Livestock, land use, and biodiversity

Global land is a finite resource, 54% of which consists of rangelands that support pastoralists, wildlife, and carbon storage but are underrepresented in national climate plans. Of the 4.9 billion hectares used for agriculture, 80% is dedicated to livestock, with grazing land comprising the majority of 3.4 billion hectares and feed crops occupying 0.5 billion hectares of arable land. Cattle require significantly more land than other livestock, using 28 times more on average. Expanding agricultural land to meet rising food demands risks deforestation, biodiversity loss, and climate impacts, while aquaculture poses ecosystem threats. To mitigate these issues, the FAO calls for zero deforestation and elimination of illegal fishing by 2030–2050. Alternative land-use strategies include rewilding, converting pastures to cropland, or afforestation to sequester carbon. Vegan or vegetarian systems, with lower animal-to-plant ratios, could reduce land use. However, implementing these alternatives faces practical challenges and complex trade-offs, highlighting the need for integrated, region-specific solutions.

Land is not a homogeneous or fully flexible resource, with significant portions unsuitable for conversion to crops. Globally, non-convertible pastures and rangelands make up a quarter of agricultural land, and only one third of current grasslands used for livestock can potentially be converted to cropland. High-productivity lands are already used for crops and typically have low biodiversity. Arable land availability varies significantly by region. For example, countries like Germany, Denmark, France, and Spain have 50–60% arable land, whereas most Nordic countries have less than 10%. Norway has only 3% arable land, but 45% of its land is suitable for pasture, with grain production there more suited for livestock feed due to climate conditions. Similarly, in Wales, 81% of farmland is permanent grassland, unsuitable for growing other types of food. These variations highlight the need for region-specific approaches to land use and agricultural planning.

Livestock's key strength lies in its ability to utilize marginal lands with low opportunity costs for arable production. Eliminating livestock could reduce total land use for food by some 75%, but arable land use would only decrease by about 20%. However, such shifts involve trade-offs, as livestock contributes to nutrition, livelihoods, and biodiversity when managed sustainably. Non-convertible grasslands, comprising two-thirds of grazing land, would need to be withdrawn from the food system if not used for livestock, potentially undermining food security. Regions suitable for rewilding or afforestation often overlap with areas where livestock is crucial for local livelihoods and food security. Climate change will likely render more land marginal in the future, making livestock increasingly vital for food security in affected areas. These factors underscore the important role of livestock in balancing ecological, economic, and social goals.

Nutritional metrics significantly impact comparisons of land use across food types. While land use is often measured per kilogram of food or protein, adjusting for protein digestibility, essential amino acids, and micronutrients alters outcomes. As a result of nutritional corrections, beef and cheese show reduced land use, beans and peas fare worse, and eggs and pork may rival or outperform maize and wheat in efficiency. Animal-source foods also provide vital minerals and vitamins, further influencing land-use assessments. Moreover, reducing food waste, particularly ultra-processed foods—which contribute significantly to waste and land use without essential nutritional value—should be prioritized. Ultra-processed foods drive deforestation through increased demand for crops like palm and soy oil in biodiversity-rich areas. In some diets, categories like sweets, snacks, and drinks, particularly cocoa, oils, coffee, and nuts, contribute disproportionately to biodiversity loss.

Animal husbandry can contribute to harmful outcomes like deforestation and biodiversity loss, with some authors advocating plant-based diets to restore ecosystems. While biodiversity concerns are valid, claims such as a >50% vertebrate decline since 1970 are overstated, as extreme losses are limited to 1% of populations. In Europe, mammal diversity remains comparable to 8,000 years ago, and reintroducing extirpated species or their domestic descendants could enhance ecosystems. The debate over biodiversity conservation often contrasts land sparing (high-yield farming to enable rewilding) with land sharing (wildlife-friendly farming). Land sparing is argued to improve biodiversity in protected areas, but critics find this approach unsustainable in the long term. Instead, integrating biodiversity conservation into human landscapes is proposed as a more effective strategy to prevent ecosystem collapse and mass extinction. Conservation strategies should be tailored to specific contexts and targets to balance ecological and agricultural needs.

The debate between animal- and plant-based agriculture is more nuanced than a simple dichotomy. The biodiversity impact or deforestation caused by agriculture depends on practices and how environmental variability is managed. Both plant and animal farming can be regenerative or destructive, as seen in examples like deforestation linked to avocado cultivation. Deforestation for soy is often linked to livestock feed, but a significant portion of soy's value also comes from oil and bioethanol production. Furthermore, this deforestation is driven by land speculation and economic expansion rather than farming alone. Even without agriculture, activities like logging and mining would continue to contribute to deforestation. The issue lies not only in livestock farming per se but in the broader extractive industrial model, which must be addressed at its core.

