7.1 Extinction Rates and the Extinction Crisis

Extinction rates are skyrocketing, way beyond natural levels. We're in the middle of a crisis, with species disappearing faster than ever. It's not just about losing cute animals – it's messing up entire ecosystems and could seriously impact our lives.

Humans are the main culprits here. We're destroying habitats, polluting, overfishing, and changing the climate. It's a perfect storm for wiping out species. The consequences? Unstable ecosystems, loss of important services nature provides, and potential ripple effects we can't even predict yet.

Extinction: Background vs Mass

Defining Extinction and Its Types

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  Earth's five mass extinction events View original

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Top images from around the web for Defining Extinction and Its Types

• 

  Earth's five mass extinction events View original

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• 

  Big 5 Mass Extinctions Poster by BudCharles on DeviantArt View original

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• 

  Charting Earth’s (Many) Mass Extinctions — Blog of the Long Now View original

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• 

  Earth's five mass extinction events View original

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• 

  Big 5 Mass Extinctions Poster by BudCharles on DeviantArt View original

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• Extinction signifies complete, permanent loss of a species from Earth without surviving individuals or viable populations
• Background extinction represents natural, ongoing species loss over geological time scales
  • Caused by environmental changes or competition
  • Estimated rate of 1-5 species per year per million species
• Mass extinction events exhibit significantly increased extinction rates
  • Far exceed background levels
  • Affect large proportion of species across diverse taxonomic groups
  • Result in loss of over 75% of species within relatively short time frame
  • Earth experienced five major mass extinction events in geological history

Current Extinction Crisis

• Often referred to as the sixth mass extinction
• Characterized by extinction rates 100 to 1000 times higher than background levels
• Driven by human activities and their far-reaching impacts on global ecosystems
• Poses significant threats to biodiversity and ecosystem functioning

Drivers of Extinction Crisis

Habitat Alteration and Loss

• Habitat loss and fragmentation lead causes of species extinctions
  • Primarily due to human activities (deforestation, urbanization, agricultural expansion)
• Climate change alters ecosystems and species distributions
  • Causes mismatches in ecological relationships
  • Pushes species beyond physiological tolerances
• Land-use changes reduce available habitat and fragment remaining populations
  • Agricultural intensification
  • Urbanization

Resource Exploitation and Pollution

• Overexploitation of natural resources directly threatens many species
  • Particularly impacts species with high economic value or slow reproductive rates
  • Examples include overfishing, hunting, and poaching
• Pollution degrades habitats and impacts species health and survival
  • Chemical contaminants
  • Plastic waste
  • Excess nutrients

Biological Threats

• Invasive species introductions disrupt native ecosystems
  • Outcompete or prey upon native species
  • Alter ecological processes
• Emerging infectious diseases cause rapid population declines and extinctions
  • Often exacerbated by human activities and global trade
  • Particularly affects vulnerable or isolated populations

Human Impact on Extinction Rates

Population Growth and Resource Consumption

• Human population growth drives unprecedented rates of habitat destruction
• Increasing per capita resource consumption leads to resource depletion
• Technological advancements amplify human impacts on ecosystems
  • Enable large-scale habitat modifications
  • Allow more efficient resource extraction

Globalization and Climate Change

• Globalization and international trade facilitate spread of invasive species and pathogens
  • Increases extinction risks for native species
• Anthropogenic climate change alters species distributions, phenology, and interactions
  • Exceeds many species' adaptive capacities
• Indirect effects of human activities create additional stressors for species
  • Ocean acidification
  • Desertification

Consequences of Species Extinction

Ecosystem Disruption and Instability

• Species extinctions disrupt food webs and trophic cascades
  • Can lead to secondary extinctions and altered ecosystem dynamics
• Loss of keystone species or ecosystem engineers has disproportionate effects
  • Potentially leads to regime shifts in ecosystem structure and function
• Reduced biodiversity decreases ecosystem resilience and stability
  • Makes ecosystems more vulnerable to disturbances and environmental changes

Impacts on Ecosystem Services

• Species extinctions impact crucial ecosystem services
  • Pollination
  • Seed dispersal
  • Nutrient cycling
• Consequences extend to human well-being and economic systems
• Loss of genetic diversity through extinctions reduces potential for future evolutionary adaptations
  • Limits options for biotechnology and medical research

Cultural and Cumulative Effects

• Extinctions of culturally significant species lead to loss of traditional knowledge and practices
  • Impacts human cultural diversity and indigenous communities
• Cumulative effects of multiple species extinctions can lead to ecosystem simplification
  • Potentially reduces capacity of ecosystems to provide essential services
  • May impact ability of ecosystems to support human populations