The global biomass of wild mammals

Greenspoon, Lior; Krieger, Eyal; Sender, Ron; Rosenberg, Yuval; Bar-On, Yinon M.; Moran, Uri; Antman, Tomer; Meiri, Shai; Noor, Elad

doi:10.1073/pnas.2204892120

Cited by 55 publications

(50 citation statements)

References 32 publications

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“…While our estimates are substantially larger than several previous macroecological studies (Barnosky, 2008;Bar-On et al, 2018;Greenspoon et al, 2023), our results are comparable in magnitude to several recent estimates that rely on empirical local animal counts (Fløjgaard et al, 2022;Manzano et al, 2023). Fløjgaard et al (2022) report a bimodal distribution of empirical large-herbivore biomasses in Europe with high numbers in trophic rewilding sites in line with our estimates and small numbers in the defaunated 'wild' nonrewilding areas.…”

Section: Wild Mammal Biomasssupporting

confidence: 88%

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Late‐Quaternary megafauna extinctions have strongly reduced mammalian vegetation consumption

Pedersen

Faurby

Svenning

2023

Global Ecol Biogeogr

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AimHow much stronger would the effects of herbivorous mammals be in natural ecosystems if human‐linked extinctions and extirpations had not occurred? Many mammal species have experienced range contractions, and numerous species have gone extinct in the late Quaternary, completely or in large part linked to human pressures. Therefore, herbivore consumption rates in seemingly natural ecosystems will deviate from their pre‐anthropogenic state. Here, we estimate the size of this deviation.LocationTerrestrial systems, globally.Time periodCurrent.Major taxa studiedAll late‐Quaternary terrestrial mammals.MethodsWe estimated and mapped vegetation consumption rate by all late‐Quaternary terrestrial mammals. We did this through the estimation of natural densities and dietary needs. We mapped their consumption rate in both current ranges and present‐natural ranges, that is estimated ranges in the absence of human‐linked range contractions and extinctions. We compared these estimated consumption rates to current net primary productivity (NPP). We summarized the results across ecosystem types everywhere as well as for only the last remaining wilderness areas.ResultsWe estimate that wild mammals consume a median of 11% of NPP (at the scale of 96.5 km × 96.5 km grid cells) in current natural areas and that this would have been much higher in the absence of extinctions and extirpations, namely 21%. Looking at the change per grid cell, the mammal losses result in a median 42% reduction in consumption rate. Importantly, we estimate very similar declines in herbivory in what are considered the last remaining wilderness areas.Main conclusionsOur results suggest that the natural interaction of mammalian herbivores with vegetation in ecosystems across the world is strongly reduced by prehistoric and historic to recent species losses, even in the last remaining wilderness areas, likely with major effects on ecosystem structure and functioning.

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Section: Wild Mammal Biomasssupporting

confidence: 88%

“…Current mammal livestock biomass has been estimated to be 0.1 PgC and only 0.003 PgC in current wild mammal populations (Bar‐On et al, 2018; Greenspoon et al, 2023). Thus, the estimated current‐day mammal biomass, including livestock, is somewhat smaller than what we estimate to be the present‐natural biomass of wild mammals.…”

Section: Discussionmentioning

confidence: 99%

Late‐Quaternary megafauna extinctions have strongly reduced mammalian vegetation consumption

Pedersen

Faurby

Svenning

2023

Global Ecol Biogeogr

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“…The global HFT classification and REMAP lay the foundation for showing how mammals influence biogeochemical cycling, greenhouse gas fluxes, and vegetation dynamics. Our current model does not include all feedbacks between animals and ecosystems, but a foreseeable application would be to fully-couple REMAP with global vegeattion models and include invasive species and livestock, which today comprise the largest herbivore biomass pool (Greenspoon et al, 2023). Further, we envision integration with Earth-system models to demonstrate the influence of mammals in biosphere-atmosphere feedbacks.…”

Section: Discussionmentioning

confidence: 99%

“…S1). Various statistical methods have been used to estimate mammals density/biomass to complement empirical data (Greenspoon et al, 2023; Santini, Isaac, Maiorano, et al, 2018; Vidal-Cordasco et al, 2022). We thus generated density estimates for the missing locations and species using a spatial linear mixed-effects regression following (Santini, Isaac, Maiorano, et al, 2018).…”

