Return of the giants: How rewilding megafauna is reshaping resilient ecosystems

Many of us grew up envisioning (or dreading) a world with giant mammoths or ferocious saber-tooth tigers. While recreating a world of historic predators might sound straight from Jurassic Park, it is not as far-fetched as it seems — and according to UBC researchers, it could help restore balance to ecosystems that are spiraling towards extinction.

Researchers at the Connecting Human and Natural System (CHANS) Lab have been working on rewilding: an ecological concept referring to the introduction of megafauna to restore ecological equilibrium.

Megafauna refers to species like grizzly bears, which settlers evicted from their North American native ranges, more than it does dinosaurs. Still, bringing back huge animals that have been absent from their historic habitats for decades is a complex process that can be controversial.

People drove megafauna to extinction

Megafauna includes animals above specific weight thresholds. Megaherbivores, such as elephants and hippos, weigh over 1,000 kg. Among carnivores, there are megacarnivores (100+ kg) and large carnivores (21.5 — 99 kg). Megafauna include aquatic and marine species, but extinction mainly impacts continental species as deforestation and hunting become widespread.

To address the worsening crisis in biodiversity, , the years 2021 to 2030 have been declared the United Nations Decade of Ecosystem Restoration. The CHANS Lab theorizes that rewilding can play a part in restoring equilibrium to ecosystems that may have been out of balance for thousands of years longer than many people imagine.

Dr. Kai Chan, head of the CHANS Lab, likened the rapid human-caused extinction of megafauna to Noah’s Ark, with a human hand pushing off the animals “one by one.”

With the increasing intensity of human activities worldwide, only 9 out of 50 megaherbivores and 6 of 15 species of megacarnivores remain from the Late Pleistocene

— when the ice sheets receded, about 11,700 years ago. The end of the glacial period coincided with the mass extinction of megafauna, due to a combination of hunting by humans around the world and to environmental change.

Now, human activities under the economic structure of fossil fuel capitalism are again causing an extinction crisis, with around 1 million species of animals and plants endangered worldwide. In the words of 19th-century biologist Alfred Russel Wallace, we are living in “a zoologically impoverished world.”

Through rewilding, researchers at the CHANS Lab aim to understand the impacts of restoring top predators to ecosystems that they once shaped. The researchers emphasize trophic rewilding, a strategy for ecological conservation.

“[Trophic rewilding] is managing the process of bringing animals back into ecosystems, where they can fulfill ecological roles that were part of those co-evolved systems,” said Chan.

Grizzly bears on the rebound

In the forests of the Pacific Northwest, a top predator is missing. While most hikers would enjoy the absence of grizzly bears, to ecologist Anna Santo, it’s a sign that forest ecosystems aren’t functioning as they should be.

Grizzly bears’ immense size allows them to dramatically alter the landscape. They transport animal carcasses, move nutrients in the soil and impact wildlife movements through hunting and migration.

Rewilding researchers call impactful megafauna like grizzlies “ecological engineers.”

Santo, a CHANS lab researcher and PhD candidate at UBC’s Institute for Resource, Environment and Sustainability (IRES), is studying the rewilding of grizzly bears in the mountainous North Cascades in Washington state. Grizzlies have been deliberately removed, what ecologists call “extirpated,” from the North Cascades up into BC since the 1990s..

In Washington, rewilding proposals are slowly unfolding. In September, the US National Parks Service released an Environmental Impact Statement for 2 potential pathways to gradually reintroduce 25 bears into the ecosystem. They’re currently asking for public comment, to gauge public support for a potential new population of carnivorous neighbors.

For people who live near ecosystems where megafauna once lived and could live again, rewilding can seem threatening.

Santo said local communities are often concerned about the presence of grizzly bears near their homes and farms, as the bears can kill livestock near the rewilding boundaries.

Chan recalled a project of rewilding sea otters at Clayoquot Sound. Contrary to expectations, the project dismayed many locals, who called the otters “floating fleabags” because they ate valuable shellfish.

Santo is also worried about the well-being of rewilded animals.

“Is this a humane [and appropriate] thing to do to translocate bears from a place where they are currently living into a new home that might be unfamiliar to them?” she said.

Alberto Campos, a CHANS Lab researcher and PhD candidate at IRES, similarly advocated for considering rewilding from the animals’ perspectives.

“Some people say, ‘Oh, let’s reintroduce [the animals] and they will find a way to survive.’ It’s not like that … you have to respect the animals that you are introducing and give them good conditions … not just to survive, but to thrive and reproduce,” Campos said.

Since bears don’t know national borders, once returned to their native range in Washington, they could also travel north to BC.

“The potential impacts might include bears dispersing from the habitat in Washington and to British Columbia, where they’re also considered to be extirpated,” said Santo.

Currently, grizzly bears have not returned to the Canadian portion of the ecosystem, but hopes remain that their rewilding will follow the footsteps of other successful examples, such as reintroducing wolves to Yellowstone National Park.

Rewilding from BC to Brazil

Campos is conducting fieldwork at a farm in Canindé, a small town south of Fortaleza, Brazil. He focuses on rewilding in the Caatinga, a partially arid type of forest only in Brazil. By prioritizing clean water sources, he aims to restore the habitats of rewilded species during the dry season when rain is scarce.

One such species is the rhea, a large bird related to the ostrich that lives on open landscapes, such as clearings in the Caatinga. Feeding on seeds, rheas are crucial in dispersing native cashews. Rewilding the rhea can reintroduce disappearing native cashew trees to the Caatinga, emphasizing the interconnection between megafauna and flora.

As the climate crisis puts more stress on ecosystems, rewilding megafauna is more essential than ever to re-establish ecological balance.

“This [world] is a fraction of what was given to us ... We have the duty and the responsibility to restore part of this diversity,” Campos said.

“[The] planet needs diversity … It’s like oil for the planet, [like] an engine … You need it to make it work more smoothly, more productive. And at one point, if there’s a very small amount of diversity, this engine may stop, and then it will be really difficult for us.”