Skip to content
NatureHQ

Ecologyphenomenon

Detritus

The food chain everyone learns handles a minority of what a forest actually produces.

Dead organic material — fallen leaves, wood, bodies, dung, and the fine fragments of all of them. In most forests it is not a by-product of the food web. It is where the majority of the energy actually goes.

Every food chain drawn for a classroom runs plant, herbivore, predator. Compile the actual production budgets and that pathway turns out to handle a minority of what plants make in most terrestrial systems — in forests, a small minority. The rest is never eaten alive. It falls, dies and enters detritus, and the organisms that live on it are almost entirely absent from the diagram. That is the case for treating this as the hidden half rather than as an appendix. The proportion is not universal, and the exception is instructive: in phytoplankton systems, where the plants are single cells with no structural tissue and a turnover of days, most production genuinely is grazed. What makes a forest different is wood and leaves built to resist being eaten — which works, and means the material has to be dealt with after death instead. Detritus behaves unlike the living half in one structural way that changes everything downstream. A rabbit population responds to being hunted; a pile of dead leaves does not. The resource arrives from outside, on a schedule set by the plants rather than by its consumers, and cannot decline because something is eating it. Food-web intuitions built on predator and prey do not transfer to a system with that asymmetry, which is why the detrital web has its own literature rather than a paragraph in the other one. It is worth separating two words that teaching materials blur. Decomposers — fungi and bacteria — break molecules apart chemically, releasing enzymes outside their bodies and absorbing what dissolves. Detritivores are animals that eat dead material and make the pieces smaller, and most of them digest surprisingly little of it: what they are often really eating is the microbial film growing on the surface. Their contribution is to shred, mix, transport and re-inoculate, which makes the chemical work faster. Two different jobs, done by organisms from different kingdoms, and the second mostly accelerates the first.

Early coverage · 43% complete · reviewed 2026-09-04

What this page covers

Detritus is produced by everything that lives and consumed by organisms from every kingdom. The pathway operates in soils, fresh water and the ocean, with the same structure and very different casts.

Often confused with: Soil, which detritus becomes part of rather than is; Waste, which implies something unused — this is where most of the energy goes; Decomposers, which are the organisms rather than the material

Quick facts

The hidden majority
In most forests, most plant production is never eaten alive
Not universal
In phytoplankton systems most production genuinely is grazed
Two different jobs
Decomposers break molecules; detritivores break lumps
A resource that cannot fight back
Dead leaves do not respond to being eaten — which changes the dynamics

Where the energy actually goes

Not up the chain everyone draws.

In most forests, the great majority of what plants make is never eaten by a herbivore. It dies, falls, and is dismantled — which is the pathway almost every food chain diagram omits.

Established

Specialists would state this without hedging. Multiple independent lines of evidence agree.

Compiled production budgets show the proportion of primary production consumed by herbivores varying systematically across ecosystem types, from a small minority in structurally complex, slow-turnover vegetation such as forests to a large majority in phytoplankton systems. The unconsumed remainder enters the detrital pathway.

Who this applies to
Terrestrial and aquatic plant communities; the grazed fraction differs enormously between them.
Studied in
Plantae
Why we rate it this way, and what the caveats are
EstablishedHigh confidence

A large compilation with a consistent pattern, though individual production budgets are hard to measure and methods differ between the studies compiled.

How far it can be extended

Compiled across forests, grasslands, marshes, seagrass, macroalgae and phytoplankton.

Caveats

  • Not universal: in phytoplankton systems most production genuinely is grazed, so this is a statement about forests rather than about life.
  • Production budgets are compiled from studies with differing methods, and within-type variation is large.

Still unanswered

  • How much the grazed fraction shifts under sustained herbivore change, which few systems have measured directly.

Last reviewed 2026-09-04

The evidence (2 studies)
How much production is eaten alive, by system type
SystemGrazed while aliveWhy
ForestA small minorityWood and tough leaves built to resist being eaten
GrasslandMore, but still often a minoritySofter tissue, but much still dies standing
Marsh and seagrassVariableStructural tissue, slow turnover
PhytoplanktonOften the majoritySingle cells, no structure, turnover in days

Diagram

How much of what plants make is eaten alive

The grazed share against the share that dies and enters detritus.

