Carbon Cycle: How Decomposition Benefits Ecosystems
Eventually, all living things die. Our ecosystems need the death to occur in order to breathe new life into something else. This cycle is called the Carbon Cycle, and you and I are part of it.
To understand how decomposition benefits our ecosystems we must first understand the process of death. I’ll try to lessen the gore-factor, but death isn’t pretty. If you’re at all squeamish, you may want to skip to the end.
The Process of Death
When the death process begins, we quickly lose the ability to cough or swallow. This prevents our lungs from releasing mucus and leads to the “death rattle.” Anyone who’s heard it can attest to its unmistakable, unforgettable sound.
Within minutes after our heart stops beating, our muscles relax – called primary flaccidity – and blood begins to drop, settling in the lower-most parts of the body. Around 8-12 hours later, the skin in those areas become discolored by postmortem stain aka livor mortis.
With no blood flow, no oxygen being circulated, and the livor no longer producing adenosine triphosphate (ATP), cell death occurs. Those flaccid muscles 2-6 hours earlier will now begin to stiffen – aka rigor mortis (pronounced rye-gore) – first in the eyelids, jaw, and neck. The vocal chords can even release a squeal or moan as they stiffen. Imagine being alone in the morgue when that happens? Or worse, alone in a darkened forest?
After 4-8 hours rigor travels to the limb joints and extremities and fixes in the organs in about 12 hours. Rigor releases in reverse order and can be absent in as little as 12 hours, depending on various factors.
The body then cools or rises to match its environment – a process called algor mortis – and this stage also depends of various factors, including age, clothing, weight, fever, drugs, atmospheric temperatures, etc. The body also changes color – a process called palor mortis. For an in-depth look at the four stages of mortis see this post.
Autolysis and putrefaction occur in tandem.
The body purges itself of bodily fluid. Organs with the largest blood supply liquefy, mix with blood, and seep out any and all orifices. Some mistake this fluid for blood due to its reddish-brown color. As the fluids build, pressure breaks down the abdominal wall, flooding the body.
For writers, if your victim has been out in the elements for a number of days and reaches this point, the skin could take on a bloated, greenish-black appearance. Check this post for more info.
Decomposition is caused by bacteria and insects breaking apart the body. Many factors determine the rate of decomposition. There is, however, a basic guide to the effect of the environment on decomposition. Casper’s Law states, if all other factors are equal, a body exposed to air decomposes twice as fast as one submerged in water and eight times as fast as one buried in soil. However, soil acidity greatly affects bone preservation. High acidity soils with a PH less than 5.3 will rapidly decompose bone. Whereas neutral soil with a PH of 7 or more can allow a skeleton to remain in remarkably good condition for centuries.
For bodies in water, during the decomposition stage skin can deglove. The underlying tissue breaks down, muscles and tendons release, and the skin has the ability to slip off the body in sheets. Hands and feet can dislodge and float away. I could go on and on about how bodies react in water (I kept the Grafton County Medical Examiner on the phone for over an hour), but we’ll save those juicy tidbits for another time.
The same bacteria that leads to decomposition also emits a foul odor and causes the body to bloat in unimaginable ways. The abdomen, breasts, scrotum, and tongue swell while the eyes bulge from their sockets. If a pregnant woman dies, the build-up of gases can actually expel the fetus from the womb.
The rank stench worms its way into investigators’ clothes, hair, mouth, nostrils, even their skin reeks of the stench of death. In CLEAVED, Niko mentions the hamper Sage stuck out in the mudroom – marked “Death Laundry” – to help keep the wretched stank from seeping into their home.
How Death Relates to the Carbon Cycle
Decomposition aids farmers, preserves forests, and even helps to make bio-fuels. Hence why so many scientists are interested in decay, including how climate change and pollution affects it.
“Life would end without rot,” observes Knute Nadelhoffer, an ecologist at the University of Michigan. “Decomposition releases the chemicals that are critical for life.”
The most important element recycled by rot is 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 creatures capture the carbon to build new life. This process is called the carbon cycle.
“The carbon cycle really is about life and death,” says Melanie Mayes, a geologist and soils scientist at Oak Ridge National Laboratory in Tennessee.
