"Treat the earth well. It was not given to you by your parents, it was loaned to you by your children."
—Kenyan proverb

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."