How much of what plants make is eaten aliveGrazedDies and enters detritusForestWood and defended leavesGrasslandSofter tissue; much still dies standingPhytoplanktonSingle cells, turnover in daysProportions are illustrative of the pattern, not measured values for a given site.
The same explanation in words

Three horizontal bars compare ecosystem types. In a forest a small marked segment is grazed and the great majority dies and enters detritus, because of wood and defended leaves. In grassland a larger share is grazed, though much still dies standing. In phytoplankton systems the grazed share is the majority, because single cells with no structural tissue turn over in days. A note records that the proportions illustrate the pattern rather than being measured values for any site.

The bottom row is the one that keeps the claim honest. "Detritus dominates" is a statement about forests, not about life — and the reason for the difference is exactly the thing that makes a tree a tree. Investing in wood and defended leaves means very little gets eaten, and it means almost all of that investment has to be dismantled after death instead.

Decomposers and detritivores are not the same thing

One breaks molecules. The other breaks lumps.

Decomposers — fungi and bacteria — break molecules apart chemically, outside their bodies. Detritivores are animals that eat dead material and make the pieces smaller, digesting little of it themselves.

Established

Specialists would state this without hedging. Multiple independent lines of evidence agree.

Decomposition proper is effected by microbial extracellular enzymes that depolymerise plant and animal macromolecules. Detritivorous animals fragment litter, alter its surface area and chemistry, transport it, and modify microbial communities through gut passage, but typically assimilate a modest fraction of the material ingested.

Who this applies to
The functional distinction as used across decomposition ecology.
Studied in
Fungi, Bacteria, Animalia
Why we rate it this way, and what the caveats are
EstablishedHigh confidence

A settled functional distinction with the mechanisms directly observed in both groups.

How far it can be extended

The distinction holds across terrestrial, freshwater and marine detrital systems.

Caveats

  • The boundary is functional rather than taxonomic, and some animals do substantial enzymatic breakdown themselves or via gut symbionts.
  • Many detritivores are really eating the microbes on the material rather than the material, which blurs the categories usefully rather than confusingly.

Still unanswered

  • How much of the acceleration detritivores produce is fragmentation and how much is changing which microbes are present.

Last reviewed 2026-09-04

The evidence (2 studies)
Who does what to a dead leaf
GroupWhat they doWhat they mostly are
DecomposersRelease enzymes outside the body; absorb what dissolvesFungi and bacteria
DetritivoresEat dead material, fragment it, mix and move itAnimals — woodlice, millipedes, worms, springtails
ScavengersConsume larger dead animal materialAnimals — vertebrates and large invertebrates

Diagram

What happens to a dead leaf

Five overlapping stages, and carbon going four different ways.

What happens to a dead leafFallsLitter reaches theLeachesSolubles wash out ColonisedFungi and bacteriaFragmentedAnimals shred and DispersedCO₂, biomass, soilThe stages overlap. Nothing waits for the one before it to finish.And the carbon does not go one place: some is respired, some becomes microbialbiomass, some dissolves and washes away, some ends up bound to soil minerals.
The same explanation in words

Five stages in sequence: the leaf falls; soluble compounds leach out within days; fungi and bacteria colonise it; animals fragment and mix it; and the material disperses. Notes beneath record that the stages overlap rather than waiting for one another, and that the carbon does not go to one place — some is respired to carbon dioxide, some becomes microbial biomass, some dissolves and washes away, and some ends up bound to soil minerals.

The detail that makes the distinction click is what a detritivore is actually digesting. Many get comparatively little from the leaf itself and a great deal from the microbial film covering it — they are grazing the decomposers rather than eating the litter. Which is why passing material through an animal so often speeds decomposition up: it arrives out the other end smaller, wetter, and freshly inoculated.

Related

  • Decomposition

    The chemical half, and why wood is so hard to eat

  • Scavenging

    The large-carcass end of the same pathway

  • Soil

    Where most of this ends up

A food web whose base cannot respond

And why that changes the dynamics.

A rabbit population responds to being eaten. A pile of dead leaves does not. That asymmetry — a resource delivered from outside, which cannot decline in response to its consumers — changes how the whole web behaves.

Well supported

Good evidence backs this, though some details remain open.

Detrital resources are supplied independently of their consumption, so the resource does not exhibit density-dependent response to consumer pressure. Detrital and grazing pathways are coupled within communities, and the coupling affects stability in ways dependent on web structure.

Who this applies to
Detrital food webs across terrestrial and aquatic systems.
Studied in
Animalia, Fungi, Bacteria
Why we rate it this way, and what the caveats are
Well supportedModerate confidence

The structural point is not in dispute. The stability consequences rest partly on models whose assumptions remain debated.

