Topsoil is the uppermost surface layer of soil. It is usually never more than 12 inches deep, typically six to ten inches. Topsoil not only contains nutrients and minerals but bacteria which is essential for healthy root and plant growth. Since it can take hundreds of years to be develop adequately, yet be washed away into the rivers and oceans in one rain storm, topsoil is one of our most valuable natural resources and we must continue steps in conservation to preserve it.

What is Soil Erosion and how can we help prevent it?

LEARN MORE about worldwide land use.

Desertification is the term used when fertile land turns into a desert and is a serious problem because the loss of productive land can lead to famine. During the last two to three thousand years, many deserts have formed naturally as Earth's climate has changed from cool and moist to warm and dry. More recently, human activities have caused deserts to expand. The expansion happens on the outskirts of a desert and is usually caused by over grazing by livestock, to the point where all plant life is destroyed. Without the protective cover of plant life, wind and water increase soil erosion. A few other human-related activities responsible for desertification are mining, improper farming methods, and destruction of trees.

LEARN MORE about deserts and other plant ecosystems.

Energy is probably the one most important resource available to us on Earth, used directly or indirectly, we cannot live without it. The supply is measured by the amount of usable energy available to people for

Fossil fuels such as coal, petroleum and natural gas provide over 80% of the energy produced commercially. Fossil fuels are named such because they are developed from the fossilized remains of prehistoric plants.