Concise Summary of Extinction and Threats to Biodiversity

  • Learning Outcomes

  • Understand extinction processes: driven extinctions and stochastic extinctions, and define extinction vortex.

  • Explain vulnerability of small populations due to environmental stochasticity.

  • Define mass extinction and context current crisis against historical events.

  • Describe how perfect storms of environmental changes elevate extinction risk, particularly in Australia.

  • Understand IUCN Red-List classification for threatened species.

  • Identify key global factors impacting biodiversity decline.

  • What is Biodiversity?

  • Three levels: Ecosystem Diversity, Species Diversity, Genetic Diversity.

  • Approximately 4 billion species have evolved; 99% are extinct.

  • Extinction

  • Definition: No living members of a species remain. Different types:

    • Extinct in the wild
    • Regionally extinct
    • Functionally extinct.

  • Extinction Processes

  1. Driven Extinctions
    • Caused by critical environmental changes.
    • Common causes: habitat loss, overharvesting, new pathogens.
  2. Stochastic Extinctions
    • Result from random environmental fluctuations affecting small populations.

  • Extinction Vortex

  • A cycle where declining populations face increasing threats from environmental stochasticity, inbreeding, and others, leading to further decline.

  • Anthropogenic Drivers

  • Climate change, habitat destruction, pollution, invasive species, etc. contributing to declines in biodiversity.

  • Mass Extinctions

  • Defined as loss of 75% of species over a short duration.

  • Historical context indicates five such events and the potential for a sixth due to current rates.

  • IUCN Red List

  • Categories include extinct, critically endangered, vulnerable, etc., aiding species conservation efforts.

  • Current Extinction Crisis

  • High extinction rates in Australia, particularly among mammals, driven by unique ecological pressures.

  • Over 1,700 species are at risk of extinction due to habitat loss, invasive species, and climate change.

  • Global Biodiversity Trends

  • Major declines observed in various taxonomic groups; significant proportions threatened with extinction (e.g., 40% of amphibians).

  • Human activity linked to recent extinctions—over 680 vertebrate species confirmed lost due to human impact.

  • Conclusion

  • Ongoing decline signifies urgent need for conservation efforts; frameworks like IUCN help guide actions against extinction.