The environmental costs of agriculture include greenhouse gas emissions, water pollution, biodiversity loss, soil degradation, freshwater depletion, and chemical contamination of ecosystems. If you encountered this as a multiple-choice question, any of these would be a correct answer. Agriculture and related land use account for roughly 21% of total global greenhouse gas emissions, making farming one of the largest single drivers of environmental change on the planet.
Understanding each of these costs in detail helps explain why agriculture shows up so frequently in environmental science courses and policy debates. Here’s what each one actually looks like.
Greenhouse Gas Emissions
Agriculture, forestry, and other land use together released approximately 12 billion metric tons of carbon dioxide equivalent in 2019. That 21% share of global emissions comes from a mix of sources: livestock digestion produces methane, fertilized soils release nitrous oxide, and deforestation to clear new farmland releases stored carbon. Nitrogen fertilizer production alone is a major contributor, releasing around 465 million metric tons of carbon dioxide annually because the manufacturing process runs almost entirely on natural gas and coal.
Producing nitrogen fertilizer can account for more than 50% of the total energy consumed in commercial agriculture. Every kilogram of nitrogen fertilizer applied to a field carries a carbon footprint of nearly 7 kilograms of CO₂ equivalent, factoring in manufacturing, transport, and the nitrous oxide that escapes from soil after application.
Water Pollution and Dead Zones
Rainwater flowing off farmland carries nitrogen and phosphorus from fertilizers into streams, rivers, and eventually coastal waters. These nutrients trigger massive algae blooms. When the algae die and decompose, bacteria consume the available oxygen, suffocating fish and bottom-dwelling animals. The result is a “dead zone,” an area of water too oxygen-depleted to support most marine life. Hundreds of these dead zones now exist worldwide, with one of the largest forming every summer in the Gulf of Mexico.
The same nutrient runoff contaminates drinking water sources, increasing treatment costs for municipalities and posing health risks in rural communities that rely on well water.
Biodiversity Loss and Habitat Destruction
Expanding farmland is the single largest driver of habitat loss globally. When forests, grasslands, and wetlands are converted to cropland or pasture, the species that depend on those ecosystems lose their homes. Research published in Nature Sustainability estimates that land-use change since 1995 has committed roughly 1.5% of all global species to extinction, with Southeast Asia, Latin America, and Africa bearing over 98% of the damage.
In Brazil’s Amazon region, cattle ranching accounts for over 80% of deforestation. In the Cerrado, a biologically rich savanna, that figure climbs to 88%. Soybean production, often blamed for deforestation, has mostly expanded onto land that was already cleared for other uses rather than pushing directly into intact forest.
Pesticide Damage to Pollinators and Soil Life
Pesticides don’t just kill target pests. They disrupt the microorganisms that keep both soil and pollinators healthy. In honeybees, certain common pesticides reduce total gut bacteria by as much as 90%, wiping out beneficial microbes that regulate immune function and block pathogens. Neonicotinoids, a widely used class of insecticides, suppress bee immune systems and are linked to declining populations of bees, birds, bats, fish, and amphibians.
In soil, the effects are similarly broad. One older pesticide, DDT, was found to decrease active soil bacterial biomass by about 60%. Glyphosate, the world’s most widely used herbicide, increases the prevalence of root-rot fungi by suppressing the beneficial soil microbes that normally keep those pathogens in check. It also impairs mycorrhizal fungi, the underground networks that help plants absorb nutrients. Fungicides applied inside beehives reduce fungal diversity in bee food stores, leaving colonies more vulnerable to disease and nutritional stress.
Freshwater Depletion
Agriculture uses 72% of all freshwater withdrawals worldwide, dwarfing industrial use (16%) and household or service use (12%). Irrigation is the primary demand, and in many regions, water is drawn from aquifers faster than rainfall can replenish them. The Ogallala Aquifer beneath the U.S. Great Plains, for example, has dropped dramatically in areas of heavy irrigation, threatening the long-term viability of farming in the region.
Irrigation also carries a secondary cost: salinization. When water evaporates from irrigated fields, it leaves dissolved salts behind in the soil. Over time, salt concentrations build to levels that stunt plant growth and reduce yields. Globally, about 50% of all irrigated land is now affected by salinity. In the United States, yield reductions from salt damage occur on an estimated 30% of irrigated acreage.
Soil Erosion and Degradation
Topsoil, the nutrient-rich upper layer that crops depend on, erodes far faster on farmland than it forms. Current models estimate that roughly 36 billion tons of soil erode globally each year, largely due to tillage, overgrazing, and leaving fields bare between growing seasons. Soil naturally regenerates at a rate of about one inch per several hundred years, meaning erosion at this scale is effectively permanent on any human timescale.
Conservation practices like no-till farming, cover cropping, and contour plowing could prevent over a billion tons of that annual loss if widely adopted. But adoption remains inconsistent, and degraded soils require increasing amounts of synthetic fertilizer to maintain yields, which feeds back into the emissions and water pollution problems described above.
Air Quality
Livestock operations and fertilized fields release large quantities of ammonia into the atmosphere. That ammonia reacts with other pollutants to form fine particulate matter (PM2.5), the tiny particles that penetrate deep into human lungs and are linked to heart disease, stroke, and respiratory illness. In Europe, agricultural ammonia is responsible for the formation of roughly 50% of all PM2.5. In the United States, the figure is about 30%. This makes farming a surprisingly significant contributor to air pollution, even in urban areas far from the fields themselves.