Biodiversity Loss and Species Extinction Extinction vs Extirpation

Biodiversity Loss and Species Extinction

Extinction vs. Extirpation • Extinction occurs when the last member of a species dies and the species ceases to exist. • Extirpation is the extinction of a particular population from a given area, but not the entire species globally. (ex. Tiger) • Extirpation often leads to extinction

Extinction is “natural” • Imagine a world today with dinosaurs, trilobites, ammonites, etc. – there would be no room for us! • 99% of the species that ever lived are already extinct. Only about 1% of the species today are those that have ever existed. • Background rate of extinction: rate of extinctions that occurred before humans. Approximately one species every 500 -1, 000 years

Mass Extinction • 5 times in the last 440 million years, the extinction rate has been much higher than the background rate.

A Sixth Mass Extinction? • Humans have set the stage for a 6 th mass extinction based on the current extinction rate – 30, 000 species face extinction and ~1100 have gone extinct in 400 years

• Poaching is a controversial issue in African and Asian nations, as the products (tusks, skins, etc. ) are the livelihood of some of the poor in these countries. However, poaching also leads to extirpation and sometimes extinction of those species. Compare and contrast the positive and negative aspects of poaching and come to a conclusion as to whether poaching should continue or not.

5 Reasons for Species Loss: HIPPO • Habitat alteration • Invasive Species • Pollution • Population Growth • Overexploitation

Habitat Alteration • Agriculture removes food, shelter and other resources for wildlife • Hydroelectric power alters water conditions • Urbanization and suburban sprawl • Global climate changes (global warming) • Primary source of population declines • Can benefit a few species (pigeons)

Invasive Species • Non-native species that spreads widely and rapidly, out competing the natural species of that area • Transported by ships, planes, animal trade, seeds, human immigrants bringing their native plants/animals, purposely for aesthetics, economic reasons • Without predators and with unlimited resources, species flourish and take over • ex. Brown tree snake

Brown Tree Snake as an Invasive Species • Transported in cargo on ships and planes during WWII • Native to Solomon Islands, New Guinea, Australia • Invasive in Guam • Have destroyed the populations of 12 native birds to Guam

Pollution • Air pollution degrades forest ecosystems • Water pollution affects fish and amphibians • Agricultural runoff can harm terrestrial and aquatic species • Toxic chemicals and oil have greatly affected species in recent years

Population Growth • More people mean more habitat alteration, more pollution, more overexploitation, more invasive species, more resource consumption, etc. • Ultimate reason behind the threats to biodiversity

Overexploitation • Overharvesting of species and overconsumption of resources • Poaching in the grasslands of Africa and Asia have greatly depleted the species of animals – tigers, antelope, elephants • Consumption of paper products leads to increased need for logging, decreasing number of trees and in the long run, causing global warming (CO 2 increase)