Why Is Topsoil Considered a Non-Renewable Resource?
- A renewable resource must be able to sustainably reproduce at a rate equal to or greater than it is consumed or destroyed. The fact that a particular resource can naturally build up over time does not mean that it is renewable. If it is depleted faster than it can replenish, then it is non-renewable. It will eventually disappear without intervention.
- Topsoil is the outer layer of fertile, nutrient-rich soil that is capable of sustaining healthy plant life. Globally, it averages out as the top three feet of soil. It sits atop the infertile subsoil, which is made up of clay and hard minerals like iron. Topsoil grows as dead plant and animal matter is broken down. This natural decomposition process creates topsoil at a very slow rate, taking about five hundred years to make just an inch or two.
- Poor agricultural planning can devastate topsoil over time.tilled field image by Niki from Fotolia.com
The main causes of soil erosion are wind and water, which sweep soil away over time. Under normal conditions, erosion typically happens at the same rate that topsoil regenerates. Some human actions, many of them agricultural, accelerate erosion. For example, annually planting a single crop on large fields depletes the soil of nutrients, while tilling soil strips out root systems, leaving topsoil loose and easily swept away. Topsoil relies on strong root systems to fight erosion. Shallow topsoil means less room for roots to take hold, and less nutrients to nourish plants. In turn, weaker plants secure the topsoil poorly, which erodes more quickly. This cycle eventually ruins the soil. - Many people simply assume that soil is a renewable resource, as soil scientist John Reganold points out in the 2008 article, "The Lowdown on Topsoil: It's Disappearing." However, scientists have found much evidence to the contrary. In the same article, geologist David Montgomery reports that soil erosion annually destroys roughly one percent of the earth's topsoil, often due to agricultural practices, and the National Academy of Sciences calculates that in the U.S., agricultural soil erosion occurs 10 times faster than topsoil regenerates.
- There are several ways to help. One is to buy organic, sustainably farmed produce. Doing so monetarily supports sustainable farming methods like crop rotation, which maintain strong topsoil. Another solution is to compost. According to Eartheasy.com, typically up to 30 percent of kitchen waste is compostable, speeding the decomposition process to create new soil. You can also spread the word. Many people incorrectly believe that topsoil is renewable, but knowing the truth is the first step toward solving the problem.
