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The earth has always experienced change. In the past, severe climatic
changes and physical events such as meteorite collisions were responsible
for periodic large-scale transformations of the environment and five global
mass extinctions. Today, the planet's ecosystems are again being rapidly
altered and undergoing a massive loss of biodiversity that has been called
the Sixth Extinction. But this time, the changes are caused solely by human
activity.
Even in prehistory, humans extinguished many other species as they spread
across the world. For example, the saber-toothed tiger and mastodon were
just some of the organisms to disappear soon after humans first reached the
Americas. But with the explosion of the human population following the
invention of agriculture around 10,000 years ago, our demand for and impact
upon biological resources dramatically intensified.
The development of increasingly sophisticated technologies has only
accelerated our ability to disrupt, deplete, and destroy natural systems.
By converting and polluting forests, prairies, and wetlands; overexploiting
wildlife and fisheries; and transporting alien species across the globe,
humanity is greatly altering the surface of the planet, causing the
dramatic decline of species in today's "Biodiversity Crisis."
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