Insects underpin nearly every terrestrial and freshwater ecosystem on Earth, performing roles so varied and interconnected that removing them would unravel food webs, starve soils, collapse crop yields, and leave dead organic matter piling up with nowhere to go. They pollinate roughly three-quarters of flowering plant species, recycle nutrients from dung and decaying matter back into the ground, control pest populations from the inside, feed the birds and fish that humans depend on, and physically reshape the soil beneath our feet. The scale of their contribution is staggering, and the evidence behind each of these roles has grown sharper in recent decades as researchers measure exactly what happens when insects are present and what falls apart when they are not.
Reshaping Soil from the Inside
When people think of soil health, earthworms tend to get the credit. But in drier parts of the world, ants and termites do the heavy lifting. A field experiment in Australia showed that ants and termites increased wheat yield by 36%, primarily because their tunnels improved water infiltration and boosted soil nitrogen availability.1PubMed Central. Ants and termites increase crop yield in a dry climate That is not a marginal bump. In regions where rainfall is scarce and every drop matters, the tunnel networks these insects build act as underground plumbing, drawing water deeper into the soil profile where plant roots can actually use it.
Beyond water, ants and termites physically rearrange soil particles. They transport material between layers, mix organic matter into deeper horizons, and alter the structure of the ground in ways that persist long after individual colonies die off.2Australian Journal of Soil Research. The role of termites and ants in soil modification – a review In arid climates, where traditional earthworm populations are sparse, these insects are the primary biological engineers keeping soil functional. As drought-prone regions expand with climate change, this role is only going to matter more.
Recycling Nutrients from Dung and Dead Matter
One of the less glamorous but most critical insect functions is breaking down waste. Dung beetles are the stars here. When large herbivores leave droppings on grasslands or savannas, dung beetles move in, break the material apart, and bury it underground. This burial increases nutrient concentrations in the soil profile, and different beetle species handle different nutrients, meaning a diverse beetle community recycles more thoroughly than any single species could alone.3CATENA. Dung beetles and nutrient cycling in a dryland environment Large-bodied dung beetles have a particularly outsized effect, enriching soil macronutrients by an average of about 45% compared to plots where dung simply sat on the surface and leached passively.4PubMed Central. The Effect of Dung Beetle Size on Soil Nutrient Mobilization in an Afrotropical Forest
The process also matters for carbon. Dung beetles that tunnel into the soil move carbon deeper into the ground, where it feeds microbial communities rather than being lost to the atmosphere through surface decomposition. When tunneling and dwelling beetle species work together, soil microbial activity increases more than either species achieves alone, suggesting that beetle diversity is itself a driver of carbon cycling efficiency in grasslands.5Soil Biology and Biochemistry. Complementarity of dung beetle species with different functional behaviours influence dung–soil carbon cycling Without dung beetles, pastures accumulate surface waste, nutrients stay locked up in dried pats, and the microbial communities below ground that plants depend on for nutrient access go underfed.
Pollination and What It Means for Your Food
Pollination is probably the insect function most people have heard about, but the scale of it still surprises. Insect pollination enhanced average crop yield between 18% and 71% depending on the crop in a study that measured the difference between fields with full insect access and fields where pollinators were excluded.6PubMed Central. Contribution of insect pollinators to crop yield and quality varies with agricultural intensification It is not just about getting more fruit or grain. Crop quality improves, too: oilseed rape had higher oil content when well pollinated, buckwheat produced fewer empty seeds, and strawberries received better commercial grades.
Economically, one widely cited analysis put the value of insect pollination for world agriculture at roughly €153 billion as of 2005, measuring the share of global food production that depends directly on pollinating insects.7Ecological Economics. Economic valuation of the vulnerability of world agriculture confronted with pollinator decline That figure would be considerably higher today, given increases in both crop production and prices. Beyond agriculture, pollinator diversity stabilizes pollination during environmental disturbances and helps wild plant communities weather climate fluctuations.8PubMed Central. Pollinator diversity benefits natural and agricultural ecosystems, environmental health, and human welfare This matters because a system reliant on one or two pollinator species is fragile; a diverse pollinator community builds in redundancy.
