Recyclers in Nature

Recycling something means using it again, especially by breaking it down and making something else out of it. Most students know that humans recycle cans, bottles, newspapers, and other items. However, there are also recyclers in nature.

Nature's recyclers are living beings that break down other living or formerly living things to smaller materials that are deposited in soil, where the materials are used again (recycled) by plants.

Soil and Humus
Soil is the loose upper layer of earth in which plants can grow. The surface layer, called topsoil, has some black or dark brown areas called humus.

Humus is material resulting from the breaking down of organic matter, that is, the remains of living organisms, such as plants and animals. It consists mainly of carbon, with smaller amounts of nitrogen, phosphorous, and sulfur. As the organic matter breaks down, its parts are changed into forms that plants in the soil can use for growth.

Humus, which is soft and spongy, helps soil to hold water, and it typically has many spaces filled with life-giving oxygen. A good mixture of humus increases the ability of the soil to produce healthy plants.

Nature's creation of humus-rich topsoil is slow. One inch of topsoil may take between 250 and 2,000 years to accumulate.

Decomposition
The process of breaking down organic matter is called decomposition. The word decompose means "break down," "rot," "decay," or "disintegrate." Moldy bread, rotten fruit, and decayed logs are examples of decomposition.

Decomposition causes both chemical changes and physical changes. Chemically, it takes some nutrients away from organic matter and deposits other forms of nutrients into the humus portions of the soil. Physically, decomposition changes the appearance, such as the shape and texture, of the organic matter and adds new layers of material to the soil.

Decomposition is carried out by a wide variety of living beings--nature's recyclers.

Recyclers
Fungi (singular, fungus) are microscopic organisms that cannot make their own food, as plants do, so they take nutrients from other organisms, living or dead. Fungi include mushrooms, mildews, and yeasts.

Bacteria (singular, bacterium) are microscopic, single-celled organisms that, like fungi, absorb nutrients from other organisms. They play an important role in recycling carbon, nitrogen, sulfur, and other elements necessary for life. Some bacteria decompose dead organisms and animal wastes into simpler chemical compounds. Others convert chemical elements into forms that plants and animals use for growth. For example, some bacteria change nitrogen in the air and soil into nitrogen compounds that plants use.

Animals of various kinds and sizes contribute to nature's recycling process. Familiar examples include earthworms and sow bugs (also called wood lice). They digest organic matter and then deposit the decomposed material into soil as waste. Earthworms also dig little tunnels that provide the soil with nutrients from air, such as oxygen.

Many insects, including termites and some beetles, feed on, and therefore help break down, fallen logs and other plant tissues. Some insects lay their eggs in the wood of a fallen log or in a pile of leaves. When the larvae hatch, they feed on the dead plant material. The recycling process goes a step further when the insects are eaten by birds or other animals that deposit their waste into the soil.

A fallen log, in fact, is a good place to observe many of nature's recyclers as they decompose the wood: algae, ants, centipedes, earthworms, ferns, lichens, mosses, mushrooms, slugs, sow bugs, termites, and others.

Cows exemplify larger recyclers in nature. Their digestive systems contain bacteria that convert food (grasses and grains) into manure, a nutrient-rich waste product.

From microscopic organisms to large animals, nature's recyclers constantly reuse organic matter to replenish life-giving nutrients in the soil.
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Encyclopaedia Britannica Ready Reference 2004. CD-ROM. Encyclopaedia Britannica 2004.

Slattery, Britt Eckhardt. Wow! The Wonders of Wetlands. Michaels, Maryland: Environmental Concern, 1991.