Earthworms, millipedes, woodlice, and springtails do the least glamorous job in nature. They chew through dead leaves, rotting roots, and fallen wood, breaking it into fragments that fungi and bacteria can finish off. That chewing is not a minor detail. It sets the pace at which carbon and nutrients move through soil, which is where most of the planet's terrestrial life and biomass actually sit. A new synthesis says this quiet machinery is losing power almost everywhere researchers have looked.
Writing in Current Biology, a team led by Rui Yin pulled together 650 measurements from 55 separate studies to ask a blunt question. When you push a soil ecosystem with the kinds of stress humans now apply routinely, what happens to how much the detritivores eat? The answer: feeding activity dropped by 47.8 percent on average. Nearly half, gone, across a huge range of habitats and animals.
Drought hits harder than heat
The meta-analysis sorted the damage by cause. Climate change came out worst, knocking feeding activity down by 59.8 percent. Chemical pollution was close behind at 57.6 percent. Fire cut it by 49.1 percent, and turning land over to intensive agriculture lowered it by 34 percent.
What stands out is the split inside the climate category. Warming on its own reduced feeding by 25.4 percent, which is real but modest. Drought reduced it by 68.9 percent. Soil animals are mostly built for damp conditions; springtails and worms move, breathe, and feed through thin films of water in the pore spaces between soil grains. Dry that out and they slow down, retreat, or die. As many regions swing toward longer dry spells, that number is the one worth remembering.
Chemicals told a similar story of a few bad actors doing most of the harm. Insecticides were close to a total shutdown, suppressing feeding by 98.9 percent. Fungicides came in at 59.7 percent and heavy metals at 59.5 percent. Insecticides target arthropods for a living, so their effect on non-target soil arthropods should not shock anyone, but seeing the near-elimination laid out against a global dataset is sobering.
Not every farming practice is equal
The land-use findings were more nuanced, and that nuance matters for anyone deciding how to manage soil. Within intensive agriculture, mineral fertilization drove most of the decline at 45.6 percent. Grazing had a smaller effect, 20.3 percent, and tillage smaller still at 11.8 percent. So the story is not simply that farming ruins soil biology. Some interventions bite hard, others barely register, and that opens room for choices that keep the underground food web functioning.
The size of the hit also depended on the setting. Ecosystem type mattered. So did soil organic carbon and soil pH, and so did how many detritivore species were present and how abundant they were. Communities richer in species and individuals tended to absorb the blow better, which lines up with a long-running theme in ecology: diversity buffers a system against shocks.
Why a slower gut matters aboveground
Feeding activity is not just a curiosity about invertebrate appetites. It is the throttle on decomposition. When detritivores eat less, dead plant material piles up more slowly into usable nutrients, and the transfer of energy up through soil food webs stalls. The authors frame this as a threat to core ecosystem functioning, including the cycling of carbon that soils either lock away or release.
Some caution is in order here. This is a meta-analysis, so it inherits whatever biases sit in its 55 source studies, and those studies lean toward particular regions and particular measurement methods, often litterbag or bait-lamina tests that stand in for real feeding. Reduced feeding in an experiment is also not the same as a documented collapse in carbon cycling out in the field; the link to ecosystem outcomes is inferred, not directly measured across all sites. And averages hide the spread. A 47.8 percent mean is built from cases that ranged from mild to near-total.
Still, the direction is hard to argue with, and it points the same way whether the stressor is a drying climate, a sprayed pesticide, or a bag of fertilizer. The animals that keep soil alive are eating less, and they are doing it across continents at once. Much of what keeps land productive happens where nobody is watching, in the dark, a few centimeters down.
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