Materials which are capable of being recycled by the natural environment are called biodegradable. Animals can be eaten by other animals or smaller organisms such as bacteria. Plants are also used by organisms for food or become subject to decay. This is the way nature eliminates a staggering accumulation of dead plants and animals. Everything in the natural world is at some time an eater, and at other times eaten, and even occasionally both at once.
Imagine snacking on a delicious BLT while hosting a nasty case of athlete's foot. You are eating bacon, which means some poor piggy gave his all to lie in state on toasted bread slathered with mayonnaise, along with tomato and lettuce. The skin between your toes has become a cafeteria for tinea pedis, a parasitic fungus which finds you as delectable as you the BLT. The wheel of life continues to turn.
It took mankind to develop molecules which defy these natural processes. Most plastics and polymers are resistant to these processes, taking centuries instead of weeks to be broken down into their component elements. This creates the problem of where to stow these materials until they can be degraded by the environment. Landfills fill the bill in most cases, with recycling also making a major contribution to solving the problem.
With each person contributing to the amazing quantity of biodegradation resistant materials, manufacturers have started to work on producing materials which are more rapidly degraded by the environment. Increased efforts to promote recycling also has helped reduce the bulk of non biodegradable materials in landfills.
Most materials made of wood, plant fibers, and animal fibers degrade rapidly while others such as
glass and plastic bottles are, for all intents and purposes, immortal.
Landfills are not the most efficient engines for biodegradation as the material is often so compacted it is not readily exposed to oxygen, water, and micro organisms, all of which are necessary for efficient degradation into component materials.
For the foreseeable future our best hope lies with the 3 Rs of conservation: Re-use, renew, and recycle.
Sources:
http://www.chemheritage.org/EducationalServices/FACES/glossary/biodegra.htm
http://maps.grida.no/go/graphic/how-long-does-it-take-for-some-commonly-used-products-to-biodegrade