How does rewilding sequester carbon?

The short answer

Rewilding sequesters carbon mainly by putting animals back to work. For decades, climate solutions built around nature focused almost entirely on plants: plant a tree, protect a peatland, restore a marsh. That's not wrong, but it leaves out half the story. Wild animals shape how much carbon an ecosystem can hold, through grazing patterns that change what grows, seed dispersal that determines which trees dominate a forest, and nutrient cycling that fertilizes everything from grasslands to open ocean. Scientists call this animating the carbon cycle: restoring the animals restores the carbon-capturing behavior of the whole system, not just the plants growing inside it.

The research behind it

The clearest evidence for this comes from a 2023 paper in Nature Climate Change led by Yale ecologist Oswald Schmitz, with 15 co-authors across eight countries.¹ The team looked at nine wildlife species and groups: marine fish, whales, sharks, gray wolves, wildebeest, sea otters, musk oxen, African forest elephants, and American bison. Protecting or restoring their populations, the paper found, could add 6.41 billion tons of additional CO₂ capture every year. That's roughly 95% of what's needed annually to hit the Paris Agreement's 1.5°C target.²

That number holds up because animals influence carbon capture in ways that are easy to miss unless you're looking for them. A handful of well-studied examples show how differently this plays out depending on the species and the ecosystem.

Whales: fertilizing the ocean from below

Whales feed at depth and surface to breathe, and their nutrient-rich waste rises with them, a cycle researchers call the whale pump. That waste is loaded with iron and nitrogen, exactly what phytoplankton need to grow. Phytoplankton blooms fueled this way absorb an estimated 37 billion metric tons of CO₂ annually worldwide, according to NOAA Fisheries, and healthy whale populations measurably boost that productivity.³ Whales also store carbon directly in their bodies for the length of their long lives, and when they die naturally, their carcasses sink and lock that carbon on the seafloor for centuries, a process called a whale fall.

The IMF has put an economic figure on this: if great whale populations recovered to their pre-whaling numbers, they could capture an estimated 1.7 billion tons of CO₂ annually, valuing the current global whale population at more than a trillion dollars for carbon capture, fisheries support, and tourism combined.⁴

Forest elephants: gardeners of the Congo Basin

African forest elephants do the opposite of what you'd expect from an animal that knocks down trees. As they move through the Congo Basin, they thin out fast-growing, low-density trees and disperse seeds from more than 100 species, favoring slower-growing trees with denser wood, which store more carbon per tree. A 2019 study in Nature Geoscience, led by Fabio Berzaghi, modeled what happens as elephant populations continue to decline: central African forests could lose up to 3 billion tons of stored carbon if forest elephants disappear.⁵ Forest elephant numbers have already fallen more than 90% over the past century, mostly from poaching and habitat loss.

Bison: rebuilding grassland and soil carbon

Grasslands store most of their carbon underground, in roots and soil rather than in visible plant growth, and grazing animals play a direct role in how much carbon accumulates there. One of the clearest real-world examples comes from Romania's Tarcu Mountains, where European bison were reintroduced starting in 2014. Researchers working with Yale's Oswald Schmitz found that a herd of around 170 bison, grazing across roughly 19 square miles, could capture an additional 59,525 tons of carbon per year compared to the same land without them.⁶ The effect comes from grazing patterns that shift plant composition and boost how efficiently that landscape cycles carbon into the soil.

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