Natural Pest Control
Predatory and parasitic insects quietly suppress populations of species that would otherwise devastate crops. When researchers experimentally removed natural enemies from winter wheat fields, the results were dramatic. Removing ground-dwelling predators (spiders, beetles) led to an 18% increase in aphid populations. Removing flying predators and parasitoid wasps led to a 70% increase. Removing both groups at once produced a 172% spike in aphids.9PubMed Central. Relative importance of predators and parasitoids for cereal aphid control The parasitoid wasps, which lay their eggs inside pest insects and kill them as they develop, appeared to contribute the strongest effect.
This kind of biological control is the backbone of organic farming. Conservation biological control, the practice of providing habitats that sustain predator and parasitoid populations, allows natural enemies to regulate pest numbers without chemical inputs.10PubMed Central. How Effective Is Conservation Biological Control in Regulating Insect Pest Populations in Organic Crop Production Systems? Even in conventional farming, these insect predators provide a free baseline of pest suppression that would be enormously expensive to replace with pesticides alone. Remove them, and you need more spraying, which further depletes the predator populations you lost, creating a feedback loop that gets harder and more expensive to escape.
Feeding the Rest of the Food Web
Insects are not just workers in the ecosystem; they are food. A huge number of birds, bats, amphibians, reptiles, and fish depend on insects as a primary food source. This dependency is not abstract. A 29-year dataset from southern England showed that barn swallow chick survival tracked aerial insect biomass closely. In nests where at least one chick fledged, about 97% of chicks survived to fledging when insect biomass was high, compared with about 87% when biomass was at its lowest.11Ibis. Aerial insect biomass, but not phenological mismatch, is associated with chick survival of an insectivorous bird A ten-percentage-point swing in chick survival, compounded year after year, is enough to drive long-term population declines in bird species.
The food-web role extends beyond birds. Insects bridge aquatic and terrestrial ecosystems in a way that few other organisms can. In a deciduous forest in Japan, aquatic insect emergence peaked in spring, when terrestrial invertebrate prey was scarce, effectively subsidizing forest birds when they needed food most. The reverse happened in summer: terrestrial insects falling into streams supplied fish when aquatic prey was at its seasonal low. These reciprocal insect subsidies accounted for about a quarter of the annual energy budget of forest bird communities and about 44% of the energy budget for stream fish.12PubMed. Reciprocal subsidies: dynamic interdependence between terrestrial and aquatic food webs Insects are, in a real sense, the connective tissue between forests and the waterways that run through them.
Connecting Water and Land
Aquatic insects play a role that goes beyond simply feeding fish. Many species spend their larval stage underwater and emerge as flying adults, physically transporting energy and nutrients from water to land. This life cycle means they can also carry contaminants. Pollutants absorbed during the aquatic larval phase can enter terrestrial food webs when adult insects are eaten by spiders, birds, or bats, creating unexpected pathways for chemical exposure far from the original water source.13PubMed. Contaminant fluxes across ecosystems mediated by aquatic insects
The presence or absence of aquatic predators changes the character of these insect exports. When fish are removed from aquatic habitats, the emerging adult insect communities have both higher total biomass and a higher proportion of predatory insects, which alters how the insect subsidy affects the surrounding terrestrial food web.14PubMed. Aquatic predation alters a terrestrial prey subsidy In other words, what lives in a pond changes what lives in the forest around it, and insects are the messengers carrying that influence back and forth.
Shaping Which Plants Grow Where
Insect herbivores do not just eat plants; they reshape entire plant communities. By preferentially feeding on dominant species, herbivorous insects can reduce competitive imbalances and allow less competitive plants to persist. One long-term study found that outbreaking plant-feeding insects indirectly promoted plant species richness by opening up light availability to suppressed understory species.15Ecological Monographs. Herbivory and Plant Species Coexistence: Community Regulation by an Outbreaking Phytophagous Insect Without herbivore pressure, dominant species would shade out their neighbors and drive down diversity.
