Biodiversity and animal agriculture

Earth is in the middle of a biodiversity collapse that rivals the great mass extinctions of the geological record, and the single largest direct driver of that collapse on land is the food system — overwhelmingly its animal component. The global assessments converge on this finding from independent directions: area, population counts, biomass accounting, and species-level risk models all point to animal agriculture as the dominant pressure on wild life.

This article synthesizes the headline evidence from IPBES, the WWF Living Planet Index, the Bar-On et al. biomass census, and the land-use projections that connect meat and dairy demand to extinction risk. It is a sub-article of the environment pillar and focuses on biodiversity specifically; climate, water, and nitrogen impacts are treated elsewhere.

The IPBES finding: one million species at risk

The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) is the biodiversity analogue of the IPCC. Its 2019 Global Assessment, synthesizing roughly 15,000 scientific and government sources, concluded that around one million animal and plant species are threatened with extinction, many within decades (IPBES, 2019). The assessment ranked the direct drivers of nature loss in order of global magnitude: “1999” land- and sea-use change first, direct exploitation of organisms second, climate change third, pollution fourth, and invasive species fifth.

Land-use change is where animal agriculture dominates. IPBES (2019) attributed more than a third of the planet’s terrestrial land surface and nearly three-quarters of freshwater resources to crop and livestock production, and identified agricultural expansion as the most widespread form of land-use change. Within agriculture, grazing and feed production account for the majority of converted area — the same 77% of farmland figure that appears in food-system syntheses (Poore & Nemecek, 2018; Benton et al., 2021).

The Living Planet Index: a 69% decline

WWF’s Living Planet Index tracks the average trend in abundance of roughly 32,000 vertebrate populations across more than 5,000 species. The 2022 report found an average 69% decline in monitored population sizes between 1970 and 2018, with freshwater populations down 83% and Latin America and the Caribbean showing the steepest regional collapse at 94% (WWF, 2022).

The LPI is a trend index, not a census — it measures change, not absolute numbers — but its signal is robust across taxa, regions, and methodology checks. The WWF report explicitly identifies habitat loss and degradation driven by unsustainable agriculture as the leading threat to monitored populations, with overexploitation, invasive species, pollution, climate change, and disease following (WWF, 2022). The geographic pattern reinforces the food-system link: declines concentrate in the tropics, which hold most of the planet’s biodiversity and most of its active agricultural frontier.

Bar-On 2018: the biomass inversion

Perhaps the most arresting single statistic in biodiversity comes from the Bar-On, Phillips & Milo (2018) census of the biomass distribution on Earth, published in PNAS. Using hundreds of primary data sources, the authors estimated the mass of carbon stored in every major taxonomic group.

Their mammal-level result is the one that travels. Of the roughly 0.16 gigatonnes of carbon locked up in mammal biomass globally, livestock account for about 0.1 Gt C (around 60%), humans for about 0.06 Gt C (around 36%), and all wild mammals combined — every whale, elephant, deer, rodent, bat, and primate on Earth — for roughly 0.007 Gt C, or about 4% (Bar-On, Phillips & Milo, 2018). The ratio of livestock to wild mammal biomass is therefore on the order of 14 to 1; the ratio of humans plus livestock to wild mammals is roughly 23 to 1.

A parallel calculation for birds found that domesticated poultry outweigh all wild birds by roughly three to one (Bar-On, Phillips & Milo, 2018). Humans have not merely hunted wild vertebrates into scarcity; we have replaced them, by mass, with the animals we breed to eat. Every expansion of that domesticated biomass is a subtraction from the wild.

Newbold 2015: local assemblages already below safe limits

The Bar-On numbers describe a global aggregate. Newbold et al. (2015) zoomed in to the local scale, using the PREDICTS database of 1.8 million records from 11,500 sites in nearly 100 countries to quantify how land use affects local biodiversity intactness. The study’s headline result: across human-dominated land uses, local species richness and total abundance had fallen on average by roughly 14% and 11% respectively relative to pristine baselines, with much larger losses of around 76.5% of originally present species in the most disturbed sites.

When aggregated spatially, Newbold et al. estimated that average local biodiversity intactness had already fallen below a proposed “safe limit” of 90% across more than half of the world’s land surface — and that conversion of remaining natural habitat to pasture and cropland would push further regions past the threshold. Pasture and intensive agriculture were among the land uses most strongly associated with intactness loss. Local assemblages, in other words, are already depleted enough that additional agricultural expansion risks ecological function itself, not merely rare-species counts (Newbold et al., 2015).

