Agriculture is the single largest driver of biodiversity loss on Earth. It reshapes landscapes on a scale no other human activity matches: roughly half of all habitable land is now used for farming, covering about 50 million square kilometers. That transformation, from forest and grassland and wetland into cropland and pasture, eliminates habitat, fragments what remains, and introduces chemicals and nutrients that ripple through ecosystems far beyond the farm itself.
The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) ranks changes in land and sea use as the most important direct driver of biodiversity decline globally, ahead of climate change, pollution, and invasive species. Agriculture, forestry, and fisheries are the primary forces behind those land-use changes. About 24% of Earth’s ice-free land surface is dedicated to growing crops, and another 26% to grazing livestock.
Habitat Loss and Fragmentation
When a forest or prairie is converted to farmland, the species living there lose their home outright. But the damage extends well beyond the cleared area. The habitat that remains gets carved into smaller, more isolated patches, and the edges of those patches degrade rapidly. Seventy percent of the world’s remaining forest sits within one kilometer of an edge, where exposure to altered light, wind, temperature, and contact with agricultural chemicals changes conditions enough to push out interior-dwelling species.
Nearly 20% of remaining forest is within just 100 meters of an edge, the zone where degradation is most severe. In the Brazilian Atlantic Forest, the proportion of forest located more than one kilometer from an edge has collapsed from about 90% historically to less than 9% today. Research on fragmented habitats shows that breaking continuous ecosystems into smaller pieces reduces species richness by 13 to 75%, depending on the landscape, and also impairs ecosystem functions like biomass production and nutrient cycling. Species that need large, unbroken territory, such as large predators and certain migratory birds, are hit hardest.
Pesticides and Insect Decline
Insects underpin much of the food web. They pollinate crops and wild plants, decompose organic matter, and feed birds, bats, and fish. A landmark study in German nature reserves documented a decline of more than 75% in total flying insect biomass over 27 years. These were protected areas, not farmland, yet they were surrounded by intensive agriculture. The researchers pointed to agricultural intensification, including pesticide use, year-round tillage, and heavy fertilizer application, as a plausible explanation.
Pesticides rarely stay where they’re applied. They drift on wind, wash into streams, and accumulate in soil. Insecticides designed to kill crop pests also kill beneficial insects: wild bees, beetles, butterflies, and the larvae of countless species that never touch a crop plant. Herbicides eliminate the wildflowers and weedy margins that pollinators and other insects depend on for food and shelter. The result is a landscape that produces calories efficiently but supports far less life.
Fertilizer Runoff and Water Ecosystems
Synthetic nitrogen and phosphorus fertilizers boost crop yields, but plants only absorb a fraction of what’s applied. The rest washes off fields and into rivers, lakes, and eventually coastal waters. This excess of nutrients triggers explosive algal growth. When those algae die and decompose, the process consumes dissolved oxygen, creating low-oxygen “dead zones” where fish, shellfish, and other aquatic organisms suffocate or flee.
The Gulf of Mexico dead zone, fed by nutrient runoff from farms across the Mississippi River basin, is one of the largest in the world and recurs every summer. Hundreds of similar dead zones have been documented in coastal waters globally. Freshwater systems suffer too: lakes choked with algal blooms lose the clear-water conditions that support diverse fish, amphibian, and aquatic plant communities. Even groundwater can be affected, carrying nitrates into springs and wetlands that once supported unique species.
Soil Biodiversity Under Pressure
A handful of healthy soil contains billions of microorganisms: bacteria, fungi, nematodes, and other tiny creatures that decompose organic matter, cycle nutrients, and suppress plant diseases. Conventional farming practices, particularly heavy tillage, synthetic chemical inputs, and monoculture planting, reduce the diversity and abundance of these soil communities.
Research comparing organic and conventional farming systems found that organic practices can boost microbial populations by roughly 34% and support measurably higher microbial diversity. Organic soils also showed greater microbial activity, indicating more dynamic nutrient cycling. This matters because soil organisms are the foundation of terrestrial food webs. When soil biodiversity declines, the land becomes more dependent on external inputs to stay productive, creating a cycle that further marginalizes the organisms that once maintained fertility naturally.
Loss of Crop Genetic Diversity
Agriculture doesn’t just reduce wild biodiversity. It has also dramatically narrowed its own genetic base. Over the past century, about 75% of plant genetic diversity has been lost as farmers worldwide shifted toward high-yielding, genetically uniform crop varieties. Today, just nine plant species account for 66% of global crop production, and three of those (rice, wheat, and maize) supply more than half of all plant-derived calories consumed by humans.
This genetic uniformity is a form of biodiversity loss with direct practical consequences. A genetically diverse crop population has natural variation that helps it withstand new pests, diseases, or shifts in climate. A genetically narrow one is vulnerable to being wiped out by a single threat. The Irish Potato Famine, caused by a disease that swept through genetically similar potato crops, is a historical example of this risk. The same dynamic plays out on a smaller scale every year when pest or disease outbreaks hit modern monocultures.
Traditional and heritage crop varieties, along with the wild relatives of domesticated plants, carry genetic traits that could prove essential for adapting food systems to future challenges. But many of these varieties are disappearing as farmers adopt standardized commercial seeds. Gene banks preserve some of this diversity, though they can’t fully replicate the ongoing evolutionary adaptation that happens when diverse crops grow in diverse environments.
Livestock Grazing and Grassland Loss
Livestock grazing occupies more land than crop production, covering roughly 26% of Earth’s ice-free surface. In many regions, natural grasslands, savannas, and scrublands have been converted to managed pasture, often involving the removal of native vegetation and the introduction of non-native forage grasses. Overgrazing compacts soil, reduces plant diversity, and degrades the habitat that ground-nesting birds, small mammals, reptiles, and invertebrates rely on.
In tropical regions, cattle ranching is a primary driver of deforestation. The expansion of pastureland in the Amazon and other tropical forests eliminates some of the most species-rich ecosystems on the planet. Even in temperate zones, the conversion of native prairie to grazed or hayed grassland has contributed to steep declines in grassland bird populations.
How Farming Practices Can Reduce the Damage
Not all farming affects biodiversity equally. The scale of impact depends heavily on how land is managed. Practices like maintaining hedgerows, buffer strips, and patches of native vegetation within and around farmland give wildlife corridors and refuge habitat. Reducing pesticide use, rotating crops, and integrating cover crops help sustain soil organisms and the insects that depend on diverse plant communities.
Agroforestry, which combines trees with crops or livestock, can support significantly more species than open monoculture while still producing food. Precision agriculture, which applies fertilizers and pesticides only where and when needed, cuts the chemical load that leaks into surrounding ecosystems. Organic farming, while not a universal solution, consistently supports higher biodiversity on and around the farm compared to conventional methods.
The core tension is that feeding eight billion people requires enormous amounts of land and inputs, and every choice about how to farm that land has consequences for the species that share it. Intensifying production on existing farmland can spare wild habitat from conversion, but only if that intensification doesn’t rely on the chemical-heavy methods that degrade the land already in use. The most biodiversity-friendly food systems tend to blend high efficiency with deliberate habitat preservation, treating the farm not as an isolated production unit but as part of a larger living landscape.