## Introduction

Hunting of wild meat (also called bushmeat hunting) remains controversial in conservation policy and science because its net effect is detrimental to game populations when unsustainable, but often culturally and nutritionally essential for the subsistence needs of local human populations1,2,3. Unsustainable hunting can have cascading effects that suppress the long-term carbon storage capacity of natural forests by depleting large-bodied bird and mammal species serving essential ecosystem functions, such as dispersal of large-seeded carbon-dense tree species4,5. Unsustainable hunting, therefore can lead to shifts in the species composition of tropical tree assemblages that ultimately reduce the forest carbon storage capacity6,7,8,9.

On the other hand, hunting can provide a sustainable source of protein and essential micronutrients if appropriately monitored and managed10. Forecasts predict widespread protein deficiency in a range of tropical countries, and case studies suggest increased risk of anaemia in children if wild meat is insufficient11 to the point where the prevalence of child growth stunting can be negatively related to game abundance12. Despite the perils of managing human-occupied tropical wildlands13, sustainable hunting can enable the persistence of healthy wildlife populations of even less resilient low-fecundity game species while simultaneously supporting local subsistence14,15. A systematic review of 628 game hunting assessments in tropical forest areas found that only one-third were unsustainable16. Furthermore, sustainable wild meat hunting in tropical forest landscapes requires the persistence of extensive intact forest areas17,18. The alternative of supplying meat demand through local beef production from ruminant livestock involves deforestation, with strikingly detrimental repercussions for both biodiversity conservation and carbon emissions19. Land-use conversion to croplands and cattle pastures is the principal driver of deforestation worldwide20. Cattle ranching is, for instance, directly responsible for 71% of all Latin American deforestation, and pasture expansion has been the single largest driver of deforestation across the region since the 1970s21. The expansion of the livestock production sector in tropical forest countries to supply the growing demand for red meat is a crucial driver of both biodiversity loss and greenhouse gas (GHG) emissions22,23. Beef and a few other red meats, for instance, supply 1% of the world's calories but account for 25% of all emissions occurring due to land-use change24. The livestock sector also disproportionally contributes to the environmental cost of agriculture through high resource misuse, including water, land, and soils25.

As the global human population is projected to grow from 7.8 billion people today to 9.2–9.9 billion by 2050, global food demand is expected to increase substantially26. Rapidly escalating food demand will further accelerate land-use change, driving biodiversity loss and releasing substantial amounts of additional carbon into the atmosphere27. Coupling conservation of biodiversity and natural ecosystem services such as carbon storage with global scale food production for a growing human population requiring ever more animal protein is, therefore, among the most critical challenges facing humanity today28.

Tropical forests fulfil an essential service by storing an estimated 460 billion tons of carbon, more than half the total atmospheric content29. However, only 20% of all remaining tropical forest areas, storing ~ 40% of the above-ground tropical forest carbon stock, can be defined as “intact”30,31. Across the vast Amazon basin, for instance, intact forest areas are concentrated mainly within indigenous territories and protected areas, which collectively store some 42 GtC32. Promoting sustainable wild meat utilization, rather than the current scenario of expanding domestic livestock production across the tropics at the expense of natural ecosystems, could generate a comparatively lower carbon footprint. However, the magnitude of GHG emissions spared from consuming wild meat, rather than protein from the livestock production sector, has not been quantified. Similarly, the potential carbon credits that could be generated through, for instance, REDD + payments is unknown.

REDD + (Reduced Emissions from Deforestation and forest Degradation) is a multilateral carbon credit trading mechanism enabling polluters in usually high-income countries to pay low-income countries for reducing deforestation and forest degradation33. This was proposed to reduce carbon emissions, conserve and enhance forest carbon stocks, and sustainably manage forests to the benefit of native biodiversity. However, although the United Nations Framework Convention on Climate Change (UNFCCC) highlights the importance of co-benefits in REDD + programs34, these have generally failed to recognize and incorporate subsistence hunting and the role of wild meat in forest governance35,36.

