Trophic rewilding to animate the carbon cycle

The report argues that wild animals have a material influence on the carbon cycle through grazing, predation, nutrient redistribution, trampling, soil disturbance and ecosystem engineering. Although animals hold only 0.3% of global biomass carbon, experimental evidence shows they can drive 15–250% differences in carbon stored in plants, soils and sediments relative to systems without them. Examples include grazing-driven fire suppression by wildebeest in the Serengeti, where restoring populations increased storage by 4.4 MtCO₂, and trophic cascades driven by sea otters, wolves and sharks. Marine fish may add 5.5 GtCO₂ yr⁻¹ through contributions to ocean carbon fluxes.

These findings suggest that wild animals can help close the 0.5–1.5 GtCO₂ yr⁻¹ shortfall in current natural climate solutions. The authors call for recognising animal functional roles as central to climate strategies.

Changing the current mindset

Current natural climate solutions primarily target plants, soils and sediments, assuming they dominate ecosystem carbon dynamics. However, mammals and fish can influence carbon density by shaping vegetation structure, nutrient cycles and fire regimes. For example, in Guyana, tree and soil carbon increased 4–5 times across gradients of mammal species richness. The report recommends integrating animal functional roles into natural climate planning rather than treating conservation and climate objectives as competing land uses.

Research needs

Carbon impacts of many species remain uncertain because studies often measure only parts of the carbon cycle. Understanding requires whole-ecosystem carbon accounting (NECB) and assessments of how species affect different plant life stages. Population density effects may be linear or non-linear; for instance, elephants have negligible carbon impacts at <0.25 km⁻² but negative effects beyond 4 km⁻².

Further research should incorporate functional traits, species interactions and spatial variation. Modelling combined with empirical studies is needed to predict outcomes and avoid overstating carbon benefits. Methane emissions from large herbivores also require accounting; restoring wildlife to pre-industrial levels could add 327.6 MtCO₂e yr⁻¹, though these emissions may be outweighed by increases in carbon storage.

Expanding natural climate solutions

Forests represent only 9% of Earth’s surface, yet dominate natural climate solution strategies. Because animals occur across all ecosystems, trophic rewilding can broaden the spatial reach of climate mitigation. Examples include elephants in tropical forests, bison in North American prairies, muskox in Arctic ecosystems and whales in the Southern Ocean. Many candidate species (illustrated in the report’s global map) lack quantified NECB estimates but have documented functional roles.

Functional intactness—where species and densities approximate historical conditions—is present on only 2.8% of land but could rise to 54% by rewilding a small number of species. Wildlife populations can recover quickly with supportive governance, as shown by mid-twentieth-century rebounds of European mammals and birds.

Including human–nature coexistence

Most landscapes capable of supporting large-scale carbon impacts lie outside protected areas and are inhabited by people. Successful rewilding requires participatory governance, acknowledgement of local livelihoods and culturally appropriate management to avoid conflict. Coexistence landscapes allow shared use of land while maintaining ecological function, offering an alternative to exclusionary approaches such as large-scale afforestation.

Policy implications

Current frameworks, including REDD+, overlook the role of animals in sustaining carbon-rich ecosystems. This poses risks, particularly in tropical forests where overhunting leads to “empty forests” lacking key seed dispersers. The report recommends explicitly incorporating animal impacts into carbon accounting, monitoring and verification.

Trophic rewilding could provide 6.41 GtCO₂ yr⁻¹ in negative emissions, meeting 64% of the current global natural climate solutions target. Protecting and restoring animal populations—on land and in the ocean—could accelerate carbon removal and support biodiversity goals under the Paris Agreement.