Tilman 2017: projecting the extinction curve

Tilman et al. (2017) linked dietary trajectories directly to species-level extinction risk. Using the International Union for Conservation of Nature (IUCN) habitat requirements for roughly 19,800 species of terrestrial mammals, birds, and amphibians, the authors projected that business-as-usual expansion of agricultural land by “2060” — driven largely by income-driven increases in meat and dairy consumption in developing economies — would move thousands of species closer to extinction, concentrated in biodiversity hotspots in sub-Saharan Africa, South and Southeast Asia, and Latin America.

Their mitigation scenarios are explicit about leverage. Dietary shifts toward plant-rich patterns similar to the Mediterranean, pescatarian, or vegetarian diets could greatly reduce or eliminate the projected need for further agricultural expansion and therefore greatly reduce projected extinction risk (Tilman et al., 2017). Yield improvements alone were insufficient; only dietary change combined with closing yield gaps and reducing waste kept the food system within an ecologically tolerable footprint.

Machovina, Feeley & Ripple (2015) reached a compatible conclusion in a review titled “Biodiversity conservation: The key is reducing meat consumption,” finding that livestock production is the single largest driver of habitat loss, and that even conservative dietary transitions would release enough land to stabilize or reverse major biodiversity trends.

Pollinators: the invertebrate crisis

Vertebrates dominate the public imagination of extinction, but pollinating insects are where food and biodiversity most directly intersect. The IPBES pollinator assessment (Potts et al., 2016) estimated that roughly 75% of the world’s food crops depend at least in part on animal pollination, and that pollinator populations — wild bees, butterflies, moths, hoverflies, beetles, bats, birds — are in widespread decline. Around 40% of invertebrate pollinator species (particularly bees and butterflies) face extinction risk at regional or national scales.

The drivers are the familiar ones: habitat loss from agricultural simplification, pesticide exposure (especially neonicotinoids), pathogens spread through managed honeybee stocks, climate change, and invasive species (Potts et al., 2016). Animal agriculture contributes to several of these simultaneously — monocultural feed production erases flowering habitat, manure runoff reshapes plant communities, and the sheer area demand of grazing precludes hedgerow and wildflower mosaics. A plant-rich food system that freed a substantial fraction of grazing land is among the few interventions of sufficient scale to stabilize pollinator populations.

Extinction rates: the background-to-present ratio

Current extinction rates are estimated at tens to hundreds of times the pre-human background rate and rising (IPBES, 2019). Vertebrate extinctions documented since “1500” run at roughly 100 times the background rate even under conservative accounting, and the rate is accelerating. The IPBES assessment frames this as the first period in Earth’s history in which a single species — ours, through its food, energy, and material systems — is driving a global extinction event.

The leverage again

Benton et al. (2021), in a Chatham House research paper prepared with UNEP and Compassion in World Farming, synthesized the food-biodiversity link into three mutually reinforcing levers: shift diets toward plant-based patterns, protect and restore native ecosystems on land that dietary shift would free, and farm the remaining agricultural land in more nature-friendly ways. The authors argue that dietary shift is the primary lever because it is the only one that reduces the total land footprint — the other levers operate within whatever footprint the food system demands.

The arithmetic that makes dietary shift decisive is the same arithmetic that appears in climate, water, and nitrogen analyses. Animal products use 77% of farmland and deliver 18% of calories (Poore & Nemecek, 2018). Livestock biomass exceeds wild mammal biomass roughly 14-fold (Bar-On, Phillips & Milo, 2018). Pasture and feed expansion dominate ongoing habitat conversion (IPBES, 2019; Benton et al., 2021). Every one of these numbers says the same thing from a different angle: the single fastest route to halting terrestrial biodiversity loss is to eat fewer animals.

What this means for the wild

Biodiversity is not a moral luxury or an aesthetic preference. It is the functional substrate of pollination, pest control, nutrient cycling, soil formation, climate regulation, and the cultural and spiritual lives of most human societies. Losing it is not reversible on any timescale that matters to civilizations. The evidence assembled by IPBES, WWF, Bar-On et al., Newbold et al., Tilman et al., and Benton et al. is not a collection of separate concerns; it is one finding, approached from several directions — that the way humans feed themselves, and specifically the way they farm animals, is the dominant force reshaping life on Earth.

A food system built around plants is not the only thing biodiversity needs, but it is the thing without which nothing else works. It is the land, and the wild that the land can hold.