Here, we assess the carbon footprint forgone through wild meat consumption by human populations in 49 tropical forest study sites in 22 Afrotropical and 27 Neotropical countries (see Fig. 1). We estimate the number of carbon equivalents (CO2-eq) spared through wild meat consumption compared to the alternative of consuming bovine beef and poultry—the domestic animal most likely to replace wild terrestrial game consumption across the pan-tropics under future scenarios37,38. We further estimate the carbon credit value of emissions forgone using two scenarios: (A) the price necessary to provide incentives to reach the objectives of the Paris Agreement by 2030, and (B) a conservative carbon price. We find that wild meat consumption is associated with substantially reduced carbon emissions from the livestock production sector. Arguing that the sale of carbon credits based on carbon emissions forgone from livestock production can generate incentives to enhance tropical forest resource monitoring and management, we suggest that verifiably sustainable subsistence consumption of wild meat should be incorporated into future REDD + compensation schemes and climate change mitigation efforts.

## Results

### Wild meat consumption profiles

A total of 250 terrestrial taxa were harvested across all 49 study sites, including 27 species in the Amazonian and 22 in the Afrotropical region. Mammals and birds were the most prevalent vertebrate classes in the harvest profiles, accounting for 64% and 27% of the numerical harvest across all sites, respectively. The total harvested biomass recorded by all studies represents 867,228 tons of undressed carcasses (mean ± SD = 17,698 ± 33,092 tons per site). This harvest corresponds to a biomass of 132,806 tons of animal protein (mean ± SD = 2,710 ± 5,671 kg per site), contributing to the nutritional health of the 150,882 people inhabiting the 49 sites. Mean (± SD) per capita consumption in the sample was 41.7 ± 48.1 kg person−1 yr−1 of wild meat and 8.3 ± 9.6 kg person−1 yr−1 of protein. The aggregate biomass of undressed carcasses amounted to 345,147 tons (mean ± SD = 12,782 ± 29,316 tons per site) consumed by 8,703 people in Amazonia, and 522,080 tons (mean ± SD = 23,730 ± 36,307 kg per site) consumed by 142,179 people in the Afrotropical sites. Overall, the mean per capita annual amount of wild meat protein consumed in Amazonia (11.0 kg ± 10.4 kg person−1 yr−1) was over two-fold higher than in Afrotropical forests (5.1 ± 7.3 kg person−1 yr−1; Fig. 2a).

Approximately 95% of all consumers in our sample were below the protein threshold recommended by the FAO. Most of these consumers were residents (63%) at the study sites (subnational units; country states/departments) which were burdened by low Human Development Index (HDI) scores (Fig. 2b).

### Avoided carbon footprint through wild meat consumption

Replacing the estimated wild meat consumed by residents across all study sites by an equivalent biomass of undressed domestic animal meat would produce additional emissions of ~ 71 MtCO2-eq yr−1 given a bovine beef substitution scenario. These emissions would, however, be an order of magnitude lower at ~ 3 MtCO2-eq yr−1 should wild meat be replaced with poultry (Fig. 3). The avoided GHG emissions due to wild meat consumption was on average 1 MtCO2-eq yr−1 per site (± 3 MtCO2-eq) if replaced by bovine beef, but only 0.076 MtCO2-eq yr−1 per site (± 0.173 MtCO2-eq) if replaced by poultry. Using the 95% lower and upper confidence limits of these estimates, we calculated a 23–52 fold change in MtCO2-eq yr−1 and 0.124–twofold change in MtCO2-eq yr−1 for the bovine beef and poultry scenario, respectively. Breaking down avoided emissions to the level of individual consumers, the additional carbon footprint from the livestock sector would increase by 474 kgCO2-eq yr−1 per capita if local residents shifted their dietary intake to bovine beef. However, these emissions would be only 8.76 kgCO2-eq yr−1 per capita under a poultry substitution scenario.

### Future market-based transactions in carbon credits

Using the most optimistic Scenario A (US$50 per tCO2-eq), aiming to provide incentives to reach the objectives of the Paris Agreement by 2030, the income accrued from selling carbon credits derived from avoided GHG emissions—if the entire population across the study localities continues with the current consumption of an equivalent amount of wild meat rather than bovine beef—could potentially generate US$3,579,534 yr−1 across all sites. Site-level carbon credit values ranged from a minimum of US$1278 yr−1 to a maximum of US$1,062,091 yr−1. The alternative scenario of replacing wild meat with poultry would generate much lower carbon credits, equivalent to US$185,821 yr−1 across all sites, ranging from US$66 yr−1 to US$55,135 yr−1 per site. Our more conservative carbon credit price estimates (Scenario B; US$20.81 per tCO2-eq) could potentially generate US$1,489,802 yr−1, ranging from a minimum of US$532 yr−1 to a maximum of US$44,402 yr−1 for bovine beef. For poultry, these values would amount to only US$77,338 yr−1 across all sites, ranging from US$27 yr−1 to US$22,947 yr−1 per site (Fig. 3).