How far it can be extended

The structural asymmetry holds wherever detritus is the resource base.

Caveats

  • The independence is not absolute: consumers can affect future detrital supply by changing the plants that produce it.
  • Stability conclusions are model-dependent and less settled than the structural asymmetry.

Still unanswered

  • How strongly detrital and grazing pathways are coupled in real communities, which is rarely measured directly.

Last reviewed 2026-09-04

The evidence (2 studies)

Mix litter from different species and decomposition often runs faster or slower than the leaves alone would predict. Which direction is not reliably predictable, and that is the finding rather than a gap.

Well supported

Good evidence backs this, though some details remain open.

Litter mixture experiments frequently produce non-additive decomposition rates relative to single-species predictions, in both directions. Effects of decomposer diversity are generally weaker than those of substrate chemistry, and the mechanisms behind mixture effects remain unresolved.

Who this applies to
Terrestrial litter decomposition, chiefly in forest and grassland systems.
Studied in
Plantae, Fungi, Animalia
Why we rate it this way, and what the caveats are
Well supportedModerate confidence

The non-additivity is repeatedly observed; its direction and mechanism are not predictable, which limits what can be claimed.

How far it can be extended

Non-additive effects are reported across many mixture experiments.

Caveats

  • Most experiments run for months to a few years, which is short relative to the slow fraction of decomposition.
  • Publication of striking mixture effects may be favoured over null results.

Still unanswered

  • What determines whether a litter mixture decomposes faster or slower than its parts — genuinely unresolved.

Last reviewed 2026-09-04

The evidence (1 study)

The mixture result is a good corrective to a tidy story. Decomposition is usually taught as a property of the material — this leaf rots fast, that one slowly — and litter mixtures repeatedly decompose faster or slower than their parts predict. The direction is not reliably predictable, and the mechanism is unresolved. That is the finding, and reporting it as one is more useful than choosing a plausible explanation.

The research behind this page

7 studies, newest first. Each one has a page explaining what it found and what it could not show.

2017Nature Ecology & Evolution

A test of the hierarchical model of litter decomposition

Local factors — soil conditions and decomposer community — explained substantially more variation in decomposition than the hierarchical model predicts, and climate alone was a poorer predictor at the scales tested than commonly assumed.

2015Nature

The contentious nature of soil organic matter

Soil organic matter is better described as a continuum of progressively decomposing fragments than as discrete humic macromolecules.

2013Global Change Biology

The Microbial Efficiency-Matrix Stabilization (MEMS) framework integrates plant litter decomposition with soil organic matter stabilization: do labile plant inputs form stable soil organic matter?

The easily digested parts of litter — sugars and simple compounds — are converted efficiently into microbial tissue, and it is that microbial material which ends up bound to mineral surfaces and persisting.

2005Annual Review of Ecology, Evolution, and Systematics

Biodiversity and litter decomposition in terrestrial ecosystems

Mixing litter species frequently produces decomposition rates that differ from those predicted by the species alone, in both directions.

2004Ecology Letters

Detritus, trophic dynamics and biodiversity

Detritus supports food webs whose dynamics differ from grazing webs in important respects: the resource does not respond to its consumers, inputs arrive independently of consumption, and the resulting couplings can stabilise or destabilise the wider community depending on structure.

2004Science

Ecological linkages between aboveground and belowground biota

Above-ground and below-ground communities are reciprocally linked.

1999The American Naturalist

Patterns in the fate of production in plant communities

The share of plant production eaten alive varies enormously between ecosystem types, from a small minority in forests to a large majority in phytoplankton systems.

This page is a stop on a longer route

A guided journey reads several subjects in a deliberate order, with an argument for why one follows another. You can join in the middle.

Where to go from here

Each of these follows from something on this page — a relationship in the evidence, a claim people ask about, or the next mechanism along.

How complete this page is, and what it is still missing

NatureHQ publishes its own gaps. This page is at 43% completeness against what we would call a finished subject, and was last reviewed on 2026-09-04. It carries 6 claims and answers 2 mapped search questions.

  • 3 high-priority search intent(s) not yet covered
  • no research from the last few years is attached — check for newer work
  • more experiments could be explained in plain English
  • no popular claim about this subject has been checked yet
  • Dissolved organic matter, a major detrital pool especially in water, is barely covered.
  • Faecal material as a detrital resource is treated on the dung pages rather than here.
  • Freshwater detrital webs are mentioned but covered on the aquatic decomposition page.