The conversion of natural ecosystems to agriculture is a major threat to biodiversity, but this generalization obscures significant variations between agricultural systems. Globally, crop production has about twice the negative impact on biodiversity compared to livestock, while rangelands often enhance habitat diversity. In Europe, grasslands support half of endemic plant species and many bird species, making grassland-to-arable-land conversion a key driver of biodiversity loss. Both crop and livestock systems, however, can be either beneficial or harmful, depending on management practices. Cereal crops, widely used for food and feed, are a significant threat to biodiversity due to habitat simplification, deforestation, and monoculture practices. Similarly, starchy roots, oil crops, and pulses contribute to biodiversity loss when grown in monocultures. Ultra-processed foods—often derived from such crops—are linked to 35-45% of diet-related biodiversity losses in high-income countries. Converting row crop lands to well-managed pastures could improve soil health and biodiversity. Integrating livestock and crop systems can further enhance soil fertility and sustainable crop production. However, poorly managed grazing, akin to land clearing, can fragment habitats and degrade ecosystems. Sustainable management of both crop and livestock systems is crucial for minimizing biodiversity impacts and enhancing ecosystem resilience.

Semi-natural grasslands support significant biodiversity, depending on factors like grazing management. Properly moving livestock through well-connected core habitats enhances functional connectivity and aids plant dispersal. Incentives to protect rangeland mobility and prevent fragmentation can align livestock production with the preservation of plant and wildlife diversity, demonstrating that biodiversity can thrive under effective grazing strategies. Grazing techniques that mimic wildlife behavior, such as multi-paddock systems inspired by bison grazing in the North American Great Plains, can recreate evolutionary grazing patterns. These approaches foster biodiversity by creating shifting focal patches, promoting a richer soil microbiome, and improving soil health. Regenerative ranchers like Gabe Brown have reported remarkable increases in soil organic matter, although these outcomes are context-dependent and require more formal validation in peer-reviewed research. Overall, well-managed grazing offers potential benefits for soil health, biodiversity, and ecosystem resilience, emphasizing the importance of integrating ecological principles into livestock management.

Open ecosystems, such as grasslands, savannas, and woodland-grassland mosaics, co-evolved with large grazing animals over millions of years. Grazing by ruminants helped shape carbon-rich soils in semi-arid to semi-humid regions, and over the past 20 million years or more, the expansion of these grassy biomes created productive, carbon-storing landscapes. From around 18 million years ago, such open grass-dominated landscapes became widespread, supporting abundant large herbivores. During the Pleistocene, they covered nearly half of the Earth's land surface, forming one of the planet's most extensive ecosystems. Even in Europe, the temperate landscape was not primarily closed-canopy forest but a dynamic mosaic of open woodlands, grasslands, and scattered trees like hazel, oak, and yew. Many of the native plants thrive in semi-open, frequently disturbed conditions rather than deep shade. Large herbivores played a crucial role in maintaining this openness through grazing and disturbance, with densities far higher than today's low levels in most areas. 

Human history has long been deeply connected to these grassy biomes, as many areas now used for livestock farming were originally grasslands, not forests. Dense, uniform forests only became dominant in many regions after the decline of wild megafauna at the end of the Pleistocene, the loss of early human management practices like burning and hunting, and shifts in land use, though domestic livestock since the Neolithic helped restore some grazing functions through widespread, year-round herding that persisted until modern industrial times. Even today, some grasslands have persisted open since the end of the last glacial period, sustained by grazing, fire, and human activities rather than being overgrown by closed forests, as is the case in the Transylvanian forest-steppe.

Recognizing woodland-grassland mosaics as the long-term natural baseline has important consequences for conservation and rewilding. Many current conservation efforts are biased toward forests, promoting large-scale tree planting on open lands once considered ‘degraded’ or deforested, even though these areas naturally supported grassy or mosaic ecosystems maintained by fire and grazing. Such ill-conceived initiatives, incentivized by carbon credit schemes, could actually harm biodiversity and ecosystem dynamics. Planting flammable tree species in grasslands endangers biodiversity and offers limited climate benefits, particularly under the threat of forest fires, while it may negatively impact rural communities and can harm biodiversity, as seen with monoculture plantations in New Zealand replacing traditional sheep farming. Moreover, suppressing grazing can heighten wildfire risks. Without herbivores to consume grass, dead plant material builds up as fine, highly flammable fuel, increasing the chance and intensity of fires while allowing shrubs and woody growth to invade. 

Rather than displacing livestock by trees, biodiversity strategies could include the expansion of agricultural systems that integrate both, similar to traditional wood-pastures found in places like the Iberian dehesas. Sustainable management of rangelands, emphasizing pastoralism and recognizing their unique ecological functions, provides a more balanced approach to combating desertification and climate change than the current focus on dense afforestation. To do so, healthy open and mosaic ecosystems will depend on managed grazing that mimics the ecological roles once played by ancient large herbivores.