The picture gets more nuanced when you consider that herbivory happens both above and below ground. In a controlled experiment, aboveground insect herbivores increased competitive asymmetry between plant species by preferentially attacking one species over another. But belowground herbivores (root-feeding insects) partially counteracted that effect, helping to balance competitive outcomes over time.16PubMed Central. Aboveground insect herbivory increases plant competitive asymmetry, while belowground herbivory mitigates the effect The interplay between these above- and belowground forces likely contributes to the high plant diversity seen in grasslands and meadows. Insect herbivory, far from being purely destructive, acts as a regulating force that keeps any one species from monopolizing resources.
Dispersing Seeds Underground
Ants are also responsible for spreading the seeds of a large share of forest floor plants, a process that has shaped understory plant communities for millions of years. In eastern North American deciduous forests, an estimated 30% to 40% of understory plant species produce seeds with lipid-rich attachments specifically designed to attract seed-dispersing ants.17Ecosphere. Antagonistic and mutualistic interactions alter seed dispersal of understory plants at forest edges The ants carry seeds back to their nests, eat the fatty appendage, and discard the seed in nutrient-rich nest refuse, giving it an ideal microsite for germination. When these ant communities are disrupted, as happens at forest edges, the composition of understory plants shifts measurably, with ant-dispersed species becoming scarce.
The relationship appears to be resilient under normal conditions. When researchers experimentally removed all seed food sources from ant colonies in a Connecticut forest, the ant populations held steady, and the coverage of ant-dispersed plants recovered within five years.18Food Webs. Are seed-dispersing ants elaiosome-limited? An experimental test in a Connecticut forest dominated by myrmecochorous plants But this resilience depends on intact forest habitat. Fragmentation and edge effects that reduce ant diversity can permanently alter which plant species dominate the forest floor.
Mass Emergences as Nutrient Bombs
Periodical cicadas offer one of the most dramatic illustrations of insect ecosystem influence. After spending 13 or 17 years underground feeding on root fluids, billions of cicadas emerge simultaneously, mate, die, and decompose on the forest floor. A study in a Kansas tallgrass prairie measured the 2015 emergence at 9.4 metric tons of dry mass and 1.12 metric tons of nitrogen transferred from below ground to the surface.19Ecosphere. Periodical cicada emergence resource pulse tracks forest expansion in a tallgrass prairie landscape
These pulses boost microbial biomass and nitrogen availability in forest soils, with indirect effects on plant growth and reproduction that researchers have described as “bottom-up cascades” linking underground and aboveground ecosystems.20PubMed. Periodical cicadas as resource pulses in North American forests That said, the effects can be surprisingly short-lived. A more recent experiment found that while cicada carcasses increased soil nutrient availability and changed the community composition of soil-dwelling organisms, the nutrient pulse did not measurably improve tree growth over four years.21PubMed Central. Acute resource pulses from periodical cicadas propagate to belowground food webs but do not affect tree performance Massive as these inputs are, soils appear to absorb and buffer them quickly, suggesting the biggest beneficiaries may be microbes and soil invertebrates rather than the trees themselves.
Waste Processing at Industrial Scale
Insects are also being harnessed deliberately to process human-generated waste. Black soldier fly larvae can consume brewer’s waste, pig manure, and semi-digested grass, converting organic matter into larval biomass that can then be used as animal feed or fertilizer.22Environmental Entomology. Bioconversion of Three Organic Wastes by Black Soldier Fly (Diptera: Stratiomyidae) Larvae A life cycle analysis of food waste bioconversion found that on a dry-weight basis, about 6% of the incoming food waste was transformed into fly prepupae, 51% became matured compost, and 43% was released as gas.23PubMed. Material flow analysis and life cycle assessment of food waste bioconversion by black soldier fly larvae (Hermetia illucens L.) This is not a niche curiosity. Commercial-scale insect bioconversion facilities are operating in multiple countries, turning food waste into protein and fertilizer while diverting material from landfills.
Insects in Cities
Urban areas might seem like the last place insects matter, but research tells a different story. A study of urban green spaces found that plant diversity was the dominant factor shaping insect functional group diversity, explaining up to 99% of the variation in some insect groups. Strikingly, insect diversity had a stronger effect on overall ecosystem functioning in these spaces than plant diversity did.24Urban Forestry & Urban Greening. Insects in urban green spaces directly and indirectly affect ecosystem functions by interacting with plants to build ecological networks The takeaway is that planting diverse urban gardens is not just about aesthetics; it creates the insect communities that then drive ecosystem health in the surrounding area.
