California State University Long Beach 

Reduced biodiversity

• Biodiversity = number of species present at any time
• Currently
• 1 to 1.4 million species catalogued
• Probably 5 to 100 million total on Earth

 
• Biodiversity depends on
• Balance between:
• The rate of evolution
• The rate of extinction

 
• Natural change
• Past average life span of species: 100,000 to 1 million years
• 10 to 100 new species estimated to evolve each year
• Species lost due to inability to adapt to changing environmental conditions
• Sudden, local natural disasters
• Gradual change

Modern changes in biodiversity

• Modern extinction rates have increased dramatically along with human population 
  due to:
• Habitat loss (deforestation) because of need for:
• Living space
• Fuel wood
• Commercial lumber
• Agriculture (crops and pasture)
• Elimination of pest species
• Overhunting
• Introduction of exotic species to ecosystems
• Poisoning by pollution

 
• Estimated extinction rate for plants and animals
• 24 to 400 species per day (>8000 per year!)
• Up to 100 -10,000 times faster than new species evolve!

 
• Key areas at risk
• Tropical rain forests
• Probably contain over 1/2 of all species on Earth
• Being deforested at ~100,000 km2 per year
• Coral reefs
• Increased temperature kills living coral
• Damage due to harvesting sea
• Food, jewelry, shells

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