The carbon cycle starts with plants. In the presence of sunlight, green plants combine carbon dioxide, extracted from the air, with water. Otherwise known as photosynthesis, which creates the simple sugar glucose made from carbon, oxygen, and hydrogen.
Plants use glucose and other sugars to grow and fuel all of their activities, from breathing to growth to reproduction. When plants die, carbon and other nutrients stay in their fibers. Stems, roots, wood, bark and leaves all contain these fibers.
“Think of a leaf like a piece of cloth,” says Jeff Blanchard, a biologist who works at the University of Massachusetts (UMass). “Cloth is woven with different threads, and each thread is made of fibers spun together.”
The walls of each plant cell contain fibers made up of carbon, hydrogen, and oxygen. These fibers are called hemicellulose, cellulose, and lignin. Hemicellulose is softest. Cellulose is sturdier. Lignin is the toughest of all.
When a plant dies, microbes and fungi breakdown these fibers by releasing enzymes. Enzymes are molecules that speed up chemical reactions. As the plant dies these enzymes help breaks the chemical bonds that hold the fibers’ molecules together. Snipping those bonds releases the nutrients, which include glucose.
Still with me? Okay, cool.
Cellulose is basically glucose rings that are attached to one another. During decomposition, enzymes attach to the cellulose and break the bond between the two rings. The isolated glucose molecule can then be absorbed as food, and the new organism uses that sugar for growth and reproduction. Along the way it releases carbon dioxide as waste. Which sends carbon into the air for reuse, and the carbon cycle continues.
Carbon isn’t the only element that gets recycled this way. Decomposition or rot also releases nitrogen, phosphorus, and about two dozen other nutrients.
When a human body decomposes in the elements it releases its fluids into the earth. This fluid is rich in nutrients, but it’s also rich in nitrogen. The nitrogen initially kills the plant life around the body, but one year later that same soil becomes especially fertile. The ecosystems depend on harvesting nutrients to create new life. Hence why so many people are now opting for environmentally-safe means of burial to help do their part to save our planet.
Have you seen some of the options? My buddy Garry wrote a fascinating post about it. Is there one you’d like your loved ones to consider?
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Sue Coletta
Sue Coletta is an award-winning crime writer and an active member of Mystery Writers of America, Sisters in Crime, and International Thriller Writers. Feedspot and Expertido.org named her Murder Blog as “Best 100 Crime Blogs on the Net.” She also blogs on the Kill Zone (Writer's Digest "101 Best Websites for Writers"), Writers Helping Writers, and StoryEmpire. Sue lives with her husband in the Lakes Region of New Hampshire. Her backlist includes psychological thrillers, the Mayhem Series (books 1-3) and Grafton County Series, and true crime/narrative nonfiction. Now, she exclusively writes eco-thrillers, Mayhem Series (books 4-9 and continuing). Sue's appeared on the Emmy award-winning true crime series, Storm of Suspicion, and three episodes of A Time to Kill on Investigation Discovery. When she's not writing, she loves spending time with her murder of crows, who live free but come when called by name. And nature feeds her soul.
22 Comments
Steven Ramirez
Though I am struggling to swallow my gorge, this is a fantastic post, Sue. Now, I can finally face gutting that fish.
Sue Coletta
Hahahaha. Oh, I could never gut a fish. Gross. 😉
Frances
Sue, Graphic but excellent post. Thank you.
Sue Coletta
Thank you, Frances. Yeah, sorry about the mental images. I’d hoped readers would find the subject of death more fascinating than gory.
David Hermens
I am amazed at how fast insets like blow flies are attacked to a dead body. I have read that it can start within minutes of death.
