Being eaten by the invisible
Why Do Dead Things Rot?
Rotting is countless microbes eating what has died and returning the parts to the soil.
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Step 1 of 5
Dead tissue is a free meal.
A dead body is packed with energy and nutrients, and it is no longer defending itself. Bacteria and fungi move in immediately.
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Step 2 of 5
Fungi and bacteria do the dismantling.
They release enzymes onto the material, digesting it externally and absorbing the results. Rot is external digestion at a huge scale.
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Step 3 of 5
The smell is their waste gases.
Breaking down proteins releases sulphur and nitrogen compounds. Our strong disgust at those smells is a useful instinct.
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Step 4 of 5
Warmth and damp speed it up enormously.
Microbes need water and work faster when warm. Cold, dry or airless conditions can preserve tissue for thousands of years.
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Step 5 of 5
Without it, everything would stop.
Nutrients would stay locked in dead bodies and plants would run out. Decomposition is what puts carbon and nitrogen back into circulation.
Peat bogs are acidic and airless enough to stop decomposition, which is why they preserve bodies for thousands of years.
The short version
Rotting is microbes externally digesting dead matter, returning locked-up nutrients to the soil.
Try it yourself
Put one apple slice in a sealed bag and one in the freezer. After a week, compare — cold stops the microbes.
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