The animals that are
quietly saving the climate

The Pacific coast of British Columbia was once fringed with dense kelp forests stretching for hundreds of kilometres. Kelp is among the most productive ecosystems on Earth — growing up to 60 centimetres per day, absorbing carbon dioxide at rates that dwarf those of tropical rainforest per unit area, and providing habitat for hundreds of species from lingcod to humpback whales.

When European fur traders arrived in the 18th century, sea otters were hunted almost to extinction. By 1900 the global population had collapsed from perhaps 300,000 animals to fewer than 2,000. The consequence was not immediately obvious. The kelp forests began to disappear, but the cause was attributed to water temperature, pollution, and fishing pressure. The otter connection took decades to establish.

Sea urchins eat kelp. In a healthy ecosystem, otters eat sea urchins, keeping their populations in balance. Without otters, urchin populations exploded. They grazed kelp holdfasts to the rock, creating what oceanographers call “urchin barrens” — stretches of bare seabed that had once been cathedral forests of swaying fronds.

Where sea otters have returned — reintroduced along parts of the British Columbia coast from Alaskan populations in the 1960s and 1970s — the transformation has been striking. Kelp forests have regrown. The species that depend on them have followed. And the carbon cycle has re-engaged: kelp absorbs CO² from surface water as it grows, and when kelp fronds break off and sink to the ocean floor, they take that carbon with them into long-term storage.

The challenge on the BC coast is not ecological but political. Commercial shellfish fisheries — sea urchin, crab, abalone — compete directly with recovering otter populations. The otter is simultaneously a conservation success and an economic inconvenience. The carbon value of the kelp it protects does not appear in any fishing industry balance sheet.

The world’s longest fence runs for 5,614 kilometres across the Australian interior. Built in the 1880s to protect sheep from dingo predation, it bisects the continent and has created, entirely by accident, the world’s most striking ecological experiment. On one side of the fence: dingoes. On the other: no dingoes.

The difference is visible from space.

The dingo-free side of the fence supports dramatically higher kangaroo populations. Kangaroos are efficient grazers — in the absence of any predator to make them wary or keep them moving, they concentrate on the most palatable grasses and graze them to the root. Native grass cover declines, the topsoil that grass roots hold in place becomes exposed to wind and sun, and the slow process of desertification begins.

This is not desertification caused by climate change. It is desertification caused by the removal of a predator and the unchecked population growth of its primary prey.

Researchers who have compared matched sites on either side of the dingo fence have consistently found that the dingo-present side has more diverse vegetation, more small mammals, better soil structure, and higher soil carbon. The dingo does not just suppress kangaroo numbers — it changes kangaroo behaviour. Prey animals in the presence of predators avoid lingering in open areas, keep moving, and allow vegetation to recover between grazing events. This “landscape of fear” effect is as important as direct predation.

The implications for Australia’s carbon accounts are significant. The continent holds vast areas of degraded grassland and shrubland that have lost substantial fractions of their original soil carbon. Conservative estimates suggest that restoring healthy predator-prey dynamics across even a fraction of this area could sequester tens of millions of tonnes of CO² annually — at negative cost, since the alternative involves expensive and ineffective kangaroo culling programmes.

In 1995, fourteen grey wolves were captured in Canada and released into Yellowstone National Park. They were the first wolves in the park since the last pack was eliminated in 1926. What happened next is one of the most remarkable ecological stories of the 20th century — and one of the clearest demonstrations of how a single species can reshape a landscape at a scale that no human intervention could replicate.

The park’s elk population had grown unchecked for seventy years. They grazed riparian areas — the strips of vegetation along riverbanks — intensively, stripping willows and aspens to bare twigs. Without deep-rooted vegetation, riverbanks eroded. Rivers widened and became shallower. Beaver, which depend on willows for food and dam construction, had largely disappeared.

Within a few years of the wolves’ return, something unexpected was happening. The elk were not simply being eaten in larger numbers — their behaviour was changing. They began to avoid open valleys and riverbanks, where wolves could run them down. The “landscape of fear” that the wolves created was reshaping where elk chose to spend their time.

In the areas the elk abandoned, vegetation recovered rapidly. Willows and aspens grew tall enough to shade the rivers. Beavers returned to build dams. The dams slowed river flow, raised water tables, and created wetland habitats. Songbird and beaver populations increased. And the rivers — the physical rivers themselves — began to meander differently, with more stable banks and deeper channels.

Yellowstone is one example, but wolf reintroductions across Europe — in Poland’s Bialowieza Forest, in the Italian Apennines, gradually expanding into France and Germany — are producing similar effects at different scales. Each recovery is slower and messier than the Yellowstone narrative suggests, complicated by livestock predation and human conflict. But the ecological direction is consistent.

Whales are not predators in the trophic cascade sense — they do not suppress their prey to protect a lower trophic level. But they are architects of ocean carbon cycling in a way that makes them among the most important organisms on Earth for climate regulation, and one of the most overlooked.

The mechanism is indirect but powerful. Great whales feed at depth, then surface to breathe — and to defecate. Whale faeces are extraordinarily rich in iron and nitrogen: exactly the nutrients that limit phytoplankton growth in large stretches of the open ocean. Whales effectively act as a nutrient conveyor belt, bringing deep-ocean minerals to the sunlit surface layer where photosynthesis can use them. The resulting phytoplankton blooms absorb atmospheric CO⊂2; when the phytoplankton die, most sink to the ocean floor, taking that carbon with them into storage measured in centuries.

This is called the “whale pump.” It was diminished dramatically by commercial whaling, which removed an estimated 3 million great whales from the oceans over the 20th century — along with all the nutrient cycling they would have performed. Estimates of the resulting reduction in ocean carbon capture vary, but they are very large.