Biodiversity Crisis Notes

Introduction to the Biodiversity Crisis

• Global Challenge #1: The biodiversity crisis as presented by A/Prof Steve Salisbury from the School of the Environment.
• Key topics include:
  • Definition and importance of biodiversity.
  • Relationship between biodiversity and evolution.
  • Historical perspective on biodiversity in Australia.
  • Current state of biodiversity and potential mass extinction events.
  • Indigenous perspectives and the role of biological taxonomy.
  • Conservation challenges and strategies.

Understanding Biodiversity

• Definition: Biodiversity = Biological + Diversity
  • Genetic Diversity: Variation in genetic composition.
  • Species Diversity: Variety of species within an ecosystem.
  • Ecosystem Diversity: Variety of ecosystems in a given place.
• Importance of biodiversity as a measure of health of ecosystems and a buffer against environmental changes.

Current State of Biodiversity

• Nearly all groups of animals and plants are in decline globally since 1970; approximately 1 million species are currently at risk of extinction (out of 8 million known species).
• Extinction rates are around $100$ times faster than natural evolutionary processes.
  • Specific extinction risks:
  • 15 ext{%} of bird species threatened.
  • 30 ext{%} of frog species threatened.
  • 32 ext{%} of pelagic sharks and rays threatened.
  • 25 ext{%} of mammal species threatened.
  • Almost 50 ext{%} of primates under threat.

Iconic Species and Extinction Events

• Vertebrates (fishes, amphibians, reptiles, birds, and mammals) are often highlighted in discussions of biodiversity loss due to their visibility and ecological roles.
• Example of an extinction event: The last male Northern White Rhino died in 2018, emphasizing the urgency of the crisis.

Trophic Cascades

• Major species can cause significant ecological influence due to their roles in food webs, showcasing the term "extinction cascade" where the extinction of one species triggers the loss of others through food web dynamics.
  • Example: Steller’s Sea Cow extinction linked to other species' losses.

Rates of Extinction in Australia

• Since European invasion (past 230 years), Australia has seen numerous extinctions among various species, including:
  • $38$ plant species.
  • $34$ mammals (e.g., Thylacine).
  • $10$ invertebrates.
  • $9$ birds.
  • $4$ frogs.
  • $3$ reptiles and $1$ fish.

IUCN Red List

• The IUCN (International Union for Conservation of Nature) categorizes species based on their extinction risk:
  • Categories: Extinct, Critically Endangered, Endangered, Vulnerable, Near Threatened, Least Concern.

Case Studies: Amphibians and Insects

• Amphibians:
  • Of approximately $6,400$ described species, 30 ext{%} face extinction due to habitat loss, exploitation, and emerging diseases.
  • Significant decline observed in Australian frogs, with $59$ species threatened.
• Insects:
  • Estimated $900,000$ described species, facing threats from habitat loss, pollution, and climate change.
  • Long-term studies indicate a 76 ext{%} decline in insect biomass in Germany.

Global Threats to Biodiversity

• Major threats include:
  • Habitat loss, degradation, and fragmentation.
  • Over-exploitation of resources, especially fisheries.
  • Pollution from plastics and chemicals.
  • Invasive species and emerging diseases.
  • Climate change impacting habitat and species distribution.

Conclusion: The 6th Mass Extinction?

• Current biodiversity loss is compared to previous mass extinctions, termed the 6th mass extinction, primarily driven by human activity.
• Key to address the crisis includes understanding local examples and global factors driving species decline, aimed at conservation efforts.