## Discussion

Our results highlight that replacing wild meat consumption by forest dwellers across the tropics with domesticated animal protein sources would massively increase the global human carbon footprint through additional emissions from the livestock sector. These estimated emissions forgone are conservative because they do not consider net carbon budgets beyond the farm gate. On the other hand, carbon emissions from manufacturing essential equipment for hunting activities (e.g. ammunition, shotgun, small motor vehicles) are not considered here. Moreover, protein replacements assuming purchases of domesticated meat have already been shown to be financially unfeasible for consumers in both Amazonian3 and Afrotropical forests39, who typically represent rural poor extractivists. Beyond the carbon footprint and nutritional implications, replacing wild meat as the leading source of protein would profoundly affect local economies and social customs through the symbolic value of wild meat in traditional cultures40. Our results further strongly suggest that managing forests for their carbon storage function, the primary objective of REDD +34, needs considerable rethinking. Quantifying and monitoring standing above-ground carbon stocks in the phytomass alone fails to consider the complex trophic interactions and dependence on wild game for food and income by millions of people outside the wage-labour sector of regional economies36.

Average per capita consumption was 41.7 kg of wild meat per year, corresponding to an average daily intake of 23 g of protein per person−1, representing 41% and 46% of the recommended per capita daily amount of protein required for adult men and women, respectively41. In only 37% of all sites, the local population consumed wild meat protein that either matched or exceeded the minimum protein consumption threshold recommended by FAO (7.3 kg person−1 yr−1). Information on other animal and plant protein sources contributing to human diets—including beef, poultry, fish and legumes—is unavailable. However, 37% of the study sites in mainland Africa and Madagascar and 26% in the Amazon failed to provide this minimum recommended amount of protein intake from wild meat alone (see Fig. 2a), amounting to 63% of all sites across all 49 sites. Geographic differences in wild meat protein consumption do not imply that wild meat intake in one tropical forest realm is less critical than in the other. On the other hand, the proportion of malnourished people is high in our dataset because we cannot reliably capture the variation in consumption between different age groups of local populations. While per capita consumption of wild game protein in Amazonia was high compared to Afrotropical sites, consumption levels in both regions were, for instance, higher than the annual per capita poultry consumption in both West Africa (where most sites were located) and South America, at an estimated 1.01 kg and 4.44 kg protein person−1 yr−1, respectively42. On a per-capita basis, wild meat consumption also exceeded bovine meat protein intake at an estimated 1.7 and 8.05 kg protein yr−1 in Central Africa and Amazonia, respectively42. Hence, although wild meat consumption alone may not ensure that protein intake match the rates recommended by FAO, wild meat remains critical in averting food insecurity and malnutrition in tropical forest regions while exerting a negligible or zero carbon-footprint beyond boat fuel, ammunition, and firearm production (but see ref. 36 for other more intangible potential implications).

Current consumption of wild meat represents spared emissions amounting to 4% of the MtCO2-eq emitted by beef production in the global bovine livestock sector serving a world population of 6 billion in 2005 (2836.8 MtCO2-eq emitted by the global scale beef production)43. This is equivalent to 0.05% of the 2018 global food supply chain, which resulted in ~ 13.7 billion metric tons of CO2-eq, or 26% of all anthropogenic GHG emissions44. To put this in perspective, this amounts to 751 Boeing-747 London—New York roundtrip flights, according to the International Civil Aviation Organization45. On the other hand, if we consider additional emissions associated with land-use change (LUC)—of 188 and 14 kg CO2-eq per kilogram of fresh bovine meat and poultry, respectively46—the spared carbon footprint from wild meat consumption would be 22% (320 MtCO2-eq yr−1) and 13% (22 MtCO2-eq yr−1) higher compared to our optimistic substitution scenario for bovine beef and poultry, respectively. These examples clearly show that maintaining healthy tropical forest game populations that can ensure sustainable wild meat consumption is an important piece of the climate change mitigation puzzle in developing countries.