Life on Earth is in danger. Serious danger, and not from asteroids or aliens or anything else from a science fiction movie. Life on Earth is threatened by us, Homo sapiens, human beings.
Habitat destruction is rampant, wreaking havoc across the globe. Invasive species are spreading into new uncharted territory. Climate change is looming ominously over the planet like a college application deadline. Species are going extinct like it's going out of style. People, we have a crisis on our hands: a biodiversity crisis.
We hate to toot our own horns, but humans are really good at life. Not just the board game, but actually surviving, making babies, building cities, and driving cars. Our ever-increasing human population puts a lot of pressure on other species and their habitats. We all need to eat, drink, and take showers, or the world would be a much smellier place. The amount of land and water it takes to sustain a person's lifestyle is called his or her ecological footprint. Ecological footprints can be measured for individual people, cities, and countries. The ecological footprint of the United States is so large, it would take five Earths to support us if everyone in the world lived an American lifestyle. If you're reading this on Earth 5, you probably should have walked to work today.
Conservation biology is the study of the threats to life on Earth and the science of preserving biodiversity—protecting threatened species and helping recover endangered species. Conservation biologists use a variety of techniques to figure out which species are in trouble and what to do about it.