resources, like soils, plants and animals, minerals, and energy resources let’s keep in mind
about whether these are truly renewable or not.
For example, soils are often considered renewable, but because of erosionand mineral
depletion, this is not always the case (Figure25.16). Living things, like forests and fish,
are considered renewable because they can reproduce to replace individuals lost to human
consumption. However, overexploitation of these resources can lead to extinction.
Figure 25.16: Soil (Stagnogley) as a resource, showing a mixture of eroded rock, minerals,
ions, partially decomposed organic material, water, air, roots, fungi, animals, and microor-
ganisms, formed over thousands, possibly millions of years. ( 29 )
Also think about at what costs resources can be renewed. If something can be renewed,
but at great cost economically or ecologically, is that resource still considered renewable?
Perhaps a better way to put this is, does it make sense to renew a resource at great cost? If
you’re thinking that this discussion is leading up to energy resources, you would be right!
For example, energy resources derived from living things, such as ethanol, plant oils, and
methane, are considered renewable, but the environmental costs are not always adequately
considered. We will be discussing fossil fuels and alternative energy sources further in this
lesson.
Other renewable materials would includesustainable(at a rate which meets the needs of
the present without impairing future generations from meeting their needs) harvesting of
wood, cork, and bamboo, as well as sustainable harvesting of crops. Also, metals and other
minerals are sometimes considered renewable because they can be recycled, and are not
destroyed when they are used.