DOES THE PLANET HAVE ITS OWN RECYCLING SYSTEMS?

The saying that there is nothing new under the Sun is strangely true. The stuff that makes up everything on Earth —animals, plants, rocks, water — cannot be destroyed, although it can be changed from one form to another. Living things are almost entirely made up of six elements: carbon, oxygen, hydrogen, nitrogen, phosphorous and sulphur. When a plant or animal dies, it decomposes. Gradually, its body breaks down, and the elements it was made of go back into the soil or water. These elements in time are taken up by new plants, which in turn are eaten by animals. This cycle of elements being released and re-used can take millions of years, but it is quite likely that within your body there are chemicals that were once part of a prehistoric plant — or even a dinosaur!

Eventually, all living things die. And except in very rare cases, all of those dead things will rot. But that’s not the end of it. What rots will wind up becoming part of something else. This is how nature recycles. Just as death marks the end of an old life, the decay and decomposition that soon follow provide material for new life. “Decomposition breaks apart dead bodies,” explains Anne Pringle. She’s a biologist at Harvard University in Cambridge, Mass.

When any organism dies, fungi and bacteria get to work breaking it down. Put another way, they decompose things. (It’s the mirror image of composing, where something is created.) Some decomposers live in leaves or hang out in the guts of dead animals. These fungi and bacteria act like built-in destructors.

Soon, more decomposers will join them. Soil contains thousands of types of single-celled fungi and bacteria that take things apart. Mushrooms and other multi-celled fungi also can get into the act. So can insects, worms and other invertebrates. Yes, rotting can be yucky and disgusting. Still, it is vitally important. Decomposition aids farmers, preserves forest health and even helps make biofuels. That is why so many scientists are interested in decay, including how climate change and pollution may affect it.

Decomposition isn’t just the end of everything. It’s also the start. Without decay, none of us would exist. “Life would end without rot,” observes Knute Nadelhoffer. He’s an ecologist at the University of Michigan in Ann Arbor. “Decomposition releases the chemicals that are critical for life.” Decomposers mine them from the dead so that these recycled materials can feed the living.

The most important thing recycled by rot is the element carbon. This chemical element is the physical basis of all life on Earth. After death, decomposition releases carbon into the air, soil and water. Living things capture this liberated carbon to build new life. It’s all part of what scientists call the carbon cycle. The carbon cycle starts with plants. In the presence of sunlight, green plants combine carbon dioxide from the air with water. This process, called photosynthesis, creates the simple sugar glucose. It’s made of nothing more than the carbon, oxygen and hydrogen in those starting materials.