Section: Methodsmentioning

confidence: 99%

Trait-based mechanistic approach highlights global patterns and losses of herbivore biomass functional diversity

Zhu

Alroy

Ciais³

2021

Preprint

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Terrestrial mammalian herbivores strongly shape ecosystems and influence Earth system processes. Herbivorous mammals can alter vegetation structure, accelerate nutrient distribution, and modify carbon cycling. The Late Pleistocene megafauna extinctions triggered significant changes in ecosystems and climate, and current extinctions are having similarly pervasive consequences. A lack of global dynamic models of mammal populations limits our understanding of the ecological role of wild mammals and the consequences of their past and future extinctions. Here we present a global model of herbivore mammal populations defined by their ecological role based on a classification of all extant herbivores (n = 2599) in 24 functional groups. The eco-physiological model predicts present-day mammal biomass in natural conditions. Biomass hotspots occur in areas today dominated by humans, which account for 30% of biomass loss and limit future rewilding potentials. Large herbivore (body mass > 5 kg) biomass is higher in hot and wet areas with high evapotranspiration. Conversely, small herbivore biomass is more evenly distributed, particularly in colder climates. Thus, energy-water dependency is higher in large herbivores than smaller ones. Negative deviations from the biomass and water-energy relationship unveil past extinction patterns. Late Pleistocene extinctions may have triggered a collapse of biomass in Australia and South America and heavy losses in North America and northern Asia. The herbivore biomass estimates provide a quantitative benchmark for conservation and management actions. The herbivore model and the functional classification create new opportunities to integrate mammals into Earth system science.

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“…Livestock comprise by far the largest mammalian biomass on Earth [1,2] and play a fundamental role in human wellbeing through direct contributions to food security and nutrition, as well as supporting crop production, supplementing income, providing employment, and fulfilling social or cultural needs [3][4][5]. However, heat stress is already a major problem for animal husbandry, costing as much as USD 1.7 billion annually in the USA alone, mostly in the dairy industry [6].…”

Section: Introductionmentioning

confidence: 99%

Global risk of heat stress to cattle from climate change

North,

Franke,

Ouweneel

et al. 2023

Environ. Res. Lett.

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Cattle farming is a major source of global food production and livelihoods that is being impacted by climate change. However, despite numerous studies reporting local-scale heat impacts, quantifying the global risk of heat stress to cattle from climate change remains challenging. We conducted a global synthesis of documented heat stress for cattle using 164 records to identify temperature-humidity conditions associated with decreased production and increased mortality, then projected how future greenhouse gas emissions and land-use decisions will limit or exacerbate heat stress, and mapped this globally. The median threshold for the onset of negative impacts on cattle was a temperature-humidity index of 68.8 (95% C.I.: 67.3–70.7). Currently, almost 80% of cattle globally are exposed to conditions exceeding this threshold for at least 30 days a year. For global warming above 4°C, heat stress of over 180 days per year emerges in temperate regions, and year-round heat stress expands across all tropical regions by 2100. Limiting global warming to 2°C, limits expansion of 180 days of heat stress to sub-tropical regions. In all scenarios, severity of heat stress increases most in tropical regions, reducing global milk yields. Future land-use decisions are an important driver of risk. Under a low environmental protection scenario (SSP3-RCP7.0), the greatest expansion of cattle farming is projected for tropical regions (especially Amazon, Congo Basin, and India), where heat stress is projected to increase the most. This would expose over 500 million more cattle in these regions to severe heat risk by 2090 compared to 2010. A less resource-intensive and higher environmental protection scenario (SSP1-RCP2.6) reduces heat risk for cattle by at least 50% in Asia, 63% in South America, and 84% in Africa. These results highlight how societal choices that expand cattle production in tropical forest regions are unsustainable, both worsening climate change and exposing hundreds of millions more cattle to large increases in severe, year-round heat stress.

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The global biomass of wild mammals

Cited by 55 publications

References 32 publications

Late‐Quaternary megafauna extinctions have strongly reduced mammalian vegetation consumption

Late‐Quaternary megafauna extinctions have strongly reduced mammalian vegetation consumption

Trait-based mechanistic approach highlights global patterns and losses of herbivore biomass functional diversity

Global risk of heat stress to cattle from climate change

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