Hydrosphere: Freshwater Sytems and Pollution (Our Fragile Planet)Earth is the water planet, but only a tiny amount of the planet's water is fresh and usable, and water pollution has become a monumental dilemma as we enter the 21st century. Though developed nations now regulate some pollutants and as a result their waterways are cleaner, new chemicals are increasingly being released into the environment, resulting in a toxic soup that may be causing cancers, development problems, and other concerns in people and wildlife.
Geosphere: The Land and Its Uses (Our Fragile Planet)People exploit the land for desired resources, such as oil, minerals, or timber, or they convert vast expanses of natural terrain to landscapes that better meet their needs: Forests become tree plantations, wilderness is converted to agricultural land, and even farms are paved over to make cities. Already about half the ice-free land area has been converted for human purposes, and that number is growing rapidly.
Climate: Causes and Effects of Climate Change (Our Fragile Planet)
Though climate change is normal in Earth's history, global warming has raised average temperatures to their highest in two millennia, resulting in melting ice caps, shorter winters, changes in the seasonal behaviors of animals, and more extreme weather. And though greenhouse gases are essential for keeping the planet's temperatures comfortable, fossil fuel burning and other human activities are increasing greenhouse gas levels and causing temperatures to rise.
