 million species on Earth have been described • biodiversity is the most important measure ecosystem health • biodiversity is highest in tropical rain forests straddling the equator (283 tree species per hectare vs. 15 in Ontario, 200 hummingbird spp. vs. 1) • rainforest experiment: 10% of insect species from a single tree were known, same result for any tree, but a different 90% had never been described!

  2. Biodiversity Under Attack • many scientists believing we are undergoing the 6th great extinction • five previous extinctions have had natural causes like volcanic eruptions or meteorites, but this is the first to be the result of the actions of one species • species extinction is like the burning of a great library whose books have yet to be read • the major cause of extinction is habitat loss through deforestation, urbanization, industrial agriculture, pollution, and climate change

  3. Just a few extinct species in Canada Passenger Pigeon (Great Lakes/St. Lawrence Ecozone) Great Auk (Atlantic Marine Ecozone) Sea Mink (Atlantic Maritime Ecozone) Eskimo Curlew (Grasslands Ecozone) • when humans first encounter new species, they often overexploit them • 80 species of mammals and birds became extinct soon after humans reached North America 10 000 ya, including the sabre-toothed tiger, mammoths, camels, horses, and sea cows • in the past 400 years, 700 vertebrate species have become extinct, including 12 in Canada in the last 170 years (see Figure 4, P. 84) • humans depend on other species far more than they depend on us • if humans disappeared from Earth, it is estimated that within 50 000 years, natural ecosystems would repair themselves and no trace of human existence would remain

  4. Species at Risk • ecological consequences occur long before species become extinct • when a population declines below a critical level, the species can no longer fill its ecological niche, which effects the biotic and abiotic factors of the ecosystem • in Canada, the status of species is monitored by the Committee on the Staus of Endangered Wildlife in Canada (COSEWIC) • members from government, universities, NGO’s, and First Nations use data from species at risk to place them in one of 4 categories (not including extinct): • special concern • threatened • endangered • extirpated • if endangered or threatened, an action plan must be prepared to ensure the recovery of the species

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