Biodiversity loss is a critical issue in Earth's ecosystems. Human activities like habitat destruction, overexploitation, and pollution are major threats. Climate change and invasive species further exacerbate the problem, leading to species extinctions and ecosystem disruptions.

Measuring biodiversity involves assessing genetic, species, and ecosystem diversity. The loss of biodiversity has far-reaching consequences, impacting ecosystem services, stability, and resilience. Understanding these impacts is crucial for developing effective conservation strategies.

Threats to Biodiversity

Human-Induced Habitat Destruction

• Habitat loss occurs when natural environments are converted for human use (agriculture, urbanization, deforestation)
  • Leads to fragmentation, isolating populations and reducing genetic diversity
  • Disrupts migration patterns and breeding grounds
  • Example: Clearing rainforests for cattle ranching in the Amazon
• Overexploitation involves unsustainable harvesting of species from the wild
  • Includes overfishing, poaching, and illegal wildlife trade
  • Can cause population declines and extinctions (passenger pigeon, Atlantic cod)
• Pollution from human activities degrades habitats and harms organisms
  • Agricultural runoff (pesticides, fertilizers) contaminates water sources
  • Plastic pollution entangles marine life and is ingested by animals (sea turtles, seabirds)
  • Oil spills devastate coastal ecosystems and marine life (Deepwater Horizon spill)

Climate Change and Anthropogenic Impacts

• Climate change driven by anthropogenic greenhouse gas emissions alters habitats
  • Rising temperatures cause range shifts, phenological mismatches, and coral bleaching
  • Changing precipitation patterns lead to droughts, floods, and wildfires
  • Ocean acidification hinders shell formation in marine organisms (oysters, pteropods)
• Invasive species introduced by human activities outcompete native species
  • Lack natural predators in new environments, allowing unchecked population growth
  • Example: Burmese pythons in the Florida Everglades disrupt food webs
• Extinction occurs when the last individual of a species dies
  • Currently in the sixth mass extinction, primarily driven by human activities
  • Extinction is irreversible and leads to permanent loss of genetic diversity

Biodiversity Metrics

Measuring Biodiversity at Different Scales

• Biodiversity encompasses the variety of life at all levels of organization
  • Genetic diversity: Variation in genes within a species, enhancing adaptability
  • Species diversity: Number of different species in an ecosystem or region
  • Ecosystem diversity: Variety of habitats, communities, and ecological processes
• Species richness is the number of different species present in an area
  • Does not account for abundance or distribution of individuals within species
  • Example: A rainforest has higher species richness than a desert
• Evenness refers to how equally abundant the species are in an ecosystem
  • Low evenness indicates dominance by one or a few species (Antarctic penguin colonies)
  • High evenness suggests similar abundances across species (temperate grasslands)

Ecological Consequences

Importance of Biodiversity for Ecosystem Functioning

• Biodiversity underpins the provision of ecosystem services
  • Regulating services: Climate regulation, water purification, pollination
  • Provisioning services: Food, timber, medicinal resources
  • Cultural services: Recreation, aesthetic value, spiritual significance
• Greater biodiversity often enhances ecosystem stability and resilience
  • Functional redundancy: Multiple species performing similar roles buffers against disturbances
  • Example: Diverse grasslands are more resistant to drought than monocultures
• Keystone species have disproportionately large effects on ecosystem structure and function
  • Their removal can trigger trophic cascades, altering community composition
  • Example: Sea otters maintain kelp forests by controlling sea urchin populations
• Trophic cascades occur when changes at one trophic level affect multiple other levels
  • Wolves in Yellowstone: Reintroduction reduced elk populations, allowing aspen and willow recovery, benefiting beavers and songbirds
  • Loss of apex predators can lead to overgrazing, habitat degradation, and species declines