Even informal green spaces, the weedy lots and unmaintained strips that city planners tend to overlook, contribute. A study in Prague found that pollinator abundance, including solitary bees, bumblebees, and butterflies, was generally higher in these informal spaces than in managed parks. Parks favored native plant species, while the scrappier sites boosted overall species richness and pollinator numbers.25Urban Ecosystems. The role of urban parks and informal green spaces in supporting the biodiversity of spontaneous flora and insect pollinators: a case study in Prague, Czech Republic For urban conservation, this suggests that not mowing every vacant lot might be one of the simplest and most effective things a city can do for pollinators.
Insects as Environmental Sentinels
Because many insect species are sensitive to chemical, thermal, and habitat disturbances and reproduce quickly, they serve as early warning systems for environmental problems. Predatory insects in particular are valued as bioindicators because their position in the food web means they accumulate the effects of stressors affecting everything below them.26UTTAR PRADESH JOURNAL OF ZOOLOGY. Predatory Insects as Indicators of Environmental Pollution: Implications for Ecosystem Health and Monitoring A decline in dragonfly populations near a stream, for instance, signals problems in water quality before chemical tests might catch them. Aquatic insects in particular have been used for decades as standardized indicators of river and wetland health, and their presence or absence tells ecologists more about long-term conditions than a one-time water sample can.
Insects as Human Resources
The relationship between insects and humans extends well beyond pollination of crops. More than 2,000 insect species are eaten worldwide, and edible insects offer protein levels between 30% and 85%, along with essential amino acids and micronutrients that often exceed what is found in conventional meat or fish.27Food Frontiers. Insects as Food and Feed Source: A Comprehensive Review on Nutritional Value, Food Safety Concern, Environmental Benefits, Economic Potential, Technological Innovations, Challenges, and Future Prospects The environmental math is equally compelling: insect farming produces far fewer greenhouse gas emissions and requires a fraction of the land and water that cattle or poultry operations demand.28PubMed Central. The Environmental and Ecological Benefits of Edible Insects: A Review
Insects have also inspired material science and engineering. Over hundreds of millions of years, they evolved adhesives, hydrophobic surfaces, locomotion systems, and sensors for light, sound, heat, and chemicals. These adaptations have been translated into real-world technology, including antireflective coatings, optical displays, and computing algorithms.29PubMed. It’s Not a Bug, It’s a Feature: Functional Materials in Insects The evolutionary history that made insects so successful also made them a library of engineering solutions that human designers keep returning to.
What Happens When Insect Populations Fall
All of the functions described above are under pressure. Insect populations are declining globally, driven by habitat loss, pollution, pesticide use, and climate change. Species with narrow ecological tolerances are particularly vulnerable because they struggle to adapt when conditions shift rapidly.30Biological Conservation. Global decline of aquatic and terrestrial insects driven by climate change and anthropogenic impacts The pattern is not uniform: the most severe declines have been documented in Northern Hemisphere regions with high human population density and intensive agriculture, while some tropical and arid-region monitoring sites show more modest or mixed trends.31PubMed Central. A window to the world of global insect declines: Moth biodiversity trends are complex and heterogeneous
The consequences of losing insect abundance and diversity ripple outward in ways that are hard to contain. Declines are expected to cascade onto ecosystem functioning and human well-being, including loss of biodiversity higher up the food web among insectivorous birds and impairment of ecosystem resilience overall.32Current Opinion in Environmental Sustainability. Insect decline, an emerging global environmental risk The flowering plants that dominate modern terrestrial ecosystems evolved alongside insect pollinators and herbivores, and this co-evolutionary relationship has been a primary engine of biodiversity on land for over 100 million years.33PubMed. The Angiosperm Terrestrial Revolution and the origins of modern biodiversity Disrupting one side of that partnership does not leave the other side intact. It rewrites the rules under which entire landscapes operate.