Once humans gained control over their food supplies, they were no longer limited by their environment's natural productivity. What costs have come along with this tremendous benefit? 

It's not surprising that the larger the world's population grows, the more fresh water we consume. But what is surprising is just how much of this precious commodity we've depleted in recent years.

Did you know that the world's deserts keep expanding each year? Or that islands have the highest animal extinction rate—75 percent? Take a closer look at the major habitats found on Earth.

Did you know only 10 percent of people in rural Madagascar have access to safe drinking water? Or that Africa has the worst infant mortality rate? Take a global look at important health issues. 

Today, at least 16 million hectares of forests are lost each year to timber harvesting and the conversion of forests to farmland. See the dramatic decline of the Earth's original forest cover.

Larger and larger catches of fish may be good for commercial fishing operations, but they're not good for the world. Find out which regions and species are at the greatest risk.

It's not just humans who have jetted to remote regions of the world. For better or worse, international commerce and air travel have helped the global exchange of species and the spread of disease.

Would you believe that the U.S., Europe, the former Soviet Union, and Asia consume more than 85 percent of the world's energy? Take an eye-opening look at consumption.