Sue Coletta
Minutes might be a stretch, David. More like hours. ‘Course, location would play a roll. In the heat of Louisiana, I’m sure they find the corpse much faster than, say, New England in the winter. A cool tidbit is, if a body is indoors, it takes blowflies 3 full days to get inside. Always 3 days. Never 2, never 4. Fascinating, right?
patriciaruthsusan
Great post, Sue. My dad was a fireman so was used to death. After being called by a neighbor of a relative, he was the one to find the body of the man who died from natural causes. He called the police and asked why rigor mortis had not set in. The policeman told him the body was past the first stages of rigor and was back to being relaxed. —- Suzanne
Sue Coletta
That couldn’t be easy for your father, Suzanne. Bodies react differently in fire. Although they still go through rigor mortis, which sets and releases, the body also goes into a pugilistic pose where the arms curl inward as if protecting itself from the flames. At the body farm they tested this theory with severed limbs. Sure enough, even when separated from the body the extremities reacted in the same way.
Garry Rodgers
Hey Sue – You keep coming up with great & gruesome stuff. Makes me wonder what’s coming next 🙂 Couple points for others from an old cop & coroner. The smell of putrefaction is overpowering, even for someone “used” to it. I made the early mistake of wearing a leather jacket to a “stinker” scene. Particulates invaded the jacket’s pores and stayed there. I had to throw it out.
You’ve also got the pH scale right for decomp. Low # pH acidic conditions break down organics faster than high # pH alkaline spots. Many writers buy into the old “using lime and lye” to quickly dispose of bodies but this is a myth.
In old days, lime (which is very alkaline – high pH – was used to slow decomp, stop insect invasion and control smells. It actually raised the pH level and retarded decomp which works against sinister hiding. So having the bad guy douse the corpse in lime/lye just helps forensic archaeology finding the truth.
Sue Coletta
Wow, Garry. Love when you add your experience. Having the bad guy add lime/lye to the corpse might be a great way for the investigator to gain the upper hand. It’d sure make for a fascinating and unique scene. I may have to use that tidbit. 🙂
Denise Hendrickson
Extremely interesting post. I am actually impressed with myself that I knew some of this stuff. LOL Disturbing info. on vocal chords sounds though. To be alone and hear that would not be fun at all.
Sue Coletta
Ha! Right? Someday I’ve got to write a scene where the killer hears the corpse moan. It’s too juicy of a detail to miss!
When the mechanics of death sound all-too familiar, you know you’ve been hanging around crime writers and/or cops for too long. 😉
Mae Clair
Very interesting, Sue. I’ve had to do a lot of snooping around on burials for my latest WIP, so I found this post timely. I also see there is now an interest in simple pine box burials and in conservation cemeteries.
Thanks, too, for the nugget of information on PH levels in soil and how it effects bones. My WIP deals with some very old remains so it was great to learn bones can last for centuries.
Sue Coletta
Thanks, Mae. Always happy to help. I’m working on story that deals with conservation, so I’ll be sharing more research as I go along.
Conservation cemeteries are now more important than ever. We’re running out of space to bury our dead. And yes! Skeletons in the right soil can last for centuries. Just be sure to bury the body deep enough so scavengers don’t destroy the remains. Vultures can strip a corpse in a matter of hours. Also, depending on where your story takes place, some species of animals thrive on eating bone. Red deer, camels, giraffes, wildebeest, antelopes, tortoises, grizzly bears, vultures, hyenas, etc., and there’s one type of eagle that relies entirely on bone.
E. Michael Helms
Highly interesting & informative post. Thanks, Sue! 🙂
–Michael
Sue Coletta
Thanks, Michael! Glad you enjoyed it. 🙂
CS Boyack
Interesting stuff today. I wonder if the term lignin is somehow related to lignite coal.
Sue Coletta
Hmm, from what I gather lignite coal is soft, right? So, I doubt the words are related. ‘Course, I could be wrong. It’s happened once or twice before. 😉
Margot Kinberg
This is absolutely fascinating, Sue – thank you! And it’s a great example of nature’s interconnectedness. There really is a system to how it all fits together.
Sue Coletta
There certainly is, Margot. No one makes this more clear than Sir David Attenborough, albeit in a different context. 😉
Michele Carlon
I’m a physician, but they don’t teach us about decomposition I. School. As always, I appreciate your fascinating articles. I always learn something.
Sue Coletta
Interesting, Michele. I would think decomposition would be an important subject for a physician. Especially cell death i.e. gangrene. Perhaps that’s an area physicians learn on the job. Thanks for your kind words. Wishing you an amazing day!